Chapter 2 Cycloolefin monomers. Types and syntheses

15

Chapter 2 CYCLOOLEFIN MONOMERS. TYPES AND SYNTHESES

A great number of cycloolefms have been used as monomers in the vinyl and ring-opening metathesis polymerization reactions using different catalytic systems. They pertain to monocycfic, bicyclic and polycyclic olefins, with or without substituents. Whether a cycloolefin is prone to vinyl or ring-opening p o l ~ o n , this propensity is a matter determined primarily by the nature of the catalytic system employed. However, the nature of the monomer can be quite effective in directing the polymerization reaction towards the first or the second type of polymerization. In most ~ , hydr~n compounds have been employed as monomers in these reactions. Cycloolefins bearing functional groups constitute, however, a special class of the starring materials. As the nature of the catalytic system and the reaction conditions are essential for directing the process towards the vinyl or ring-opening polymerization of cycloolefins, these monomers will be presented separately for the two types of process. Cycloolefins suitable for cationic, anionic and Ziegler-Natta coordination polymerization will undergo addition p o l y m ~ o n yielding poly(cycloolefin)s by opening the cat.n-carbon double bond of the monomer. As the catalytic properties of the corresponding catalysts vary drastically, ranging from pure cationic to anionic systems, the nature of the cycloolefin has to be carefi~y considered so that the atfmity of the polymefizable ~ n - c a r b o n double bond towards the catalyst be good enough that the p r o s be initiated. Taking into ~ u n t the different types of catalyst that can be employed in the cycloolefin polymerization, the monomers will be grouped into the following c l ~ : (i) monomers for cationic polymerization, (ii) monomers for anionic polymerization, (iii) monomers for Ziegler-Natta coordination polymerization and (iv) monomers for ring-opening metathesis polymerization.

16 2.1. Monomers for Cationic Polymerization.

It is a requisite for the cationic polymerization that the monomer should possess carbon-carbon double bonds having enough nucleophilicity so as to interact with the cationic species and promote both the initiation and propagation processes by a cationic pathway. In order that this reaction to occur, the cycloolefin has to contain electron-rich double bonds having high affinity towards the cationic species from the system. In this category we shall find simple, unmbst~ted and substituted cycloolefins, cyclodienes, bicyclic and polycyclic olefms. The substituents are generally alkyl or aryl groups, having an electron donating character, but also some specific donating functional groups of a low nucleophilicity, which will not interact with the cationic species, will be appropriate. It is of interest to note that a large number of unsubstituted and substituted cycloolefins possessing various degrees of unsaturation and structures from monocyclic to polycyclic monoenes, dienes and polyenes, have been used as monomers in cationic polymerization. I Some of these monomers served as starting materials for extensive kinetic and mechanistic studies while others have been fruitfully employed for important applications like manufacture of hydrocarbon resins or other chemical products. 27 In Schemes 2.1-2.3 we shall compile several monomers for which the cationic polymerization reaction has been described' whereas certain particularities for the polymefizztion reactions will be presented in the next chapters. These

o,o ,o cp c / o cr p p-,Q

Scheme 2.1

17 monomers can be grouped into the class of monocyclic and bicyclic olefi~ stemming from petrochemical sources.

0 0,, 0 Cr. 0

10

Schen~ 2.2

I

Scheme 2.3

18 2.2. Monomers for Anionic Polymerization

Simple, unsubstituted cycloolefi~ will be reluctant towards the anionic catalysts due to the lack of reactivity of the nucleophilic carbon~n double bond under these conditions. However, if appropriate electron withdrawing substituents, particularly functional groups, will be attached to the cycloolefin so that the basicity or nucleophilicity of the carbon-carbon double bond be diminished, substituted cycloolefins might become proper monomers for anionic polymerization. Such monomers, in the presence of anionic initiators, will lead to ~ o n a l i z e d polymers having interesting properties, related to the current functionalized polyolefins. Functional groups such as nitrile, ester, ether, halogen, etc., attached to the cycloolefins in certain positions, will be able to render the carbon-carbon double bond anionically polymefiz~le and produce polymers by addition polymerization with specific stnJctures and properties (Scheme 2.4). CN

COOR

COR

CONHR

Scheme 2.4

A special class of monomers for anionic polymerization is formed by heteroatom-containing unsaturated cyclic compounds, e.g., sila~cloalkenesS" ~2(Scheme 2.5).

O<"CH3 ps C., O<:"' ~ xCH3 6H5 i,-CSHs "CsHs

CS

< Scheme 2.5

19

2.3. Monomers for Ziegler-Natta Polymerization Both cationic and anionic coordination r as well as conventional Ziegler-Natta ~ y s t s will promote r polymerization once the monomer is able to coordinate and polarization of the coordinated monomer will allow subsequent insertion into the metalcarbon bond. In the fu~ case, in order that the coordination to occur at these types of catalytic systems, it is important that the nucleophilicity or electrophilicity of the carbon-carbon double bond to be high enough in order that the interaction with the cationic or anionic species of the ~ y s t to be possible. However, these two affinity parameters of the ~ n - c a r b o n double bond will be substantially determined by the existing substituents on the cycloolefin through their electron donating or withdrawing propensity. In the case of non-ionic coordination catalysts, the coordination process will be governed by the coordination ability of the cattalyst as a fire.on of the nature of the metal involved in the formation of the active species. As the variety of coordination catalysts of the Ziegler-Natta type is rather vast at present, a wide number of cycloolefu~ have been used in such polym~on reactions, their study being of a particular ac~emic and industrial significance. Simple, unsubstituted cycloolefins like cyclobutene, cyclopentene, cyr cyr etc. have been employed as monomers in early studies carried out by Natta and coworkers on the polymerization reactions with catalytic systems based on the transition metal derivatives and organometallic compounds 13"~6(Scheme 2.6).

n O 0

0

OQ

0 Scheme 2.6

20 Bicyclic and polycyclic olefins, e.g., norbornene and dicyclopentadiene, form an interesting class of monomers that have been fruitfully employed with various coordination catalysts due to their pronounced reactivity and highly performant characteristics of the products o b t a i ~ (Scheme 2.7).

Scheme 2.7 Recently, such monomers have been extensively employed in the copolymerization reactions with unsubstituted or substituted olefins linear olefins to yield new products having excellent mechanical, optical and electrical properties. ~s~2~ Substituted cycloolefins afford another class of monomers with a high potential in the polymerization and copolymerization reactions induced by coordination catalysts due to the special properties that the substituents will impart to the products obtained. In order that the coordination of the cycloolefin at the active site to ocx~r, it is a prerequisite for the substituents to be attached at distant positions with respect to the carbon-carbon double bond. Moreover, it is necessary that the nature of the substituents be so that their comvlexation with the catalyst to favor the insertion process.

21 Hydrocarbon substituents like alkyl and aryl groups are generally the preferred substituents in monocyclic or polycyclic olefins but also mild functionality, that will not interact with the coordination center, will be possible. Examples of such substituted monomers are 3-methylcyclobutene, 4-~ylcyclopentene, 5-methylnorbornene, 7-methylnorbornene etc. and a large number of monocyclic and polycyclic olefins bearing linear or branched alkyl or awl groups as far as possible with respect to the ~ n carbon double bond. ~~ They are of a partic~ar utility in copolymerization reactions where the presence of substituents in the cyclic recurring unit impart special physical-chemical properties to the obtained products.

2.4. Monomers for Ring-Opening Metathesis Polymerization So far, a wide range of unmbstituted and substituted cycloolefms have been employed as monomers in the ring-opening metathesis polymerization. 6 The cycloolefins pertain generally to monocyclic structures, they possess one or more degrees of unsaturation or may be of a more complicated architecture of the bicyclic or polycyclic type. The substituents are primarily a hydrocarbon group such as alkyl, cycloalkyl or aryl radicals. Functional groups are also possible as substituents at the parent cycloolefin or attached to the h y d r ~ o n radical but only when appropriate tolerant catalysts are used. Taking into ~ n t the cyclic nature of the starting olefin and the type of the substituents, the monomers for ring-opening metathesis polymerization will be divided into the following three groups: (i) monocyclic olefins, (ii) bicyclic and polycyclic olefms and (iii) monomers with functional groups.

2.4.1. Monocyclic Olefms for Ring-Opening Metathesis Polymerization

Due to their easy availability, u n s u b ~ e d monocyclic olefu~ have been largely used as advantageous monomers for ring-opening metathesis polymerization in the presence of a wide range of catalytic systems. ~l'z3 Of these monomers, cyclobutene, cyclopentene, cyclooctene, cyclodecene and cyclododecene have been s u ~ y p o l ~ under various reaction conditions to prepare polymers that can be widely applied for their practic~ properties. By this procedure, valuable polymers like polybutenamer,

22 polypentenamer and polyoetenamer have been successfully manufactured, zt'zs Higher unsaturafion is also encountered in several monomers like 1,5-cyelooetadiene, 1,5,9-eyelododecatriene and cyelooctatetraene or other cyclic structures, ~'3~ the unsaturation degree having an influence on the catalytic system and the reaction conditions (Scheme 2.8).

n C> (-)

( }

( } ! C''O Scheme 2.8

Substitution of monocyelic olefins with linear or branched alkyl and aryl groups provides useful monomers for the ring-opened polymers with particular structures and properties. It is essential that the substituents have to be attached at distant position with respect to the ear.n-carbon double bond in order to diminish the steric hindrance during the initiation and propagation processes of the ring-opening polymerization. Interesting examples are 3-methylcyclobutene, 4-methylcyclopentene, 4isopropylcyclopentene and several other alkyl- and aryl-substituted cycloolefins that have been polymefz~ in the presence of specific ringopening metathesis catalysts to the respective ring-opened polymers 2~'3~ (Scheme 2.9). In these monomers the distant substituent will not interfere with the active site in such a way as to hinder the initiation or propagation reaction. Importantly, if these substituents are attached directly at or in the vicinity of the carbon-ca~on double bond of the monomer, the polymerization reaction is strongly inhibited.

23 Rx

!11

R

1

/

III

!1 I

R

/ R

il I\ R

O

/

~

Alkyl

Ph

Scheme 29 2.4.2. Bicyclic and Polycyclic Old'ms for Ring-Opening Metathesis Polymerization Due to their high reactivity in this type of reaction, norbomene and substituted norbornenes represent a large group of bicyclic olefi~ that have been extensively applied in ring-opening metathesis polynmrizalJon. 31"3s Different alkyl radicals, e.g., methyl, ethyl, propyl, butyl, etc., have been attached in various positions of the norbomene skeleton leading to polymers with different structures and properties, depending on the substituent (Scheme 2.10). The re,activity of the substituted norbomene will change substantially as a function of the nature and position of the substituent. ~u~ In the same way, norbomadiene and substituted norbomadienes 3~9 offer another group of monomers for ring-opening polymerization providing related polymers of a higher unsaturation

24 degree which can be further processed and transformed into new products having totally different physical properties (Scheme 2.10).

Scheme 2.10

Many monomers of interest are derived from a large series of bicyclic, tricyclic or polycyclic hydrocarbons such as bicycloheptene, bicycloheptadiene, bicyclooctene, bicydooctadiene, 4~ indene," bicyclononadiene, benzvalene, ~s deltacyclene, ~ barrelene, benzobarrelene, ~ paracyclophene, 47 fullerene and their derivatives a (Scheme 2.11). It is worth mentioning that one of these monomers, indene, ~ which was widely employed as a cationic substrate, will produce by ring-opening polymerization products with interesting electrical properties. Benzvalene (5 and cyclophene 47 will also produce by ring-opening polymerization good precursors for highly unsaturated polymers with special electrical properties. Several benzo derivatives of various bicyclic and polycyclic monomers will lead to polymers with benzene moieties in the

25

reoming units, what will afford special properties, e.g. heat resistance, to the products obtained. +9 Finally, a norbornene derivative of fidlerene" will be able to introduce this particular stmcaue as a recurring unit in the polynorbomene chain by ring-opening polymerization reaction."

Q

Scheme 2. l I

26 Dicyclopentadiene has been extensively employed as an attractive monomer for ring-opening metathesis p o l y m ~ o n to produce highly appreciated linear and cross-linked products s~ (Scheme 2.12). Important industrial procedures for manufacture of poly(dicyclopentadiene) have been developed starting from this monomerss. Dihydrodicyclopentadiene is also a suitable monomer for the ring-opening polymerization reaction to linear polymers. Due to the absence of unsaturation in the condensed cycle, cross, linking is not possible and linearity of the polymer chain can thus be conveniently controlled. The next higher oligomer of the series, tricyclopentadiene, presents also unsaturated functionality similar to dicyclopentadiene leading by ring-opening to poly(tricyclopentadiene), able to cross-link.

Scheme 2.12 A great number of norbomene-like monomers available for ring-opening metathesis polymerization can be obtained by Diels-Alder method from norbomadiene and various substituted or unsubstituted dienes. ~s Using this class of monomers, a wide range of special ring-opened polymers with excellent mechanical and optical properties have been prepared . ' ~

27 2.4.3. Monomers with Functional Groups

Functional groups, when present in the cycloolefins, provide new sites of a t ~ t y towards the catalysts so that under these circumstances only a limited number of c,s~ysts will allow the polymerization p r ~ to ocxa~. In early explorations of the ring-opening p o l y m ~ t i o n , the reaction has been successfully applied to many monomers bearing specific fiu~onal groups like esters, nitrile, halogen etc. Recently, the re,action has been extended to monomers bearing a wide range of functionalities 2 (Scheme 2.13).

COOR

CO

CO

OOR

/ CO

/ N-CH2Ph CO

[~COOR QOH

[~Y--COOR OCOOR

~~

.CI

~

t OR CN

,/BR2

OCN

O ~~

CH~C,

BEt2 ICF3 CONH2

,,o oo.

~ ~

--CN

CH2CN

sicl,

Scheme 2.13

~

Si(OCH3)3

28

Thus, norbomene monomers, substituted with ester groups, cyan or halogens in the 5- or 7-position, have been frequently used in the ringopening metathesis polymerization in the presence of various catalytic systems. At the same time, as it has been observed in monocyclic olefu~ containing fimctional groups in the distant positions with respect to the carbon-carbon double bond, these functionality wig not hinder the accx=ss of the polymerizable double bond at tl~ active center. In this way, monomers like cyclopentene, cyclooctene, cyclononene, cyclodecene and c y c l o d o d ~ e substituted with ester, nitrile, halogen groups in remote positions have been s u ~ f u l l y polymerized under the action of the catalysts that tolerate such fimctional groups. Polycyclic olefins bearing functional groups constitute a special class of monomers for ring-opening metathesis polymerization. The majority of this group of cycloolefi~ have a norbomene-like structure and, unless the presence of the functional group will affect the carbon-carbon double bond and the catalytic center, the polymerizability is rather high due to strain relief and relatively diminished steric hindrance. Thus, a wide series of fluorine substituted norbomenes and related cyclic olefins have been employed as monomers in the ring-opening polymerization reaotion 61'62 (Schemes 2.14 - 2.15).

F

C5F11

~CF3

C~CF F3

F3

C~F3 F

~ C

F 2F5

Cl~

F3 F3 CeFs

CF3 F3 Schen~ 2.14

C4F9

CF3 CF3

29 Fluorinated polymers with.good mechanical and physical properties can be obtained conveniently ,by this route and find interesting pra~cal applications. It is worth mentioning that the fluorine atom may be introduced directly in the bicyclic skeleton or in the attached substituent as can be seen from Scheme 15. Some rich fluorine containing monomers have the fluorine atoms in both positions. Of a special interest are the fluorine containing monomers for polyng~ precursors of polyacetylene prepared by the Durham route ~2 (Scheme 2.15).

i~

F F.F

F

F F

F

F3C~

F3C~

F

Scheme 2.15 Chlorine substituted cycloolefins of various types have been used as monomers in many ring-opening polymerization reactions~3 (Scheme 2.16).

,,,C,c,

••••-C

I

k,~ ~Cl

()-c' ~~-CI Cl

I~ qlo

#'-.Z_/.-c. #J~o-'c o Scheme 2.16

c' Cl Cl

c ~ ] ~ c ~lo

.S--'c0

30 As Scheme 2.16 illustrates the chlorine atoms are situated in a remote position with respoct to the reactive carbon-carbon double bond in order to maintain the monomer reactivity. A very wide range of oxygen-containing monomers have also been employed in the ring-opening polymerization reactions~ ~ (Scheme 2.17).

r ~ o" ~--OR

/~~f

f_i.cooa

i-[ -~

\~

~COs

,OM

i_[. c-(:x:~ ~COOI~

/~~~,ocOCOOR _1~ CO\

oo. f,L ,7-00 o,,O

R

~ , cCH2OCOCH3 H2OCOCH3

OMe OMe I

x---OMe Scheme 2.17

Among the sulphur-containing monomers, ~ alkylthiocyclooctenes and a number of norbornene derivatives appear to be well tolerated by specific metathesis catalysts (Scheme 2.18).

(y"

~ O C S _OCS--SI~ _

SI~

SMe

SIV~

Scheme 2.18 In the case of alkylthiocyclooctenes, the reactivity showed to be crucially influenced by the steric crowding at the heteroatom ( R = c-Hex, n-Hex, tert-Bu, n-Bu, Et).

31 Of a great interest are the nitrogen-c~ntaining monomers that have been fi'uiffuUy employed in a number of ring-opening metathesis polymerization reactions. ~ u This type of monomers can tolerate a wide range of met~e~is polymerization catalysts and provide polymers with good physical and mechanic~ properties. The products can be further transformed by appropriate chemical reactions to new polymers with desired properties. Some examples are illustrated in Scheme 2.19.

CON 0

'CH2--

~~CH3 0

0

0

0

0

0

0

Scheme 2.19

Monong~ containing boron, e.g., (5-cyclooctenyl)diethylborane and 5-norbomenyl-9-borabicyclononane (Scheme 2.20), have been s u ~ f u l l y used in the ring.~ning polymerization reason to produce functionalized polyalkenamers. ~

Schomo 2.20

32 The alkylborane group has been easily removed from the polyalkenamer by oxidation with alkaline H202 to the corresponding hydroxy polymer. Many silicon-containing monomers have been employed in the ringopening metathesis reactions to produce interesting polymers, having particular physical-chemic~ properties 7s'n (Scheme 2.21). slch

~OSIMe 3 ~SiMe

~Si(OMe)3 ~Si(OEt)3

~

3

~li--'-(CH2)n'

iMe2tBu

0 S i(tBu)M

-N

e 2

Scheme 2.21 Of a great potential is the use of metal-containing monomers to prepare metallated polyalkenamers by ring-opening polymerization reaction. A first series is that of cyclic monomers containing organotin moieties (Scheme 2.22). 79

sou,

~

,~.~--Sn~

SnBu, (

~~~ ,

Scheme 2.22

~

C

H

~

C

H

2

-

-

S

n

B

~

33 The monomer and the metal can be varied in a wide range to obtain polymers with good physicS-chemical properties, suitable for many applicationss~ (Scheme 2.23-2.24). /tl~

iMe~

~N? \l'b

\t~

N/

/tBu R N ~r \

Scheme 2.23

Scheme 2.24 The metals induce specific properties to the polymers which can not be attained with the conventional substituents. These speciality polymers could be applied in various electric and electronic devices. Monomers containing a nematic side group attached at the monocyclic and bicyclic olefim, e.g., cyclooctene and norbomene, have been successfully employed to prepare side-chain liquid crystalline polymers by the ring-opening metathesis polymerization re.action,wg~

34 With the discovery of quite tolerable metathesis catalysts, the side group can be widely varied and the nematic properties conveniently tuned. Several examples are offered by monosubstituted cyclooctene and norbomene with nitrile and ether containing mesogenic groups u4s (Scheme 2.25).

O0.CH2.,,O~-->l\-~_c,

~C ~~C~~OMe ~~~,CO2(C H2)~OMe

~cm
Scheme 2.25 Within a new class of norbomene derivatives reported recently,ts'.7 in contrast to their hydrocarbon analogs which lead by ring-opening

35 polymerization to nematic liquid crystalline polymers, monomers with fluorocarbon and siloxane segments will induce smectic layering in nematic liquid crystalline polymers obtained therefrom (Scheme 2.26).

CO I

.OH20

0

0

0

c~

F(CF2)m(CH2

C~--~D(CH2)n(CF2)mF

I

c~

ot3

"-"

o

~

o

~

a~

o~

Scheme 2.26

Also, dimbstituted norbornenes, bearing this class of mesogenic groups, showed to be proper monomers for side-chain liquid crystalline polymersu'=9 (Scheme 2.27).

36

CH~O_~__~O_(OH~~CO~C~~ o ~ o c ~ Scheme 2.27 Such side-chain liquid crystalline polymers are proper components for special applications in electronic devices, for optically anisotropic materials and in other related fields. Macromonomers constitute an interesting class of monomers for the synthesis of speciality polymers. Some examples include polystyryl and polybutadiene macromonomers containing a norbornene units u'ss (Scheme 2.28).

O0

OOC,~

O~ Schemo 2.28

37 The properties of the polymers obtained from ~ type of monomers are remarkable, this makes the manufacture of this kind of products very attractive for their practical applications. 2.4.4. Heterocyclic Monomers Of the class of heterocyclic o l e O , 2,3-dihydrofia~n and 2,3dihydropyran have been used as monomers for the synthesis of unsaturated l~lyethers by ring--ol~~ meta~esis polymerization (Scheme 2.29).

Scheme 2.29 The application has been extended to larger oxygen-containing heterocycles such as 7-acetoxy-4,5,6,7-tetrahydrooxepine and ambrettolide. Sila- and disilacycloalkenes are monomers of interest for the synthesis of silicon eomaining polymers (Scheme 2.30).

GC

0'. SI

Sl

|

.J

Sch~

2.30

38 These monomers are prone either for the ring-opening metathesis or for the anionic polymerization, leading to polymers containing the silicon atom along the chain or included in a cyclic recurring unit. A considerable number of bicyclic and polycyclic oxygen-containing heterocycloolefins have been used in the ring-opening metathesis polymerization to manufacture speciality polymers with a polyether structure (Scheme 2.31 ). O

O

R

2

R~

R2

0

R4 0

O

O

O

OCH2OMo O CH2OMe ~OC(=CH2)Mo OC(=CH2)Me

0

o

O

O

O

O

CN

CN

Scheme 2.31 Some of these monomers contain additional functional groups in order to impart specific properties to the respective polymers. Oxa- and aza-benzonorbomene monomers, with or without substituents, will lead by ring-opening metathesis polymerization to heteropolymers bearing benzene rings in the recurring units. In addition, a number of monomers containing the nitrogen atom in other positions than at the bridgehead position in the norbornene moiety have been

39

succ~sfully employed in this type of reactions (Scheme 2.32). N~R

0

O

R

0 NH

o Scheme2.32

R ~ f l y , heterocyclic monomers with a monodenddtic substituent have been used tO prepare polymers with particular architectures 9''92 (Scheme 2.3 3).

/

OCH2"---~

~O(CH2)I2H

--< '>-O(CH2)12H

OCH 2

OCH~ ~ ~---O(CH~),~H

~--o O

\CH 2

/

\

,/

~OCH2-~__~ O(CH2)'2H ~OCH2---~ ~--O(CH2)12H Scheme 2.33 Due to the fact that such structures can self-organize into well-defined supramolecular architectures, both before and after polymerization, these products are of a great interest for new applications in the colloid and polymer chemistry.

40

2.5. Synthesis of Monomers There is a great variety of cycloolefms that have been polymerized by one or more of the above reaction mechanisms; due to the fact that only a limited number of cycloolefins are available from natural resources, at present a large number of synthetic methods for cycloolefin production have been developed.

2.5.1. Synthesis of Monocydic Olerms Cyclopropene and substituted cydopropene. Closs and Krantz9s treated aUyl chloride with sodium amide in refluxing tetrahydrofiaan and obtained cyclopropene in about 10% yield. Cyclopropene produced in this way reacts with cyclopentadiene at 0~ to give the Diels-Alder adduct, tricyclo[4.1.0, l~4]o~-3-ene, in 10 % yield (Fxl. 2.1-2.2).

~k

CI

NaNH 2 THF, n__10%~

[}~>

(2.1)

T =(T'C = (2.2) 11---10% Similarly, Fisher and Applequist9~ reacted methaJlyl chloride with sodium amide in refluxing tetrahydrofuran to produce ]-methylcyclopropane in reasonable yield. The reaction probably involves the intermediate formation and cyclization of vinylcarbene (Eq. 2.3). +

NsNHz-.~ -Cl

~

(2.3)

THF

Cydobutene and substituted r Cyclobutene can be prepared in high yield from butadiene by photochemical isomerization97''~176 (F_.q. 2.4).

%

f

h.~ =

IF.]

(2.4)

Depending on the reaction conditions and the nature of the starting material, bicyclo[ 1.1.0]butane forms as a side-product along with two other products of intermolecular cycloaddition, 1,2.
41 4-vinylcyclohexene. High c o ~ t r a t i o n of butadiene and irradiation of pure monomer will favor formation of 1,2-vinylcyclobutane and 4-vinyle y c l o h ~ by i n t ~ l e ~ l ~ eycloa~ldRion. By exmm~ in highly diluted solutions, in hydrocarbon or ether media, and in the gas-pha.~ the reaction proceeds preferentially by an intramolecular pathway to cyclobutene. For instance, irradiation of butadiene in ethyl ether provides a mixture of r and bicyclo[l 10]butane in 7:1 ratio whereas in 2,2,4trimethylpentane the ratio of products will be 14:1 under the same conditions. :~ (I) salts favor also intramolecular cyclization reaction to cyclobuteneg~176 1,2-Dimethylcyclobutene can be prepared in 71% yield by an analogous photochemical route from 2,3-dimethylbutadiene :~ (Eq. 2.5). /

\

q=71%'~

/

.

,

(25)

Cydopenteae and Cydopeatadieae. There are several routes for the production of cyclopentene, some of them of great economical importance. ~ g e amounts of cyclopentene are obtained from the Cs stream of the steam cracking of heavy hydrocat~ns (naphtha, gas oil) whereas small scale production is provided by cyclopentane dehydrogenation, piperylene isomerization and cyclopentanol dehydration. :~:0~ Steam cracking has attained great importance in Europe and Japan as the main source of ethylene and propylene so that it is an economical source also for cyclopentene. The amount of Cs cut from a steam cracker is about 20% of the ethylene stream and its composition varies according to the cracking conditions. This fraction contains minor recoverable amounts Table 2.1 Hydrocarbm compcnition of C, cut from a stzam cracker" Cyclopmtme Dicyclopmtadime + Cyclopmtadiene Isoprene Piperylme C~ olefms Cs alkanes C, + C6 9Data fixsn referencea

i

2.5 16.5 17.0 11.5 17.0 31.0 4.5 i

42 of cyclopentene, but the principal source of this monomer would be from hydrogenation of cyclopentadiene (Table 2.1). The process for cydopentene production fTom C5 cut is based on extractive distillation with selective solvents. The solvents N-methyl-2pyrrolidone, dimethylformamide, furfural, aniline, acetonitrile and formylmorpholine, used to isolate butadiene from the C4 cut, have been proposed for cyclopentene extraction and, in some pilot plants, also applied to the recovery of dimes from the C5 cut. Acoording to a procedure developed jointly by BASF and Erdolchemie, '~ which uses Nmethylpyrrolidone as solvent, production of cyclopentene is combined with that of isoprene and piperylene (Figure 2.1). In this process, cydopentadiene is first dimerized to dicydopentadiene by heating of the Cs feedstock and, after separation and selective hydrogenation to cyclopentene, fed back to the N-methylpyrrolidone (NMP) extracts containmg the conjugated dienes and the aliquots of cyclopentene originally present in the feedstock. A further extractive distillation with Nmethylpyrrolidone, followed by fractional distillation, yields polymerization grade cyclopentene and isoprene. This combined facility is one of the most non to both rubber monomers. I'h Waste g n

Isoprene

1 11-

7

2

I Cs

Cyetoper~r~

Diobtns

Pipen~enes NMP

Higher con-r

NMP

Figure 2.1. Process for cyclopmtme and isoprene production fi'om Cs cuts (1 :Dimerization, 2 :N-Methytpyrrolidone Extraction, 3:Distillation, 4:DicyclopeRadiene Decomposition, 5-6: Cyclopm~diene Hydrogenation, 7: NMethytpyrrolidone Extraction, 8" Cyclopentene and Isoprene Separation)'~ However, also the separation of dicyclopentadiene without extraction of isoprene has been reported as an economically feasible process for cydopentene production. '~

43 By c o n ~ the method for cyclopentene synthesis from cyclopentane, which occurs usually in many petroleum fractions, by catalytic dehydrogenation is far less selective and would involve a cyclopentane facility (Eq. 2.6).

[~~

[Cat]

(2.6)

However, another route to cyclopentene, that could bocome economic under special circumstances, depending on the availability of raw material, is the gas-phase cyclization of piperylene catalyzed by hydrogen sulphide (Eq. 2.7).

[H2S]

(2.7)

Piperylene is in fact one of the major by-products of steam-cracking and of some processes for isoprene synthesis such as the propylene dimefization over methylpentene and its subsequent demethanafion. Cyclopentadiene is readily obtained by distillation of dicyclopentadiene in the presence of copper powder or iron. '~ A continuous process for the depolymerization of dicyclopentadiene was described in the patent literature. ,09 An important amount of cyclopentadiene is produced by high temperature pyrolysis of hydrocarbons. By this way, cyclopentadiene is formed in cracking gas, natural gas, oil distillates. Two synthetic methods are most largely applied for the manufacture of dicyclopentadiene: (i) ~ y t i c dehydrogenation of cyclopentene and (ii) cyclization of piperylene ''~ (Eq. 2.8-2.9). [cat]

_

9 - H2 "-

••.

[Cat] - H2

,

I~

(2.8)

[~

(2.9)

The first method is a further step of the previously mentioned catalytic dehydrogenation of cyclopentane to cyclopentene (Eq. 2.10)

44

[Cat]

[Cat]

(2.10)

but, on the other hand, the catalytic dehydrogenation of cyclopentane could be conducted, under rigorous conditions, directly to the selective formation of cyclopentadiene (Eq. 2.11).

[Cat]

(2.11)

The second method starting from pyperilene involves also two steps, occurring with the intermediate formation of eyclopentene but, under the conditions employed, cyclopentene is not separated and the reaction is conducted to eyclopentadiene (Eq. 2.12).

C

[Cat] ~ )

[Cat]

-.2

(2.12)

The monomer cyelopentadiene is stable only by -80~ Over this temperature dicyclopentadiene forms by dimerization reaction. Because of the easy dimerizafion, fresh distilled cyclopentadiene is used. Cydohexene and substituted cydohexene. There are several techni~ proc~ures for the synthesis of cyelohexene and some of its substituted derivatives which can be found in the literature. ~ ' ~ Thus, cyclohexene can be manufactured by (i) catalytic dehydration of cyclohexanol 1~2 at 300400~ (ii) dehydrocldorination of ehlorocyclohexane on alumina-silica at 130-140~ (iii) deamination of cyclohexylamine on heating over several metal phosphates as catalysts, (iv) isomerization of cyelohexane to methylcyclopentane on the Friedel-Crafls catalysts with subsequent dehydrogenation over Cr203 to methyleyelopentene and further i~merization on AICI~-tCI to eyelohexene, t~4"~6 (v) dehydrogenation of eyelohexane on sulphur at 520~ and (vi) eycloaddition of ethylene and butadiene at temperatures of 150 to 350~ and 100 to 150 atm when 4vinylcyclohexene forms as a side-product. ~7 4-Vinylcyclohexene is produced n~nly by catalytic dimerization of but~ene in liquid phase over

45

Cu- or Cr-naph~enate at 163~ and high presmre, in gas phase over SiC at 425~ and 14 atm or over Ni at 400-500~ or by photodimerization with Hg-light at low pressure l is (Eq. 2.13).

+

\ / /

---.

(2.13)

By this reaction, 4-vinytcyclohexene is formed also as a side-product in the commercial installations for the manufacture of cyclododecatnene. C ~ d o h e ~ d i ~ e . 1,342ydohex~iene can be prepared m high yield from cyclohexene in two steps ~9"~2~(Eq. 2.14).

0

(CH3)3COCl 0- - _ . i ~ . 1177%

CsI"IsN(CH3)2; , . . ~081

C;

..._

(2.14)

n Bow,

The chlorination is done in excess refluxing cyclohexene with ten-butyl hypochlorite and d i ~ y l peroxide as a catalyst. The second step is carried out at a temperature such that cyclohexadiene distills as formed. On the other hand, 1,4-cyclohexadiene is readily available by the catalytic hydrogenation of benezene (F-xl. 2.15).

+H2 0

(2.15)

Cycloheptene and cydoheptadiene. Cycloheptene is obtained by the general procedure by dehydration of cycloheptanol under the influence of with [3-naphthylsulphonic acid121 (Eq. 2.1 6)

P~loH7S03 H 1180%

=

~

(2.16)

46 On applying the above two-step proc~ure used for cyclohexadiene manufacture, cycloheptene can be conveniently converted to 1,3cyclohe~adiene (Fxl. 2.17)

~P'~>(CH3)3C ,OCL i/C> CeHs~CH3)2 ~ C C

(2.17)

By a different procedure involving r i n g - ~ a r g ~ t of a copper intermediate, 1,3,5-cycloheptatriene can be prepared from benzene and diazomethane ~zz as shown in Eq. 2 18 9

(~ CH2N2 r C u BC~~~)uB r

.

-CuBr=_ C~

(2.18)

Other methods ~z3 imply pyrolysis of 7,7-dichloronorcarane at 500~ to 1,3,5-eycloheptatriene (yield 57%) and toluene ~~ or heating over CaO at 444~ to 1,3,5-cycloheptatriene (yield 63%) without toluene ~23b(Eq. 2.19).

CH3

(2.19) C a O

_ .._

A.4A.~ Cyclooctene and cydooctadiene. Cyclooctene, TM an important monomer for polyoctenamer production, can be prepared by the general methods employed for cycloolefin synthesis such as dehydration of cyclooctanol, dehydrochlorination of cyclooctyl chloride, dehydrogenation of cyclooctane and halogen elimination reactions of dihalides of cyclooctane. Of these methods, the most convenient procedure seems to be cyclooctadiene hydrogenation in the presence of specific catalysts as will be shown below. Cyclooctadiene is formed by cyclodimerization reaction of butadiene under the action of nickel catalysts ~2s'~ (Eq. 2.20).

47 ~

+ ~

[Ni]=

0

(2.20)

This reaction occurs in the synthesis of cyclododecatriene using nickel complexes. Ir7 When donor ligands, e.g. phosphites, have been used, the synthesis is directed toward cyclooctadiene formation and this process is the basis for the commercial production of cyclooctadiene. V'mylcyclohexene, a coproduct of butadiene dimerizafion, acts as a molecular weight regulator in further polymerization reactions and should be removed by fractional distillation. Partial catalytic hydrogenation of cyclooctadiene affords cyclooctene in high yield (Eq. 2.21). (2.21)

[Cat]

Cydooe~tetraene. The most straightforward way to prepare cyclooctatetraene is tetramerization of acetylene by the Reppe proceduremZS (Eq. 2.22).

1It + tit

~ ~

(2.22) .

.

.

.

The reaction occurs readily in high yield under the action of nickel cyanide at temperatures between 60~ and 70~ and pressure of 20 arm. Cydononene and eydononadiene. Cyclononene and cyclononadiene can be prepared on small scale amount by means of the general methods used for cycloalkene synthesis. Thus, cyclononene is prepared by elimination reactions from the corresponding cyclic alcohols, halides and dilmlides ff.q. 2.23-2.25). OH (2.23)

-HX ~

(2.24)

48

X -2X ..--- ~

(2.25)

1,3-Cyclononadiene is prepared from cyclononene via chlorination and dehydrochlorination, by an analogous way to 1,3-cyclohexadiene t~9"~2~(Eq. 2.26-2.27).

{~

(CH3)3COCI.~ .- p j ~

(2.26)

C

C6HsN(CH3)2-~ [ ~ ,

(2.27)

C Cyclodecene. This monomer can be conveniently obtained from cyclodecanol by dehydration with common dehydrating agents, e.g., P2Os (Eq. 2.28) OH

~

-H20. ~

(2.28)

Cydodecadiene. Cyclodecadiene is commercially produced by cyclo-cx~ trimerization of two moles of butadiene with one mole of ethylene t29 (Eq. 2.29).

( . )

[Cat]

>

~

(2.29)

Cydododecene and cydododecadienr The main source of cyclododecene production is by the selective hydrogenation of cyclododecatriene, a commercial product obtained by cyclotrimefization of butadiene 125'126'13~(Eq. 2.30).

(gao)

49

C y c l o d o d ~ e n e is commercially produced by c y c l ~ l i g o m ~ o n two moles ofbutadiene with two moles of ethylene (Eq. 2.31).

+

---

,C

of

(2.31)

Cydododecatriene~ Cyclotrim~tion of butadiene to c y c l o d o d ~ e n e occurs conveniently under the influence of three camdytic systemslU'l~: (a) titanium tetrachloride/ethylaluminium sesquichlorie, Co) "nacked nickel" and (c) chromyl chloride/triethylaluminium. (Eq. 2.32).

(2.32)

)

Four stereoisomers can arise, i.e., all-cis-, cis, trans, trans-, cis, cis, trans-,

all-trans-cyclododecatriene, the amount of which depends essentially on the catalytic system and reaction conditions (Scheme 2.34).

0_0 all-cis

CO cts, trans, trans

cis, cis, trans

all-trans

Schen~ 2.34

50 The ratio of the stereoisomers can be altered by varying the reaction temperature, pressure and nature of the catalyst. With TiCI4/Et3AI2CI3 as the catalyst, the main reaction product is cis, trans, trwts-cyclododecatriene. "blacked" Ni will form t r ~ , t r ~ s , tr~ms-cyclododecatriene as the main product while the system CrOCl2~hAl will produce c~z 60~ trans, trans, trans- and 40% cis, trans, trans-cyclododecatriene. The technical product, commercialized by Htils AG, Shell and Du Pont, 124'130with overall production of 40.000-45.000 to/year, is obtained with over 90% yield in installation presented schematically in Figure 2.2. Cyclooctadiene (COD) and vinylcyclohexene (VCH) are formed as side-products by accompanying cyclodimerization reactions of butadiene in the presence of the catalytic system. (Eq. 2.33).

[Cat] (2.33)

As Figure 2.2 illustrates, the initial butadiene is purified in a first column then oligomerized in the reactor under the action of the catalyst. VCH COD

Solvent

CDT

NaOH

Catalyst

Higher comp.

Butadiene

Figure 2.2. Production of c y c l ~ e (CDT) by butadiene cyclccximerization(side-products:cyclooctadime (COD) and vinylcyclohexene (VCH)) (Installation: l-Drying, 2-Reactor, 3-Catalyst l ~ i t i o n , 4-Solvent Recovery, 5-Separation Colunm, 6-Distillation Column)m

51 After monomer conversion, the catalyst is destroyed with aqueous NaOH solution and the organic phase is separated in the following three colunms: first, solvent recovery, second, separation of by-products, vinylcyclohexene and cyclooctadiene and third, distillation of cyclododecatriene. Selective hydrogenation of c y c l o d o d ~ e n e forms c y c l o d o d ~ e . This compound is an important intermediate in the manufacture of nylon-12 via the cyclododecane-lauryl lactam route. 2.5.2. Synthesis of Bicydic and Polycydic Olefins Norbornene and substituted norbornene. Norbomene and a wide range of substituted norbomenes are made directly by the Diels-Alder condensation of cyclopentadiene with ethylet~ or substituted ethylene. 131"13s Under high pressure and with a large excess of ethylene, good yields in norbomene are obtain~ from cyclopentadiene t~'13= (Eq. 2.34).

Q

=-

(2.34)

Substituted olef~ react easily with cyclopentadiene but the yields are largely dependent on the n a t u r e and bulkiness of the attached substituents 139q41(Eq. 2.3 5).

Q

(2.35)

Also, substituted cyclopentadiene takes part in reactions with olefins to produce norbomenes bearing multiple substituents in various positions ~42 (Eq. 2.36).

A large number of substituted norbornenes have been prepared by this versatile route. For instance, Alder and Ache ~42 prepared l-methyl-and

52 2-methylnorbomene by reaction of methylcyclopentadiene with ethylene (Eq. 2.37-2.38).

9~

(2.37)

(2.38) 2-Methylenenorbomane has been formed as a by-product in this reaction (Eq. 2.39). +

=

(2.39)

Starting from ethyl- or isopropylcyclopentadiene and ethylene, lethyl- and 2-ethylnorbomene as well as l-isopropyl- and 2isopropylnorbomene have been obtained by this reaction way t43 (Scheme 2.35).

Scheme 2.35 2-Ethylidene- and 2-isopropylidenenorbornane resulted also as by-products under these reaction conditions (Scheme 2.36).

Scheme 2.36

53 Special procedures have been applied for the manufacture of some substituted norbomene derivatives. Thus, J.D. Roberts et al. TM prepared 7methylnorbornene by the thermal reaction of 7-bromo-7-methylnorbomene with tributyltin hydride (Eq. 2.40). H

BaSaH .~

+

(2.40)

Starting from 1,3-cyclohexadiene, 7-bromo-7-methylnorbomene was obtained by debromination and rearrangement of the intermediate 7,7dibromo-bicyclo[4.1.0]hept-2-ene with methyllithium~45(Eq. 2.4 1).

~ ~ KOtBu~HB~[ ~ B I r CHIJ r

(2.41)

1,2-, 1,3- and 2,3-Dimethylnorbornene have been produced by Alder and Ache ~42 by cycloaddition reaction of dimethylcyclopentadiene with ethylene (Eq. 2.42-2.44).

(2.42)

(2.43) (2.44) Codimefization of cyclopentadiene with butadiene accompanied by thermal Cope rearrangement of the adduct gives two hydrocarbon monomers of

54 interest, 5-vinylnorbomene and bicyclo[4.3.0]nona-3,7]diene TM (Eq. 2.45).

In a similar way, 5-cyclohexenylnorbornene can be prepared by condensation reaction of cyclopentadiene with vinylcyclohexene ~47 (Eq. 2.46).

/ ~

(2.46)

Ethylene bis(5-norbornene) will be easily prepared by the Diels-Alder reaction of cyclopentadiene with 1,5-hexadiene ~47(Eq. 2.47).

.O

(2.47)

Four aryl-substituted derivatives of norbornene have been obtained by EI-Saz~n and Feast ~48by more elaborated methods. For instance, endoand exo-5,6-benzonorborn-2-ene were prepared by two independent ways starting from two different disubstituted benzene derivatives (Eq. 2.482.49).

[~

CHBr2

N.,.

]

(2.48)

CHBr z

endo

O

- [ ~ ~

(2.49)

exD

On the other hand, exo- and endo-5,6-acenaphthonorbom-2-ene were obtained by Diels-Alder addition of acenaphthene with dicyclopentadiene (Eq. 2.50).

55 + O

=

(2.50) enclo + exo

All the synthetic routes gave isomer mixtures which were rather complex and the required pure monomers were to be obtained by standard, albeit tedious, preparative chromatographic techniques. Benzo- and substituted benzobarrelene, monomers for highly conductive polymers, have been synthesized by two-step procedures starting from benzene derivatives ~49'~5~(Eq. 2.51-2.52). CI

CI

C ~ 1 ~ CI BuLi

CI

C F ~ l "Cl C61"~-

I

Na

=

~

(2.51)

Ph

O

O

F

~

.~--R ~-R KOtBu .~ LiN(CHMez)z

(2.52)

A series of norbornene derivatives, available by Diels-Alder synthesis, were prepared by ShellTM to manufacture thermoset copolymers. Such a monomer, 5,8-methylene-5a, Sa-dihydrofluorene, was obtained by the diene synthesis from indene and a mole of cyclopentadiene (Eq. 2.53).

(2.53) Similar reaction of 1,4-divinylbenzene with two moles of cyclopentadiene gave rise to 1,4-dinorbomylbenzene (Eq. 2.54).

56 An interesting monomer for thermoset polymers, 1,4,4a,9,9a,10hexahydro-9,10(l',2')benzene- 1,4-methanoanthracene, obtained Shell by this procedure from dibenzobarrelene and cyclopentadiene~5~ (Eq. 2.5 5).

(2.5s)

Norbornadiene. Diels-Alder reaction of dicyclopentadiene with acetylene will produce efficiently norbornadiene, ~$2 a highly reactive and quite versatile monomer (Eq. 2.56).

1~

" III

"

~

/ ~

(2.56)

The reaction occurs readily with mono- and disubstituted acetylenes providing mono- and disubstituted norbornadienes, ~53 respectively (Eq. 2.57-2.58).

I~

+ Ill

= ~

(2.57)

i~

, iII

~

(2.s8)

When substituted cyclopentadienes are employed as dienophile, 7substituted norbornadienes can be readily prepared by this method TM (Eq. 2.59).

C>- + III

~

(2.59)

57

Benzenorbornadiene and higher aromatic homologs. EI-Saafin and Feast ma prepared benzonorbomadiene by trapping benzyne with cyclopentadiene in a Dials-Alder process. The benzyne was generated from ~~lic and in the reaction with ~nyl nitrite (Eq. 2.60).

(z6o) c(x~

cooe

By a similar procedure, Feast and Shahada.155 prepared 2,3naphthonorbomadiene and 2,3-anthracenonorbomadiene reacting cyclopentadiene or dimethylenenorbomene with the reaoive acetylenic intermediates obtained from benzene or naphthalene derivatives. For 2,3naphthonorbornadienr two independent routes have been applied tl~ first involving cyclopentadiene addition with the acctylenic intermediate from naphthalene (F-.~l.2.61).

(2.61)

while the second addition of dimethylenenorbomene to the reactive intermediate benzyne obtained by diazotization of anthranilic acid (Eq. 2.62).

==

[ox]

(2.62)

58 Synthesis of 2,3-anthracenonorbomadiene occurred analogously from the corresponding naphthalyne obtained from 3-amino-2-naphthoic acid via ~ene d i a z . o n i u m - 2 ~ x y l ~ e as illustrated below (Eq. 2.63).

(2.e3)

This procedure can be easily applied to higher arene homologs bearing norbomene end groups. Trit-ydononene. Tricyclononene or deltacyclene is readily available via cobalt-catalyzed [2+2+2] homo-Diels-Alder reaction of norbomadiene with acetylene ~s~(Eq. 2.64).

+ III Analogously, substituted deltacyclene bearing butyl, phenyl or trimethylsilyl groups have been prepared from norbomadiene and the corresponding substituted acetylenes (Eq. 2.65).

RIll

=

(2.es)

R R = B u , Ph, Me Si

Tricyclo [4.3.0. I z~]dec-3-ene or trimethylenenorbornene~ T rimethylenenorbomene can been prepared by two independent routes i.e. Diels-Alder condensation of cyclopentadiene with cyclopentene ~" or partial catalytic hydrogenation of dicyclopentadiene (Eq. 2.66-2.67).

59

O

9 C} H

~~~

.266.

~..~~

.26,.

The choice of the method depends essentially on the availability of the raw materials Tricydo[4.3.0.1Z~]deca-3,7-diene or dicyr This important monomer is recovered directly from refinery streams after thermal dimerization of cyclopentadiene (Eq. 2.68).

The crude product is unsatisfactory for polymerization due to the large amount of residual cyclopentadiene and other C5 dienes which can act as a catalyst poisons. As the normal dicyclopentadiene contains two stereoisomers, endo and e x o (Eq. 2.69)

(2.69) exo

endo

the separation of these two stereoisomers can be carried out by special techniques. Tricydo[4.4.0.1Z~]undeca-3-ene. This hydrocarbon and the higher polycyclic homologs can be easily prepared by Diels-Alder reaction of cyclopentadiene with cyclohexene 157(Eq. 2.70).

O

. O

60 When two or more moles of cyclopentadiene are employed, polycycilc olefins having cyclohexane end can be produced (Scheme 2.37).

Scheme 2.37 Tricyclo[4.4.0.12,s] undeca-3,8~iene. Tricyclo[4.4.0.12"5]undecat-3,8-diene is readily available by the condensation reaction of cyclopentadiene with

1,4-cyclohexadiene (Eq. 2.71).

O

=

(2.71)

With two or more moles of cyclopentadiene, two series of polycyclic olefins will arise, this depending on which of the double bonds will take part in the diene synthesis (Scheme 2.3 8).

Scheme 2.38 Tricyclo[4.5.0.12"Sldodeca-3-ene. Diels-Alder reaction of cyclopentadiene with cycloheptene will form easily tricyclo[4.5.0.12'5]dodeca-3-ene ~57 (Eq. 2.72).

Higher homologs will be produced by further Diels-Alder reaction of trieyclo[4.5.0.12"5]dodeca-3-ene with r (Eq. 2.73).

61 Tricydol4.6.0.1Z~tridec~3-ene. This hydrocarbon is readily available by the Diels-Alder reaction of cyclooctene with dicyclopentadiene or by partial hydrogenation of tricyclo[4.6.0.1 z'S]trideca-3,9-diene (Eq. 2.74). ,,

O + ()

"'"

Further reactions of tricyclo[4.6.0.1 ~S]trideca-3-ene with dicyclopentadiene will form higher polycyclic monomers (Eq. 2.75).

>o ~

. ) (2.75)

Tricydol4.6.0.1z~ltridec~-3,9-diene. 1,5-Cyclooctadiene and cyclopentadiene will react readily to produce tricyclo[4.6.0, l Z'S]trideca-3,9diene (Eq. 2.76).

O+ ( )

(2.76)

Two series of higher polycyclic homologs will arise by further reaction of one of the t w o double bonds of tricyclo[4.6.0.12"S]trideca-3,9-diene with cyclopentadiene (Scheme 2.39).

Schen~ 2.39 Tetracyclo [4.4.0.1 ~s. 17't~ dodec-3-ene tetracyclo [4.4.0.1 ~s. 17't~ dodec-3-ene.

and substituted Tetracyclododecene or be easily prepared from

dimethanooctahydronaphthalene can dicyclopentadiene and ethylene. ~ss In a first step, dicyclopcntadicne is cracked at high temperature to make two equivalents of cyclopentadiene.

62 In a second step, addition of ethylene to cyclopentadiene yields norbomene. The norbomene acts as a dienophile in a third step for the liberated cyclopentadiene, resulting in a concerted [4+2] cycloaddition (Eq. 2.77-

2.78).

(l)

C + i,

=.

2. [ ~

(2.77)

3_C>

(2.78)

Addition of cyclopentadiene to norbomene can occur in four distinct ways to yield four distinct stereoisomers: endo, exo-, exo, exo-, endo, endoand exo, endo-tetracyclododecene (Scheme 2.40).

endo, exo

exv, exo

endo,endo

exo, endo

Scheme 2.40 Soloway Is9 showed by a synthetic procedure that the major isomeric component from the cycloaddition reaction of norbornene to cyclopentadiene was the endo, exo-tetracyclododecene. This result has been recently confirmed by an elegant method by Benedikt et al. ~6o using highresolution NMR spectroscopy. By a similar route substituted tetracyclododecene can be prepared using monosubstituted or disubstituted clienophiles in the Diels-Alder reactions with cyclopentadiene (F_,q. 2.79-2.80).

63

i~ + ( ~

I~

(2.80)

Diels-Alder reaction of norbomadiene with cyclopentadiene gives tetracyclo[4.4.0. I z'5.17'~~ ~6~(Eq. 2.81).

I~ + / ~

~ ~

The same product can be obtained in a two-step cyclopentadiene and acetylene (Eq. 2.82).

(2.81) process from

By a similar way to tetracyclododecene, four distinct stereoisomers: endo, exo..exo, exo-, endo, endo- and exo, endo-tetracyclododecadiene occur (Scheme 2.41 ).

e n d o , exo

exo, exo

endo, endo

Scheme 2.41

exo, e n d o

64 Substituted tetracyclo[4.4.0.12"~,l~'t~ can be conveniently prepared in one step by the Diels-Alder reaction of dicyclopentadiene with substituted norbomadienes or in a two-step process from cyclopentadiene and substituted acetylenes (Eq. 2.83-2.84).

E~

+ III ~

~

(2.83)

E~

+ iii ~

~

(2.84)

I

The presence of substitutent at one of the carbon-carbon double bonds of the monomer will prevent this bond from cross-linking reactions during polymerization but will give the possibility to further functionlize the polymer by certain chemical reactions. Pentacyclo[ 10.2.1.0xlm.0~'t=]pentadeca-2-ene. This monomer can be easily prepared from octahydronaphthalene and cyclopentadiene by the DielsAlder reaction (Eq. 2.8 5).

=

~

(2.85)

Pentacyclo[10.2.1.1xs.02"tt.0m'9]hexadeca-6-ene, When starting from tricyclo[4.4.0, l~]undeca-3,8-diene or methyleneoctahydronaphthalene and cyclopentadiene, pentacyclo[ 10.2.1.15'8.02"tt.04'9]hexadeca-6-ene is obtained (Eq. 2.86).

65 Hexacydoll0.2.1.13'tS.lS~.0z'tt.0~ Diels-Alder reaction of tetracydo[4.4.0.12,5.17,10]d~e~-3-ene with dicyclol~m~ene gives hexacyclo[ 10.2.1.13'1~ I s'S.o~lt.O4~hept~lee~-6-ene (F~. 2.$7).

(2.87) Hepts~ddo [ 14.2.1. I s,t2.1 ~'ts.0z'ts.0~ t3,0s'ts]doeicotm-i-ene, dicyclopentadiene with pentacyclo[ 10.2.1.1 s,s.02,11.04#]hexader reacted hepta~r 14.2.1.1 s,t2.17"l~ obtained (Eq. 2.88).

When is will be

(2.88) Octacyclo[ 14.2.1. l~'t4. I s't2.17'ts.0z'ts.04't3.06'tS]doeicosa-g-ene. Further reaction of hexacyclo[10.2.1.13,t~ lS'S.02'tt.04a]heptade~-6-ene with dicyclopentadiene gives a new norbomen~like monomer octacyclo[ 14.2.1.13,t4. I s,t2.17't~ (Eq. 2.89).

Other multieydk norbornene-like monomers. The Diels-Alder reaction of cyclopentadiene with a variety of cycloolefins will produce a large number of norbomene-like monomers having one or more norbornene moieties in the molecule. In this way, reaction of cyclopentadiene with cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene and higher cycloolefins will provide a full series of tricyclic monomers containing one norbomene moiety in the molecule (Eq. 290)

C +C(CH2)n

(2.90)

66 Reaction of various cyclic dienes and polyenes with cyclopentadiene e.g. cyclohexadiene, cyclooctadiene, cyclooctatetraene, cyclododecatriene, etc. will form penta- and multicyclic olefin~ containing two and more norbornene moieties as a function of the number of double bonds of the reacting cyclooletin (Eq. 2.91).

+

(2.91)

+

(c

(CH2)rr

Examples for cyclohexadiene, cyclooctadiene, cyclooctatetraene and cyclododec~triene are illustrated in Eq. 2.92 - 2.95.

(2.92)

(2.93)

(2.94)

O.,C

(2.95)

Further Diels-Alder reactions of these monomers with cyclopentadiene at any available double bond of the first formed molecule will produce higher homologs of interest for the vinyl polymerization or ring-ol~ning metathesis polymerization (Scheme 2.42).

67

Schemo 2.42

A special class of interesting norbomen~like monomers is formed from the higher oligomers of cyclopentadiene e.g., tricyclopentadiene, tetracyclopentadiene, pentacyclopentadiene, etc. Thus, starting from dicyclopentadiene as dienophile in the reaction with cyclopentadiene two types of tricyclopentadiene monomers can arise: (i) first, by addition of the more reactive norbornene double bond to cyclopentadiene will form the cyclopentene ring terminated monomer (F-x1.2.96)

-

(296)

and (ii) second, by addition of the least reaofive cyclopentene double bond to cyclopentadiene will form the norbomene moiety terminated monomer (Eq. 2.97).

+

r

Similarly, tetra-, penta- and multicyclopentadiene monomers will be produced readily from cyclopentadiene by successive Diels-Alder reactions (Scheme 2.43).

68

Scheme 2.43

If the starting molecules is indene and cyclopentadiene is then reacted successively, several l~lycyclic norbomene-like monomers l~ving the indane end group can be obtained ~62 (Eq. 2.98).

The synthesis of a fullerene monomer, the C6o derivative of norbornene, has been successfully effected in 43 % yield by Prato et al. ~63 by the reaction of quadricyclane with C60 hydrocarbon in toluene at 80~ (Eq. 2.99).

A (2.gg)

This highly strained monomer has been effectively employed in the metathesis copolymerization reaction with norbomene to produce high molecular weight polymers with interesting electronic and electrochemical properties.

69 2.5.3. Synthesis of Functionalized Cydoolefins A large number of substituted cycloolefins containing a variety of functional groups can be prepared either by conventional or specific methods. 2.5.3.1. Halogen-Containing Monomers Fluorinated compounds. Fluorinated bicyclo[2.2, l]heptenes were prepared by Feast and Wilson 's4 via Diels-Alder reaction of fluorinated alkenes as &enoplfiles, i.e., 3,3,3-trifluoropropene, perfluoropropene, perfluoro-2-butene and 2,3-dichlorohexafluorobut-2-ene, with cyclopentadiene (Eq. 2.100-2.103).

[~

+

CF3

CHCF3 II CH2

-'~

(2.100)

H F [~

[~

.

+

CF2 II CFCF3

CFGF3 II CFCF 3

=

(2.101) CF3 CF3

.

~

(2.102) CF3

[~

+

CClCF3 II CClCF3

CF3 ..-

CI

(2.103)

CF3 Fluorinated bicyclo[2.2.1]-hepta-2,5-dienes have been similarly prepared by the same authors through the reaction of fluorinated alkynes as dienophiles, e.g., hexafluorobut-2-yne and 3,3,3-trifluorobutyne, with cyclopentadiene (Eq. 2.104-2.105).

70

[~

CCF3 +

~

III

CCH3

[~

(2.104)

CH3 ~

CCF3 III CCF3

+

cF3

.~

CF3

=

(2.105)

CF3

Reaction conditions and yields obtained in the synthesis of some fluorinated bicyclo[2.2, l]heptenes and bicyclo[2.2.1 ]-hepta-2,5-dienes are presented in Table 2.2. Table 2.2. Synthesis of fluorinated bicyclo[2.2, l]heptenes -2t5-dienes' Dienophile Reaction Ten~rature time~ hr ~ CF3CF--CFz 72 160 CF3CF=CFCF3 24 100 CF3CH---CH2 72 160 CF3CCI=CCICF3 72 160 100 CF3C=C=CF3 24 155 CF3C~CH 48

and

'Data~ n reference~

Yield % 85 90 65 35 90 82

'

Diels-Alder addition of fulvene and substituted fulvenes to hexafluorobut-2-yne as dienophile gives rise to a new series of fluorinated norbomadienes~S (Eq. 2.106-2.107).

[ ~

+

i

F3

CF3 CF3

CFa

~

F3 CF3

(2.106)

71 When perfluorinated cyclobutene and cyclopentene were used as dienophiles in Diels-Alder reaction with cyclopentadiene, highly fluorinated norl~mene derivatives have been obtained ~ (Fxi. 2.108-2.109). 9 F

IF.

(2.108)

F

F•

[~+

F

F

---~

(2.109) F dienophile,

Similarly, with N - C 6 F s - m a l ~ d r as cyclo~tadiene produced a new fluorinated norbomenederivativesuitablefor ring-opening metathesis polymerization '6v (Eq. 2.110). 0

~~)

N-CeF5

4-

0

=O N'--CeF5

(2.110)

By the reaction of tetrafluorobenzyne with cyclopentadiene or dimethylfulvene, fluorinated arenenorbomadienes can be obtained 16s'169 (Eq.

2.111-2.112).

.I

F F

(2.111)

F F

-1 F

tF F F

(2.112)

72 The reaction of 2,3-dimethylenebicyclo[2.2.1 ]hep-5-ene with a perfluorobut-2-yne provided bis(trifluoromethyl)methanotetrahydronaphthalene (Eq. 2.113). CF3

(2.113) CF3

3

Further dehydrogenation of bis(trifluoromethyl)methanotetrahydronaphthalene led to 9,10bis(trifluoromethyl)benzobicyclo[2.2.1 ]hepta-2,5-diene ~7o(Eq. 2.114).

//

CF 3

H =

CF3

3

(2.114)

3

By an alternate route, the bridgehead isopropylidene derivative of 9,10-bis(trifluoromethyl)benzobicyclo[2.2.1 ]hepta-2,5-diene could be prepared from dimethylfulvene and 4,5-bis(trifluoromethyl)benzyne ~'~ (Eq. 2.1 15).

"cFa

.=

r'-~",,,~CF3 (2.115)

CF3

~CF3

The monomer 7,8-bis(trifluorome~yl)tricyclo[4.2.2.02"5]deca-3,7,9-triene, used by Edwards and Feast ~7~ for the preparation of polyacetylene precursor polymers has been readily synthesiz~ in 80 % yield by the thermal reaction between hexafluorobut-2-yne and cyclooctatetraene'n'~n at 120~ (Eq. 2.116).

F3C

(2.116)

+ -

#

CF 3

F3C,)

73 Another fluorinated monomer, used in the "Durham" precursor route for polyacetylene synthesis, 3,6-bis(trifluoromethyl) pentacyclo [6.2.0.02'4.03"6.0s'~]dec-9-ene, can be conveniently prepared by the photoisomerization reaction of 7,8bis(trifluoromethyl)tricyclo[4.2.2.0~'S]deca-3,7,9-triene~7~ (Eq. 2.117).

F3C\ . . ~

F3C~ (2.117)

Chlorinated compounds. A wide range of chlorinated monomers with the potential of manufacturing flame retardant polymers have been prepared by chlorinating the cycloolefms and subsequently reacting these chlorinated products with new monomers. Cycloolefins of the monoene, diene or polyene type provide chlorinated monomers by direct chlorination or hydrochlorination, but the reaction has generally a low s r 175 Chlorinated cyclopropene can be prepared by the general methods used for this type of compounds such as dehydrochlorination reaction of dichlorocyclopropane in the presence of bases, leading to lchlorocyclopropene (Eq. 2.118).

+

HCI

(2.118)

or direct chlorination of cyclopropene in the presence of specific initiators, with formation of 3-chlorocyclopropene ~" (Eq. 2.119).

~> + CI2 ~

~-CI

+ HCI

(2.119)

Chlorinated cyclobutene can be manufactured by similar methods from cyclobutene by the selective chlorination in the allylic position or from dichlorocyclobutane by mild dehydrochlorination (Eq. 2. 120-2.121). /CI

§

oh

il !

+

NO,

(2 2o)

74 /CI

! !

\

"~

[

I

J

CI +

HCI

(2.121)

cI

Using the above procedures, l-cldorocyclopentene can be obtained from 1,2-dichlorocyclopentane through dehydrochlorination while 3chlorocyclopentene from cyclopentene via direct chlorination of cyclopentene (F4.2.122-2.123). Cl +

HCI

(2.122)

Cl

On the other hand, chlorinated bicyclic and polycyclic olefins can be prepared by several more specific methods. Thus, reaction of norbomadiene with dichlorocarbene, generated from chloroform under the action of aqueous alkali solution in the presence of a phase transfer catalyst, provides exo-3,4-dichlorobicyclo[3.2.1]octa-2,6-diene as the main product m76 (Eq. 2.124).

(2.124) CI

Reaction of this compound with lithium aluminium hydride in dry ethyl ether produced 3-chlorobicyclo[3.2.1]octa-2,6-diene in high yield (Eq. 2.125).

C~CI LiAIH_._

(2.125)

I Tetrachlorocyclopropene, prepared from trichloroethylene and dichlorocarbene with subsequent dehydrochlorination, ~" reacts readily I

75 with excess cyclopentadiene at room temperature to form 2,3,4,4tetrachlorobicyclo[3.2.1 ]octa-2,6~ene ~76(Eq. 2.126).

+

C

I

25oc c,

(2.126)

cs

C Reaction of tetrachlorocyclopropene with 6,6-dimethylfidvene under more severe conditions (reflux temperature for 24 hr) gives rise to 2,3,4,4tetrachloro-8-isopropylidenebicyclo[3.2, l]octa-2,6-diene~*S (Eq. 2.127). CI

C

CI

24h

+

CI (2 127)

c

I

cch

cI

"

Diels-Alder reaction of cis-3,4-dichlorocyclobutenem with dicyclopentadiene yields as the main product endo-cmti-3,4dicNorotricyclo[4.2.1.0~]non-7-ene of the fmH" possible isomers, endo, anti-, a~o, syn-, exo, anti-exo, syn-isomers 1~6(Eq. 2.128).

I

~ ~ +

CI

endo-enli

exo-syn

CI endo4yn

(2.128)

"~CI cl$ exo4ntl

Chlorinated cyclopentadiene reacts with a wide range of dienophiles to produce chlorinated norbomene derivatives of high interest as monomers for ring-opening p o l y m ~ o n reactions. Thus, the Diels-Alder adduct of 5,5-dichlorocyclopentadiene with acetylene will readily produce 7,7dichloronorbomadiene (Eq. 2.129).

76 C

cl

CI

+ III

=

(2.129)

Reaction of dichlorocyclopentadiene with cyclooctadiene will form the corresponding chlorinated tricyclic and tetracyclic hydrocarbons (Eq. 2.130-2.131). C

+ I

( )

CI

~

(2.130)

8O

c c, (2.131)

Similar reactions of hexachlorocyclopentadiene (obtained by the exhaustive chlorination of cyclopentadiene) with various cyclodienes, including cyclooctadiene and norbomadiene, give rise to potential monomers for flame retardant polymers. With an excess of cyclooctadiene, the 11 Diels-Alder adduct of perchlorocyclopentadiene with cyclooctadiene was prepared in high yield~79(Eq. 2.132).

cK~Cl CI

CI

(2.132)

i,...._

CI

C

This monomer is a crystalline product and is recovered by precipitation rather than by distillation. Elastomers derived from this compound have been explored in some detail. Analogously, the Diels-Alder reaction of perchlorocyclopentadiene with norbomadiene will form the 1"1 adduct, Aldrin, a potential monomer for flame retardant polymers ~s~(Eq. 2.133).

77

cK/cl CI Cl

O

CI CI Cl

C l ~ ~

+

(2 133)

Other cycloolefins can react in a similar way with chlorinated cyclopentadienes to produce a variety of chlorinated bicyclic and polycyclic monomers of interest for specialty polymers production. Isodrin~S~ obtained from cyclopentadiene and 1,2,3,7,7pentachloronorbomadiene, is another attractive monomer for highly chlorinated polymers (Eq. 2.134).

<3

CI

CI lb..-

(2.134)

I

I 2.5.3.2. Oxygen-Containing Monomen

Alcohoh. 5-Hydroxybicyclo[2.2.1]hept-2-ene was prepared from 5acetoxybicyclo[2.2.1]hept-2-cne by hydrolysis with sodium hydroxide in water at reflux for 8 hours '=~ (Eq. 2.135).

~~7,/

OAc

H O ~~~7,/OH , -'~ NaOH

(2.135)

On the other hand, 5-hydroxymethylbicyclo[2.2.1]hept-2-ene ~'~ could be obtained from 5-carbox~icyclo[2.2.1 ]hept-2-ene by reduction with LiAIH4 (Eq. 2.136).

LiAIH4

(2.136)

Et20 COON

20H

78 A dialcohol, 2,3-dihydroxybicyclo[2.2.1]hept-5-ene, was manufactured from bicyclo[2.2.1 ]h~t-2,5--diene by the selective oxidation of one double bond with OsOJN-methylmorpholine N-oxide ~z (Eq. 2.137).

o,o, oOH

(2.137)

Ketones. The 11 Diels-Alder adduct of cyclopentadiene with dichlorovinylene carbonate hydrolyzed readily in aqueous 1,4-dioxane to yield the ~-diketone, bicydo[2.2, l]hept-2-ene-2,3-dione ~ (F~. 2.138).

CI

0 (2.138)

0 0

This monomer has been used in metathesis copolymerization reactions with norbomene. Related monomers employed in similar copolymerization reactions were 3,3-dimethowbicyclo[2.2.1]hept-5~2-~ne and exo-3chlorobicyclo[2.2.1 ]hept-5-ene-2-one (Scheme 2.44).

.OMe Me

Scheme 2.44 Ethers.

5-Methoxymethylbicyclo[2.2.1]hept-2-ene was obtained in two

steps starting from 5-~xybicyclo[2.2.1 ]hept-2-ene via 5-hydroxymethyl compound as an intermediate ~*~(Eq. 2.139).

Et20 COOH

2.Mel/Me2SO CH2OH

CH2OMe

79 Another norbomene ether, 7-methoxybicyclo[2.2. l]hept-2-ene, was prepared from the corresponding acetate by basic hydrolysis and subsequent conversion of the potassium salt with methyl iodide ~ (Eq. 2.140). e

KOH

CH31

(2.140)

7-tert-Butoxybicyclo[2.2.1]hepta-2,5-diene can be directly prepared from norbomadiene using readily available reagents lss (Eq. 2.141).

U (2.141) This compound may in turn be converted into the whole range of 7substituted derivatives of norbomadiene (Eq. 2.142). U

(2.142) where X is alkyl, phenyl, OR, CI and COOK. Carboxylic acids. Bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid was obtained by hydrolysis of the Diels-Alder adduct of cyclopentadiene with maleic anhydride in warm water (Eq. 2.143).

~~C

c Q~ O/O

~ c "---"~"

0 0H COOH

(2.1 4 3 )

Esters. Bicyclo[2.2.1]hcpt-5-en-2-yl acetate was prepared by the DielsAlder reaction of cyclopentadiene with vinyl acetate TM (Eq. 2.144).

~

*

L

(2.144) OCOCH3

COCH3

80 Both e ~ and exo-isomers are formed (75 % endo, 25% exo) which could be separated by distillation though a spinning band column at 45 mmHg. When acrylates and methacrylates are employed as dienophiles, 5carboalkoxy-bi~do[2.2.1 ]hept-2-ene can be produced (Eq. 2.145-2.146).

Q

+ ~

~

(2.145)

COOR

COOR (2.146)

Anhydrides, Both e x o and endo isomers of bicyclo[2.2.1 ]hept-5-cne-2,3dicarboxylic anhydride have been pre~ed by Diels-Alder reaction of dicyclopentadiene with maleic anhydride (Eq. 2.147).

C>

CO

+

co 0~0

/0 ~

(2.147)

CO Whereas endo isomer is essentially inert in the presence of classical metathesis catalysts, the exo isomer undergoes smooth metathesis homopolymerization and copolymerization. 2,3-Dichlorobicyclo[2.2. l]hept-5-ene-2,3-
+ Cl~l cON0

Cl/Nco/

=

C JCOx

Cl

o/O

(2.148)

Shahada has shown that the endo stereoisomer readily polymerizes in the presence of metathesis catalysts.

81 Carbonate~ Norbom-5-ene-2,3-diyl bis(methyl carbonate) was prepared from norbom-5-ene-2,3-diol and methyl chloroformate at room temperature in the presence of pyridine (Eq. 2.149).

+ 2 HCOOMo ~

[ ~ OCOOMo ~OCOOMo

(2.149)

3a, Ta-Dichloro-3a,4,7,Ta-tetrahydro-4,7-methano..l,3- benzodioxol-2-one, another cyclic norbomene carbonate, was prepared by thermal Diels-Alder condensation of 1"1 dichlorovinylene carbonate and cyclopentadiene~n(Eq. 2.150).

Q§

c C

o,

o,C~

The endo isomer has been employed by Feast and Harper m in the ringopening polymerization with classicalmetathesis catalysts WCI6/Sn(CH3)4. 3a,9a-Dichloro-3 a,4,4a,5,8,8a,9,9a-octahydro-4,9: 5,8- dimethanonaphtho[2.3--d]-l,3-dioxol-2--one was obt~ed by Diels-Alder reaction of 1:2-dichlorovinylene carbonate with cyclopentadiene (Eq. 2.151).

ck o\ +clio c~

CI

\

(2.151) O

Again, the endo,endo isomer has been analogously used by Feast and Harper ts3 in the ring-opening polymerization with the metathesis catalyst WCts/Sn(CH3),. 2.5.3.3. Sulphur-Containing Monomers

Bicyclo[2.2.1]hept-5-cne-2,3-di(S-methyl dithiocarbonate) was manufactured staring from bicyclo[2.2.1 ]hept-5-2,3-diol reacted in a first step with caubon disulphide and then iodomethane ~95(Eq. 2.152-2.153).

82

OHH

SII I ~ /O-~C-S H ~O-(~-S H

CS2 ._ DMSO "-

S

(2.152)

S

O--(~-SH

CH31

.._ fi,,,[~,/O-~ -SCH3

NaOH

v

~,'--',.,,z.~ , .,,.. , O_,.~_SCH3 L, (2.153)

2.5.3.4. Nitrogen-Containing Monomers.

Nitriles. Diels-Alder reaction of cyclopentadiene with acrylonitrile produces readily bicyclo[2.2. ] ]hept-5-ene-2-nitrile i~mgs (F-xl. 2.154).

+

II,.

CN

_

(2.154)

CN When methacrylonitrile is employed in conjunction with cyclopentadiene, 2methyl-2-cyano-bicyclo[2.2.1 ]hept-2-ene will be formed (F_,q.2.155).

+

;L

CN

(2.155)

CN Amides. Reaction of acrylamide and N-substituted acrylamide with cyclopentadiene gives rise to norbornene derivatives bearing amide and Nsubstituted amide group ~99(Eq. 2.156-2.157).

"-

CONH2 r

CONHR

/~CONH

~~,,CONHR

2

(2.156)

(2.157)

83

Imides. Cycloaddition reaction of cyclopentadiene with m a l ~ d e bicyclo[2.2, l ]hept-5-ene-2,3-dicarboximide z~176 (Eq. 2.158).

CO

H

forms

(2.158)

Similar reaction of N-alkyl maleinimides with cyclopentadiene will produce N-substituted bicyclo[2.2,l]hept-5-ene-2,3-di~xi~deslZ~176176 (Eq. 2.159).

2.5.3.5. Boron-Containing Monomers.

(5-Cyclooctenyl)diethylborane has been prepared statlfi~ from cyclooctadiene and catecholborane. The intermediate borinated compound treated with diethylaluminium chloride led to the final product" (Eq.

2.160).

Et.AI~ ( ~-BEt (2.160)

0 "

Norbomenyl-9-borabicyclononane was produced by hydroborinating norbomadiene with 9-borabicyclononane (Eq. 2.161). B

+ /"~"1

B

(2.161)

The ~H NMR spectrmn of the monomer was found to be in agreement with the expected structure for the exo form. This hydrobofination reaction was very selective, occurring by cis addition from the less hindered side of the double bond of norbomadiene.

84 2.5.3.6. Silicon-Containing Monomers.

2-Trimethylsilylbicyclo[2.2.1]hept-5-ene can be readily available by Diels Alder reaction of cyclopentadiene with vinyltrimethylsilane7~ (Eq. 2.162).

C

+ IL ' SiMe3

=- ~_J~SiMe3

(2.162)

In case that allyltrimethylsilane is employed as dienophile instead of vinyltrimethylsil~e, 5-methyl(trimethylsilyl)bieyr will be produced 2~ (Eq. 2.163).

(2.163)

/~SiMe3

§ II

'~ilVle3 Diallyldimethylsilane will form two different silylated addition products as a function of the reaction conditions. With 1 equivalent of diallyldimethylsilane cyelopentadiene gives rise to 5methylene(allyldimethylsilyl)bicyclo[2.2.1 ]hept-2-ene whereas two equivalents of diallyldimethylsilane lead to bis(5methylenebicyclo[2.2.1 ]hept-2-ene)dimethylsilane 2~ (Eq. 2.164-2.165).

C

2

[~

---N S i / / N

+

+

--- \

__

/

Si

'

/ N

~--

(2.164)

/ \

I

2-Dimethylsilylbicyclo[2.2.1 ]hepta-2,5-diene has been prepared using Schlosser method by metallation of bicyclo[2.2.1]hepta-2,5-diene and further reaction of the metallated intermediate with dimethylchlorosilane z~ (Eq. 2.166).

85

tBuONa THFI-50~

U

HSiMe2C/ j ~ 20-250C

iMe2H

"-

(2.166)

2.5.3.7. Metal-Confining Monomers. At present a large number of metals have been introduc~ as component parts of polymefizable monomers. Of these, tin and germanium form a first group that give rise to monomers used for specialty polymers. Cyclooctenyltributyltin is thus formed from cycloctadiene and tributyltin hydride2~ (F,q. 2.167).

( )

+ Bu3SnH ~

(

~Sn

(2.167) Bu3

Similar reaction of norbornadiene with tributyltin hydride will produce 2tributyltinbicyclo[2.2.1]hept-5-ene (Eq. 2.168).

+

Bu3SnH

/ ~ S

nBu3

(2.168)

Analogously, the addition reaction of allyltrimethylgermanium with cyclopentadiene w i l l form a 5-substituted norbomene having trimethylgermanium attached at the side group ~~ ~ q . 2.169). I>,,, N / (29169) + Ge ~ Ge A series of substituted norbomenes containing Sn, Pb and Zn have been also prepared by Diels-Alder reaction of cyclopentadiene with the corresponding aza-metallacycles210-2 12(F,q. 2-170-2.172).

tBu

/tBu N!

"SnCI 2

Nk/tBu

N\/ ~u

(2.170)

86

SiMe

+

Pb

~

'

~

,SiMe3

~~"'""~NXpb

SiMe3

SiMe3

tBu

0

(2.171)

tBu

+ C

"-

1~'n "R

\R

(2.172)

\tBuXR

They were used for synthesis of the block copolymer films that are static cast from benzene and contain the organometallic reagent distributed in lamellar, cylindrical, or spherical microdomains. Substituted norbornenes derived from metallocenes of lead are easily available by Diels-Alder reaction. 2~3-zm4These lead metallocenes may contain one or more dienophiles able to react with one or more equivalents of cyclopentadiene (Eq. 2.173).

+

'm-"--"

~

~

(2.173)

The same derivative of lead, Pb(CpN)2, could be prepared in 85% yield from LiCp~ and PbCI2 as a pure endo compound 213 (Eq. 2.174).

2

PbCI2

THF ..=

+ 2 LiCl

(2.174)

85%

Li

Ferrocene and c o b a l t ~ e derivatives are suitable dienophiles which form Diels-Aldcr adducts with cyclopentadiene2~s (Eq. 2.175-2.176).

87 C02Me

Fo

~t~

+

=

,~~

(2.175)

v C02Me

Co

+

~

~

v

(2.176)

Palladium-containing monomers having norbomene moiety were prepared from palladium complexes and cyclopentadiene by the Diels-Alder route2~6. 2~7(Eq. 2.177).

"0

"

,2,77,

Polymer films with small palladium clusters (<100A) whose sizes and size distributions vary with the size of the metal-c~ntaining spherical microdomains.

2.5.3.8. Monomers for Side-Chain Liquid Crystalline Polymers A novel synthesis of a 5-substituted cis-cyclooctene, cis-[1 l-(4'cyanobiphenyl-4-yloxy)undecyl]r used as a monomer to obtain a side-chain liquid crystafime poly(l-octenylene), reported S t e ~ and coworkers 2~s (Eq. 2.178). (2.1711)

Several monosubsfituted norbornene derivatives bearing different methoxyand cyanobiphenyl groups as mesogenic entities have prepared Schrock and coworkers z~9.~ (Eq. 2.179-2.182).

88

.... K2~MF

=-~~~CH20(CH*~nO'~~~~

(2.179)

=- ~~~wCO2(CH2~f~~~~)Me (2.180)

HO(CH2~CN

.

.

.

.

.

Ne~a,'rHr

: ~Oz(CH2~CN

=- ~

(2.181)


_,_ .,~)r~

(2.182)

The norbomene derivatives used as monomers for the synthesis of laterally attached side-chain liquid crystalline polynorbomenes were prep~'ed by Pugh and ex~workers224~ by two different methods. The first method was applied to prepare monomers bearing mesogenic groups with hydrocarbon and fluorocarbon segments (Eq. 2.183-2.184).

,CH2Br

K2CO3 DMF

~

O __/CH20 H(CH2)nOQO~~( _

cH 2 ~ H (F_x].2.IB3)

89

~ f ~ ,CH2Br F(CF2)rn(CH 2 ~ O ~ C O-~__/~OC ~ O ( C O O

K2co31 &

H2)n(CF2)mF

DMF

OOH

CO I

F(CF2)m(CH2)nO~ C

~ ~ ,CH20 O--~,__/~--O(~~ O ( C O O

H2)n(Cg2)mF (Eq. 2.184)

The second method for the synthesis of monomers having mesogenic groups with oligosiloxane substituents (Eq. 2.185).

~, ~,

~~o~

CHl--~l--(O-~l)m---~CHz)rtO~O CHz CHz

(~

~ ~ H~

Ha

(CHz)ct---( F,--O)m-- I,~CHI CHz Hz

CHzCiz

OCI

~xo c

,,. ~ ~

CHs CHs

~-C~,o..

CHzb

CHs

(~.2.1s5) Similar synthetic procedures have been employed by Stelzer and coworkersz~27 to prepare disubstituted norbornene derivatives with cyanoor methoxybiphenyl as mesogenic groups (Eq. 2.186-2.187).

mr

~.lss~

90

••,,COCl.

2IPy, C H ~DMAP~ C O 0 ( C ~ ~ ~ ~ - C 2HO(CI~~~~~"C N

COCl

N

CO0(CH~~-~~N

(2.~sz)

Recently, such monomers have been successfully employed to manufacture a wide range of side-chain liquid crystagine polymers with an attractive thermal and especially thermotropic behavior.

2.5.3.9. Synthesis of Heterocydic Monomers Simple heterocyclic monomers can be prepared by conventional methods; for instance, 2,3-dihydrofur~ is obtained by the partial catalytic hydrogenation of furan, under controlled conditions, while 2,3-dihydro-7pyran, from ethylene and acrylic aldehyde, by Diels-Alder reaction 22s (Eq. 2.188-2.189). [Cat] "-

(2.1

In addition, dihydropyran can be readily prepared from furfuryl alcohol by dehydration over alumna at 3 50~ r~ (F-xl. 2.190)

'~

AI203,350~ CH2OH ' ' -H20

~ ~O

(2.190)

A variety of heterocyclic substituted and unsubstituted olefins can be efficiently obtained from heteroatom-containing dienes by ring-closing metathesis reactions, z3~These reactions are favored for the production of 5,6-, 7- and 8-membered tings in the presence of molybdenum or ruthenium catalysts that are tolerant toward heteroatom functionality. In one process, 1,4-dihydrofuran was readily obtained from diallyl ether in the presence of R~Os/Al203 or R~Os/Al20;/Bu4Sn as a catalyst (Eq. 2.191).

~

O~__~

=

(-~'~

(2.191)

91 Similarly, substitutod 2,5-dihydrofuran and 2,3-
=

~,,:,~--- P h

(2.192)

and 2-phonyl-2,3-dihydro-~-pyran (Eq. 2.193).

~",T/ph -~~0

~ ~ o ph

=

(2.193)

Substituted oxopins are also roadily obtained from unsaturated monocthers by ring-closing metathesis in the presence of molybdenum or mthonium carbone initiators (Eq. 2.194-2.195).

Ph~,.~.~..

[Ru]

o-../'=

Ph

Ph (2.194)

.-

[Mo]

__••Et O ~

~O

"Me

"11= 92%"-

Ph

(2.195)

Similarly, substituted ac,c ~ s have been prepared from unsaturated diothors in the prosonce of molybdenum initiators (F.q. 2.196).

Me 0-...../

"Me

"-

11= 89%

Ph

(2.196)

92 Analogously, nitrogen-, sulphur- and phosphorus-containing heterocyclic olefi~ have been prepared from the linear heteroatomcontaining dienes by ring-closing metathesis under the action of adequate metathesis catalysts (Eq. 2.197-2.199).

[Mo]. =._

Ph--N

~~q~

(2.197)

I

Ph

[Mo] ~

m

Ph-P

= [w]

/S-~

=

(2.198)

~'-p-~ I

(2.199)

Ph

Oxanorbornene derivatives. A large number of substituted and unsubstituted oxanorbomenes can be prepared by the Diels-Alder reaction of fiuml with a variety of dienophiles. Thus, the simplest representative of the series, 7-oxanorbornene, is readily available by condensation of furan with ethylene (Eq. 2.200). 0

When substituted furan and substituted olefins are employed, various substituted 7-oxanorbomenes can be produced by this reaction ~" (Eq. 2.201).

0

R

O + i1

(2.201)

93

On usingolefinswith functionalgroupsasa dienophile,Daubenand Krabbenhafl~s9prepared 7,-oxanorbomenebearing nitrile, ester, aldehyde and ether functionality (Eq. 2.202).

X

O =

~ X

(2.202)

When acetylene derivatives are used as dienophiles in association with furan compounds, oxanorbomadiene derivatives can be obtained by this way (Eq. 2.203). R

COOR'

+ III R

0 R

COOR'

=

COOR'

(2.203)

R 'COOR'

Further reaction of oxanorbomadiene derivatives with furan will form the corresponding dioxahexahydronaphthalene derivatives (Eq. 2.204).

~CC oR zRO + R~O 02R' R

~

(2.204)

RCo /2RR

7-Oxabicyclo[2.2.1 ]hept-5-ene-2,3-di~xylic anhydride was prepared by Diels-Alder reaction of furan with maleic anhydride~9~ (Eq. 2.205).

Co+Coo,

,f co,

(2.205)

Hydrolysis of 7-oxabicyclo[2.2. l]hept-5-ene-2,3-dicarboxylic anhydride produced 7-oxabicyclo[2.2.1]hept-5-ene d i ~ x y l i c ~ d 191 (Eq. 2.206).

94 CO~k

0/0

O

H20 "

I,,%,~ .COOH

=-

~ l ~ C OOH

(2.206)

Reduction of 7-oxabicyclo[2.2. l]hept-5-ene-2,3-dicarboxylic acid with lithium aluminium hydride formed 7-oxabicyclo[2.2.1]hept-2-ene-2,3dimethano1192 (Eq. 2.207). 0

COOH LiAIH4 OOH

.~.I~CH2 OH //.~.~/..CH20H

(2.207)

3-Mcthoxymcthyl-7-oxabicyclo[2.2. l ]hcpt-2-cnc-2-mcthanol w a s prepared from 7-ox~i~clo[2.2. l]hept-2-ene-2,3-dimeth~mol by the reaction with sodium hydride and subsequent treatment with iodomethane '92 (Eq. 2.208).

~

a. 1 Nail

CH2OH b. 1 CH31 CH2OH

CH2OMe CH2OH

'

(2.208)

Further on, 2,3-dimethoxymethyl-7-oxabicyclo[2.2. l]hept-5-ene was obtained from 7-oxabicyclo[2.2.1]hept-2-ene-2,3-dimethanol when two equivalents of sodium hydride and iodomethane were employed m~ (Eq. 2.209).

,~~fcC H2OH a. 2Nail H2OH b'2CH31 =

O

~..~.,CH2OMo ~ | 7"CH2OMe (2.209)

Alternatively, 7-oxabicyclo[2.2.1 ]hept-5-ene-2,3-dimethyl diacetate was prepared by esterification of 7-oxabicyclo[2.2.1]hept-2-ene-2,3dimethanol with acetyl chloride in the presence of pyridine ~ (F,q. 2.210).

~ . ~ C cH2OH 2 AcOCI "= ~ H0 2~ O A.CcH2OAc H2OH PY

(2.210)

95 Norbornene monomers for polydendritic polymers have been prepared by the condensation re,actions of 7-oxanorbomene-5,6-carbonate with suitable ben~lic alcohols ~ ' ~ (Eq. 2.211).

O

O

~~OC Hz'~~O(C Hz)I=H 9 2 HOCHz'~t~~OCH2.~~~)(CH2),zH \ OCH2~lCH2)lzH 7C Hz'~k~O(C Hz)IzH

>_oc.,_< >o,c.,,,,. CH2

O(CH2)12H

r

~//OC H2-~ /~'~O(CH2)lZH

o O --H2

'~

__

"-

~OOH2"~ ~O(CH2),2H ~OCH2"~'.. ~O(C Hz),2H (Eq. 2.211)

Azanorbornene derivatives. When pyrrole is used instead of furan, a wide range of 7-azanorbornene derivatives can be obtained by the Diels-Alder reaction with various dienophiles (Eq. 2.212).

~NH

*

(2.212)

N-Substituted pyrrole will give also N-substituted 7-azanorbornene derivatives (Eq. 2.213).

96 R~ N

N--R

+

(2.213)

2-Methyl-2-azanorbomene was prepared by the reaction of methylamine hydrochlofide with formaldehyde and cyclopentadiene (Eq. 2.214).

-HCI ~

+ CH20 + I'K31H2N--CH3

H20=-

CH3

(2.214)

In a similar fashion, 2-benzyl-2-azanorbomene was prepared from benzylamine hydrochloride, formaldehyde and cyclopentadiene (Eq. 2.215).

C

__~ + C1"120+ HCI'I"I2NHzC

-HCI -I"~O

(2.215)

l,l-Dimethyl-l-silacyclobutene, ~ a very reactive monomer, was prepared by flash high vacuum pyrolysis of diaUyldimethylsilane at 750~ (Eq. 2.216). \Si//_

' .

' 750"C~

\

EIsi/

(2.216) \

Other substituted sila-monomers, e.g., l-alkyl- and l-aryl-silacyclopentene, have been obtained by treating all~l- and aryldichlorosilanes with butadiene and magnesium. On this line, l-methyl-l-silacyclopentene and l-methyl-lphenyl- 1-silacyclopent-3-ene were readily prepared from methyldichlorosilane and methylphenyldichlorosilane, respectively, with 1,3butadiene and magnesium in tetrahydrofuran 2~ (Eq. 2.217-2.218).

(

+

HSiMeCI2

IVlg~HF c s ( Hi .~

Me

M HF + SiMePhCI2

..~

i Xp h

(2.217)

(2.218)

97 Analogously, l,l-dimethyl- and 1, l-diphenyl-l-silacyclopent-3-ene were synthesized by the addition reaction of dimethyland diphenyldichlorosilane, respectively, with butadiene, under the same conditions (Eq. 2.219-2.220).

~

SiMe2CI2 Mg/THF C S /Me

+

i XMe

=

+ SiPh2CI2

Mgnf CS /eh =-

ixp h

(2.219)

(2.220)

Functionally-substituted silacyclopentenes have been prepared by Heinicke ~ from silylenes, e.g., MeSiCI, MeSiOMe, MeSiNMe2, and dienes such as butadiene, isoprene and 2,3-dimethylbutadiene. For instance, methylchlorosilylene gives rise by the cycloaddition reaction with the above dienes to 1-chloro- 1-methylsilacyclopent-3-enes (Eq. 2.221). c, L ~ S ( - Me ,'."-~"

(2221, \Me Similar reaction os mcthoxym~ylsilylcnewill produce l-methoxy-]methylsilacyclopent-3-ene(F_,q.2.222-2.:223). --

+ [CIMeSi:]

+ [Me(MeO)Si:] ~

R~ + [Me(NMe2)SI:] ~ R

"

R/~

Si

+

(2222)

I\M e

R~L.~~ /NMe2 RT'~,,~ NMe2 R~,..jSI\M e + R,~Sk~Me (2.223)

"qt

The silylenes used as dienophiles in these reactions can be readily generated in situ thermally from disilanes (Eq. 2.224).

Me

Me

c~

cl

Me

,Me

400-550oc

.~

[CIMeSi:]

(2.224)

98 Further reactions of l-chloro-l-methylsilacyclopentene can provide a range of substituted silacyclopemenes suitable as reactive monomers for ring~ opening polymerization (Scheme 2.45).

C$i fOR \Me

/NEt \Me

CSi

Eh

m,,'~

~

....

~ O'~

/--x

ixMe

\Me --"NS/Me i

/H

CSi

Lj Me\ s/ f ' l

\Me

Scheme 2.45 2,3-B~5-silaspiro[4.4]nona-2,7-diene was prepared from benzyl(chloromethyl)dichlorosilane by intramolecular Friedel-Crai~ cyclization and subsequent addition of the intermediate l,l-dichloro-3,4benzo-l-silacyclopent-3-ene with butadiene and magnesium in tetrahydrofuran 2~ (Eq. 2.225).

~

C1"12-.SiCh AICI3 ~]~SiCh (

~S0

(2225)

Further treatment of 2,3-benzo-5-silaspiro[4.4]nona-2,7-diene with catalytic amounts of n-butyllithium and fIMPA resulted in the formation of a dimer, 2,3 12,16-dibenzo-5,10-~siladispiro[4.4.4.4] octadeea-2,7,12,16-tetraene (Eq. 2.226).

~Si~

nBuU/I-MPA TPF/-78~

(2226)

99 Likewise, dimerization of 2,3-dimethyl-5-silaspiro[4.4]nona-2,7-diene in the presence of n-butyllithium and ItMPA gave 2,3:12,13-tetramethyl-5,10disiladispiro[4.4.4.4]octadeca-2,7,12,16-tetraene (F-4. 2.227). 2 ~Si~

nBuLilHMPA -THFI-78~

i:~

(2.227)

By the same route, l,l-divinyl-l-silacyclopent-3-ene yielded sil~cant amounts of the dimer, 1,1,6,6-tetravinyl- 1,C~:lisila-3,8-cyclodecadiene along with the ring-opened polymer2~ IF_4. 2.228).

2

THF/-78~

.~J

"

i X~.

(2.228)

Substituted gennana- and stanacyclopentene were prepared by ringclosing metathesis reactions of the corresponding Ge- and Sn-containing dienes under the action of adequate metathesis catalysts TM (Eq. 2.2292.230). Me\ /~,~ Re2Os/AI203/Bu4S n

\Me BU~sn/~ au/ ~

.

[VV]=CHCMe3= '

CSn/. Bu

(2.230)

au

2.5.3.10. Synthesis of Macromonomers

a~-Norbornene-ended polystyrene macromonomers have been prepared from polystyryllithium capped with ethylene oxide and the resulting polystyrylethyloxide condensed with norbom-5-enyl-2-e.arbonyl chloridez3z~3 (Eq. 2.231-2.232). O ,B="1.= ,B= ~o~ ~ (2231) It

100

(2.232)

- UCI

Similarly, polybutadienyllithium treated with ethylene oxide and then condensed with norbom-5-enyl-2-carbonyl chloride gave rise to norbomene-ended polybutadiene macromonomersTM (F~. 2.233-2.234).

Toluene"- "

=---

"-

OeLJe

fJ•COCl ,

(2234)

=---

- LiCl

Several other (z- or r macromonomers, having as host polymer for instance l~lyethyleneoxideTM or Imlyethyleneoxide/polystyrene block copolymer, were also prepared by this way~ (Eq. 2.23 5-2.237).

c6~ ~ L i

+ n+l~

11~ED~

~-Z

MeOH=

LP

(2235)

PhzCH~

TI"IF ~

OK

(2.236)

101

(2237)

Polystyrene macromonomers, containing a norbomene unit within the chain, suitable for ring-opening metathesis polymerization, have been prepared in three steps by anionic polymerization of styrene under the action ofsec-butyllithium, capping the basic polystyryl anion with propylene oxide to produce lithium 2-polystyrylisopropyl alkoxide and further condensation of two equivalents of lithium 2-polystyrylisopropyl alkoxide with bicyclo[2.2.1]hept-5-ene-2,3-dicarbonyl chloride 93 (Eq. 2.238-2.240).

(2.238)

oE)Ij~

I~

-2L~= '~T~--y

(2.239)

-'L'1--~1-'~' (2:~)

Such macromonomers have been successfully used to the manufacture of polymers with special architectures such as grafted, comb-like or other related structures.

102 2.6. References

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