Regioselectivity in lithium, sodium and potassium chloroallyl systems. An ab initio-theoretical and experimental study

c+404020/91 s3.00+.~

TerrahrdronVol.47.No.41,p~.8139-8~521~1 RmtedinGrelu Britain

RRGIOSELECTIVITY

IN LITHIUM,

0

SODIUM

AND POTASSIDM

AN AS INITIO-TEEORETICAL Carlo

Glauco

Canepa,

Istituto

di Chimica

Via Pietro

and Paolo

Organica

Giuria,

CHLOROALLYL

AND BXPERIMRNTAL

Tonachini

7

dell'

I-10125

1991 Pagamon Press plc

SYSTEMS.

STUDY

Venture110

Universita‘

Torino,

Italy

(Received in UK 28 May 1991)

Abstract The comp;~~$u;tr~;$ural and,electronic features of the title describe the potassium elect%$f%s a?ha~orfhe'n%?~~ous carbonyl regioaelectivity with compounds. Some experimental results con irm this expectation.

;;rnpo;;$s 1ithiA

Introduction In the its reactivity This

system

reacting depending presents Ccl2

gem-dichloroallyl-lithium

last years atudied

has

with

experimentally

been

shown

carbonyl

to

attack

spectrum

to a complete

laboratory,3

providing

Ccl,-selectivity

an

Mauze'

hand

studied of

compounds

(Scheme

1).

when

Indeed,

it

from a complete the reactivity

experimentally

result

and

of attack

atom.

going

On the other

recently

products

carbon

interesting

carbonyl

nucleophile

different

distributions

synthesized

and coworkers.'-2

ambident

carbonylic

attack?

has been the

toward

the

product

CH1

gem-dichloroallyl-potassium

as

yielding

on

of

Seyferth,

behave

compounds,

on the substituents a whole

by

has been

an

of

in this complete

almost

O-M' RR'C=O

+

(C12CCHCH,)-M'

+

RR'&-Ccl=-CH=CHz

FM* CIIC=CH-CH2-CRR'

+

(M=Li,Na,K) Scheme

The rationalization factors

that

properties degree

can

of aggregation and Schleyer

while

allyl-sodium

symmetric, function

results affect

and

of interaction

has

of the counter-ion in principle bonding 8739

such

as:

been

shown

increasing with

from

(i)

the unknown

hy Winchester,

(ii)

allylic

free anion,

where

dimar,

to be present

temperature:

the substituted an almost

situation

electronic

itself

dggregation

of

and

as an asymmetric

been argued

have

structures);q with

by the existence

structural

conditions

allyl-potassium

to a true

the

itself

in the usual

increasing

complicated

is

systems,

these

monomeric,

it ranges

ion pair,

of

(allyl-lithium

of temperature,

in the monomer: separated

of these

to exist

presumably

1

principle

and the behaviour

Bauer

degree

in

(M=Li)

the cation

as

is a the system

a solvent and the

8740

c. CANEPAet al.

anion

would

interact

In the present has been will

assumed

be the

degrees taken

into account

the

molecules, under

the

as a first

study).6

interpretation different

The

lithium,

the

distribution by a hard

and

connection

of the

can be discussed

could

determine with

this

purpose,

also

A comparison

allyl-lithium studied (the

Theoretical

can

also

minima

by complete

parameters

in

first

function

of the

features Their

of the

electron

the possibility

reactions

substituted between

of attack as a factor

mono

systems,

a

to

stable

In

of gem-dichlorobenzaldehydes

that

different

are

and dichlorohave

at the same computational

shows

diffuse

been level

regioselective

using

on

and on a VAX Station

chlorine.

on carbon This will

on an IBM 3090 computer 3200+3150

cluster

shell

been

carried

3-21G

basis

out at set,=O*

atoms

and with

set, containing

neither

be labeled

have been performed

were

and chlorine

basis

have

of the geometrical

computations

split-valence

on the cations,

The computations

of programsll

the

structures

optimization

These

sp functionszob

d functions

nor d functions

this paper.

unconstrained

methods.s

level of theory, with

corresponding

and

by gradient

polarization diffuse

a

of the markedly

the dichloro).*

The energy

augmented

is also

of a soft electrophile.

drawn

paper7

system

attempt

can be examined

of some

be

solvent

shell,

monomers.

with

with

a lithium,

by considering

and electronic

fluoro-substituted

in a previous

to

by

anions,

oxygenated

above)

systems

with

"no

method

determined

the RHF

solvation

attack

the results

gem-difluoroallyl-lithium than

of

-potassium

and the analogous

theoretically

behaviour

series

and

first aims

connection

i.e.

them

with

some

HOMO polarization

are

ally1

with

these

anion

studied

comparing

discussed

structural

the orientation

-sodium

and

dichloroallyl

in

while

allyl-lithium, reported.

substituted

investigation

by

thus

can be modified

a

approximations

potassium

electrophile,

for

are

and

the different

allylic

of the anions

species

shown

investigation

situations,

systems

two

(how this picture

present

on the basis

sodium

extreme

The

association

approximation

(within

two

of deaggregation

Moreover,

the substituted

of

metallated

regioselectivity

counter-ion,

which

cation

of

is under

1,1-dichloropropenide,

from the tight

or potassium

the interaction

just

structures

and

originating

with

interaction".

stable

situation

equilibrium

modelling

"tight

an extreme

communication).6

of the cation

by

and

1-chloropropenide

sodium

study

of a separate

of interaction

determining

significantly.5

(the monomer-dimer

subject

interaction"

those

much more theoretical

using

3-21+Gl*l

at CSI-Piemonte

at the Istituto

throughout

the GAUSSIAN82 (Torino,

di Chimica

and 88 Italy)

Organica.

Regioselectivity in Li, Na and K chloroallyl systems

Results

8741

and discussion

Structural

features

out at this

same

found

be

to

structure.

(Figure

stable

the Ca carbon

1;

CCC planes

the

in

of

is pyramidalized

and reported

to atom

study,' ally1

only in

a

carried

anion

completely

and dichloro

was

planar

ally1

anions

in the gem-disubstituted

anion

Angstrom,

X are defined

in square

of

the mono

lengths

bond

relevant

In a previous unsubstituted

correspondence

structures

RHF/3-21+G[*l

angles

level,

only

The optimized

show that

dihedral

of the free anions.

computational

as angles

angles

in degrees;

between

the XCC and

brackets).

1.062 "_'-'"-._' I.076 1.077 " 122.1

i'

115.3 '14.'

r c

116.6 l.6¶6_,--Cl _--

_

I.366

1.373

\ I.@66

130.1

"

126.5

b

a [170.4] 120.6 116.7 H-s_ '-076 1 H III., I.O76-‘C-c-C 1.072/ I.466 H 122.1 1.331 126.6

116.1

'\ \ \

[-6.0)

\\ I.667 \ \ \ Cl

I.603 106.6 \ [24.611X

(136.1)

122.2

d

104.1 [135.5]

C

Figure

The degree

of pyramidalization

( z angle,

in

description the ally1 system

of the electronic anion

with

of the CClp

is thus

group

leads

for

chloropropenide the CCC plane, bears

some

analytical minimum, to the Ccl2

to a

double

pyramidalized

Hessian

to

This

structure

localized

CC

shows

that

(0.004) is

is dominated less

stable

l,l-dithrough

optimized

critical

geometry

(Fig. Id). The

anion

The Hessian

than

JZ

by the ca-Cp

by reflection

by the

of

the tipical

equivalent

whose

ally1 this

as shown

Two

obtained

and that

delocalized

approximate

structure,

frequencies.

fully

lc the

The pyramidalization

system, that

in Fig.

between

species

atom.

bonds.='

unsubstituted

computation

eigenvalue

carbon

structures,

no imaginary

is reported

difference

of the allylic

lengths,

by a planar the

anion main

of the dichloro

terminal

rather

are connected

showing

group.

of a

and

resemblance

lowest

structure

(1.331 ii) bond

single

The

the desappearance

disubstitution

(1.480 fib and C/?-Q values

in the dichloro

bracketsl.la

round

1

point

is another

eigenvector

inversion

motion

the pyramidal

related of the

(Table

1).

8742

the

In

case

structures, are found center, ally1

close

1-chloropropenide,

with

the CC1 bond

to be planar

features

case of double

length were

some pyramidalixation features

will

was present

of the molecular

be examined

below

’ ally1

anion,

orbitals

in

are 8.

bond

rather Similar

but in the

pyramidalized

too.

electron

The

the free anions.

and

structural

distribution

for both the free and metallated

Total

1.387

was more

in 1-fluoropropenide the

carbon

the Ca-Cg

values

and difluoropropenide,'

both

bond,

at thea

less from that of the

1.379 ii. These

the a carbon

TABLE Free Anions.

depart

the

mono

determine

non-equivalent

to the Cp-Cy

the syn conformation,

in

for

possible respect

not pyramidalized

length

substitution

just discussed

polarization

bond

value

found

fluorine

Being

considering

d and the Cp-Cy

to the CC bond

two

anti with

1-chloropropenide

For instance,

is 1.375

structural

of

the

syn and

(Fig. la,b).

the structures

anion.

length

of

and the

These

effects

anions.

1

and relative

energies.'

E

OE

EOMO polarization.b

P(ca)/

p(q)

I-Chloropropenide

syn planar

la

-572.635579

0.00

1.295

anti planar

lb

-572.631840

2.35

1.156

pyramidal

lc

-1029.473230

0.00

3.906

planar

Id

-1029.466678

4.11

1.705

l,l-Dichloropropenide

a: RHF/3-21+G[*l

energies

b: the polarization squares

of the atomic

have

of

been found

associations

with

bond

lengths

in ingstrom,

atom

X are defined

the

metal

angles

as angles

differences

in kcal mol-z.

for Ca and Cy as the sum of

coefficients.

metallated

for both

an alkali

energy

is computed

orbital

features

Structural

structures

in Hartree,

of the HOMO

anions,

in correspondence

counter-ion

(Figures

in degrees;

between

the

Several

species.

dihedral

stable

to different

2-4; RHF/3-21+G[*l

angles

XCC and CCC planes

relevant

to an

and reported

in

parentheses). The optimized

Lithium.

geometries

for the

while

those

propenide-lithiumlo

system

are shown

in Fig.

2c,d.

2c lithium

to the a allylic

carbon

system

atoms

are

shown

in

is bound

("external"

Fig.

lithium) .

2a,b

On the

lithium for

1-chloropropenide

the

l,l-dichloro-

In the structures

2a and

atom and to one or two chlorine

contrary,

in

the structures

2b and 2d

Regioselectivity inLi,NaandKchloroallylsystems

the Ca

both

bridging

Cy atoms

counter-ion

show that while structure true

in

the

is slightly

dichloro

closer

involved

lithium).

The

system

stable

system.

to that

are more

substantially

monochloro

more

for the dichloro

in general

are

("internal"

than

the

pyramidalized

energies

one, the

and

allyl-lithium, show

longer

ca-cg

with

the

(Table

(or

of the monochloro

unsubstituted

(zvalues)

bonding

"internal"

"external"

The structures

of

in

relative

the

the

8743

2)

bridged) reverse

is

systems

are

while

the

and shorter

bond lengths, respectively. These features (related to a more CB-Cr pronounced localization of the electron distribution to a "double bond zone" and a "lone pair the

"internal"

zone")

one,

are more

for both

evident

in the

the monochloro

[-64.71 120.5

"ex.ternal" structure

and dichloro

than

in

systems.

Li

2.OOS

[175.9] “-120.7 i.oGl--c I.O7S/ H

I.083

119.5 109.7

r

-=-c 1.326 122.1 i-5 .S]

/

i .473 I31

‘\

.S

‘\ 2.04S

I .I381 ‘”

113.1

\

jp:,c1

(130.0)

\

[i22.2'

b

a

Ll

81.0

2.505

[-52.41

2.003 /\

[lse.S]

120.0 I

/

;;_,/‘-ond ‘13.’\,

1

I ::75/ H 109.1 (148.3)

Cl

'\ Cl

t"'61

II8.6\

I.3so,27~QI_4 .-.m _ Z‘zL.U [-21.9]

109.4 [124.S]

-Cl

(131.2)

In the

a structure

\ Cl

li7.0 [158.4] 112.8 [26.S]

d

Figure

optimize

I.767

-.__

I.846

C

Sodium.

144

case with

of

sodium

the counter-ion

the geometry

shown

in Fig.

to the plane

of the allylic

3a, where carbon

the

atoms.

2

1-chloropropenide in an "external" Na-Ca

bond

Attempts

any

attempt

position

is almost

to

yielded

perpendicular

to find a structure

with

C. CANEPAer al. .

8744

sodium

bridging

sodium

appears

defined closer

between

to be stable

for lithium to the

between

latter,

the two

in a position

the

cation

carbon

stable

(Fig. 3b), and

Systems.

Total

Thus

between

those

the situation

bridging

the case

of sodium

found:

the cation

one

and relative

energies.-

EON0 polarization.b P(ca)/

AE

P(q)

I-chloropropenide 2a

-580.071623

1.00

1.527

-580.073224

0.00

1.493

l,l-dichloropropenide

external

2c

-1036.898437

0.00

1.626

internal

2d

-1036.892591

3.67

3.124

I-chloropropenide 1.303

-733.551911

3a

syn

l,l-dichloropropenide

external internal Potassium

3b

-1190.388039

0.00

8.363

3c

-1190.377678

6.50

9.674

I-chloropropenide 4a

syn Potassium

0.977

-1168.745113

l,l-dichloropropenide

external

4b

-1625.502062

0.00

10.773

internal

4c

-1625.492972

5.70

9.552

a: RHF/3-21+G[*l

energies

b: the polarization squares

(apart

cation-Ca-Cfl

in Hartree,

of the HOMO

of the atomic

"external"-Na

structure

structure from

angle:

the ca.

Both

energy

difference

IIinternal" structure,

would

in kcal mol-l.

for CQ and Cy as the sum of

from

for

kcal and

the

Li, molW1

in

mainly

in the

bond

length)

1610

for Na. The two stable

in

favour

large

the

operate

"external"-Li

analogous

ca.

cation-Ca

longer

by ca. 6.5

differences

coefficients.

differs

1340

differ

energy

is computed

orbital

structures this

an

2

2b

Sodium

with

in an "internal"

ayn internal

Sodium

is

as

syn external Lithium

The

In

were

result.

3a.

E

Lithium

although

atoms.

with

to that of Fig.

same

be considered

structures

another

the

is intermediate

cannot

TABLE Metallated

that

"internal";

atom

allylic

two

(Fig. 3c), similar

position

and

sodium

terminal

produced

and 7 carbons

as "external"

l,l-dichloropropenide "external"

the u

Na-Cy

favour

of

of the

"external"

distance

even

one. in the

a Ccl,-regioselective

Regiosekxivity

attack to

by a carbonyl

play

an

inLi,NaandKchloroallylsystems

electrophile,

important

role

if it is assumed

in

stabilizing

that

a

8745

the counter-ion

four-center

has

transition

structure.15 [-B4.6] 109.2

%:;I

Nm

N.

2.213 2.226 I Nf.j;:::~ ,‘.b”,‘4”

/ H

,.0*2

y

::x:i:

-C-C-C I .a34 yz~]

I

I .43a

‘\I

‘30.3

\

.073 H

\

iia.

[ia7

1.841 \

110.4 124.3,

(I33.3)

CI

a

[I74 .o] N-120.4 1.074--c,.072 “0

1.073

N

III.3

t.923 122.3 [*.a]

(143.7)

b Figure

As was the case with

Potassium.

was

found

to be stable

counter-ion carbon

cannot

atoms.

structures with

were

closely

"internal"-K lengths) ca.

found: in

above

Ccl,-regioselective

in

those

obtained

operate

of

the also

by a carbonyl

cation (Fig. for

(apart

for sodium.

(Fig.

between

sodium.

these The

from the different

this

species

electrophile.

stable

results

for

"external"

and

cation-Ca

structures

one.

"external"

two

(Fig. 4b), and another 4c):

The two stable

for

the

4a);

the CU and Cy

1,1-dichloropropenide

position

are similar

favour

bridging

an "external"

"internal"

attack

as

1-chloropropenide

position

"internal"

potassium

one with

optimized

would

an

potassium

sodium,

considered

of

parallel

structures

to those

5.7 kcal molml

discussed

an

in

be

In the case

the cation

potassium

only

again

3

The same in

bond

differ

by

factors

favour

of an

8746

c. CANEPA etal.

[-58.9] 37.4

K

2.633 \ [171.8] "220.4

*,3.4 ,H 111.5

1.073

\

1.074 Ns-ci.s7i-c c I.395 1.074 / 123.6 H 122.3 [-15.0]

103.3 1127.01

(ls3.3)

b Figure

Electronic determine should which case

be sensitive)

of attack

system

structures

the planar

consistent

stable

by the density

the

both

mono

pyramidal

zone"

plot

A similar

system.

appears

structure

and

5,

is

and

rather

The

is

anions of

found (lb,

effect

m

to

orbitala,

importance

of single

distribution

electron

allylic

density

for

the

Id).

On

of leas the

for the more

distribution

appears

stable

planar

contrary,

from a ca "lone pair

in

a ca-cy

zone".

to

For the more

above.

a delocalized

(1~)

(on a

(la and lc), and for

(la), the description

that

of

in the

and double

of them

electron

discussed

features

electrophilea

to it) is plotted

1,1-dichloropropenide

separated

hard

molecular

free anions

features

close

the

the total

parallel

(Id).

description

as clearly

where

of 1-chloro-propenide

dichloro

structure

The

and dichloro

the structural

structure

of

structural

which

be of particular

on the electron

in Figure

of the mono

with

planar

should

The

(to

electrophile.

substitution

dichloro

anions.

polarization

(HOMO)

0.5 i from the CCC plane

stable

of

soft

by a

terminal

free

distribution

the

and

occupied

can be examined

plane

of the

electron

the

the highest

chlorine

be

features

both

4

provided IC allylic structure

the

case

"double

of

bond

8141

Regioselectivity inLi, Na and K chloroallyl systems

Figure

Electrostatic plane

of both

could thea

the

sense

diaubstituted

anion

anion.

and lc structures are shown

and

at

electrophile,

an attractive

and y positions,

monosubstituted

plane,

obtained

-Pa

a hard

show that

"above",

of

potential

approaching

with

a preference

and

for

corresponding

The HOMO

the The

squarea ratio

Table

polarization

for each

1 .

substituted

atom

between

carbon

1-dichloropropenide.

can be

atomic

the Caand

It can be seen atom,

the

from the CCC

allylic

potential

for the former

latter

in

system

from

in correspondence

the

in the case

case

the

of

relevant

to the more

to

distance

of 2.0 ft from the CCC

a

stable

la

6.

X in the

of the HOMO

the

distances

maps,

Figure

defined

different

electrostatic

Two of these

in Figure

5

6

expressed

molecule; orbital

more

the

value

coefficients

Cy P values that

in terms its

belonging

is reported

HOMO

significantly

always

is in

of'a parameter, is given

P(X),

by the sum of to that

in the third polarized

atom.

column toward

1,1-dichloropropenide

of the

than

8748

c. CANEPA et al.

These anion

results

the charge "orbital CClz

show that,

(pyramidalized

distribution,

interaction

terminus

expected

a

have

distribution

On

still This

potential

the CCC plane.

potential this

attractive

potential

effective.

For lithium carbon

attractive

feature

is

overwhelmed

contrary

the

to the allylic

carbon

deeper

becomes

different

features

metallated

at

part

at closer at

namely

from the

the electron

distances

larger the

distances, system

repulsive

least

where

show

field;

two

in

part

the only On the

depressions

obvious

of the

in a

from the that

from the geometries

positions

the less

provided

to the y carbon.16

It is fairly

relative

by the

is much

to the potential

plots

of

R from

generated

and the one originating

distances.

is (as

is the zone of strongly charge)

of

cation

skeleton,

originate

species,

also

potassium

correspondence

anion

7) by a series

different

maps

is in correspondence

and

sodium

three

positive

the

the

the overall

of

(Figure

contribution

by

Although

polarization

these

allylic

to an

toward

and by the P ratios).

again

at

any attractive

zone of the plots

the monochloro

clear

present

sensitive attack

to

hard and soft electrophiles

species.

approaching

the

more

sensitive

contrary,

shown

of

the free dichloro more

their

maps

computed

is

of

a

is

feature

(for an

counterion;

by thea

maps

The dominant

of

to direct

way with

potential

is observable.

electrostatic

the

of the metallated

no net charge,

case

electrophile,

electrophile,

prefer

in a different

features

extreme

soft

would

by the electrostatic

repulsive

the

both a hard

of the molecule.

Electronic systems

and

factor",

to interact

indicated

for

structure),

these of the

acarbon

and

the counterion. The HOMO polarization (third column). exception

It

is reported generally

of 4a); this

is associated

system

important

orbital

electrophile's

In the

interaction

with

rather

energy

the HOMO of the

the electrophile's centered

HOMO's

the

LUMO;

carbonyl

interactions as indicated

schematically

is maximized state.

It

allylic

HOMO

group

in Figure

is polarized

if the alkali can be noted

metal

that

in the direction

of

the

with

the oxygen atoms metal

the carbon

atom

with

Because

approach

this

its a

with

species, the HOMO

interaction

in the transition

significantly bound

the

two orbital

the metallated

atom,

the

have also

interaction Thus

significant.

and oxygen

because

species

whose

on

the more

thus diminishing

ofref7forLi.

toward

the anion

between

The association

energy,

dealing

3

that

the metallated

be

when

in energy)

be

on the counter-ion,

could group have to be considered when

of the carbonyl

to

HOMO.

nucleophile's

high

2

(with the

by a soft electrophile

is rather

expected

terminus

pronounced

of attack

HOMO

for Ca and Cy in Table

substituted

to be more

is

significantly

LUMO,

the

case

interaction

LUMO and the

lowers

as P ratios

appears

(where the allylic

counter-ion

low

feature

to Na or K.

an anionic

again

favours

polarizes

to it, and

the

the LUMO

Regiosele-ctivity in Li, Na and K chloroallyl system

-7-y

:: + :: ::

8749

-

:: _.

: i ; : :

2.2

R(i)

2.0 Figure

7

8750

c. CANEPA ctal.

of the carbonyl orbital8

would

electrophile

group

is

as a consequence

approached

structure,

polarized

as

the

found

Therefore,

factors

in a

favoured

on

the

distribution structural that

and features

carbonyl

addition

indications the HOMO found

but against monochloro

ana

shown

the counter-ion electrophile mostly

involved

(compare

to

attack

Zc,

in

7,

dominant

of metallated

Carbonyl

compd.

P-value case,

repulsive

and

appears This

carbon.

system provided

in some

region

ratiosb

situation

lOO:

o-ClC.H.CHO


p-ClC~H.CHO


(73)

lOO:
with

(70)

(75)

lOO:
(65)

(65)

lOO:
(60)

(68)

lOO:
(67) (63)

o-MeOf&H.CHO


(68)

lOO:
(65)

lOO:
23:77

(75)-

lOO:
(60)

lOO:
(65)

o-MeC,H,CffO


(63)

lOO:
(60)

p-MeCsHeCHO


(68)

lOO:
(68)

3.12 mmol.

f: data

by

from ref.

lOO:
%H n.m.r. product.

(65)

compound,

carbonyl

3; t-BuOK,

a hard

K=

(70)

isolated

for

respect

some carbonyl

lOO:
20 ml; T= -95 OC. b:

maps

is determined

p-MeOCs?i4CA0

THF,

for Na,

and yields".

p-CF&sHJHiO

(25%). c: in parentheses;

be

3

15:85

mmol;

by

surrounding

to discourage

Nag

mmol;

could

the

structures.

PhCHO

2.5

the

are for Li as

potential

feature

Lid

a: 3,3-dichloropropene,

to

for the

pattern

similar

the

(8019

be

electron

less favourable

where

CCla:CEa

those

ratios

Electrostatic

3,3-dichloropropene

compounds:'

the

structures

oppose

all cations

TABLE Reactions

could

related

regioselective

Here

6) by the geometrical

to

the following

attack

for the Li dichloro maps

2).

are for

if the

transition

and 4b (with the possibility

as in the dichloro

for K (Table

systems,

transition

a different

way,

of formaldehyde

discussed,

3b

the

on the substituted

Figure

attack

counter-ion:

just

systems.

(not shown)

is the

the

the frontier

four-center

electrophilic

electrostatic

for Li in Figure

attack

an

atom,

favourable

a

the

On the contrary,

Finally,

attack

systems

that

Figures

monosubstituted

to a CHCl

via

for

closer

from the

polarization.

favourable

in

reaction).

obtained

in the

to those

be

a more

system

polarizations

shown

the counter-ion

way

atom

HOMO

in

carbon

for the Na and K dichloro

sharp

carbon

the

interact

allylic

computationally

methyllithium.15 indicate

toward

2.5

on the crude

d: data

3.12 mmol.

mmol; reaction

from ref. g: total

LDA,

2.5

product

3. e: t-BuONa,

yield.

Regioselectivity inLi,NaandKchloroallylsystems

conclusions

The

experimental

results

various

with

counter-ion attack

of

of some

substituted

when

system

the same

compounds

reactions

with

by treating

tert-butoxide

the reaction

the

in

correspond

with

the

is the

compounds

with

On the

of sodium

to an attack

prepared

have

presence

react

carbonyl

in the presence

derivatives

compounds

lithium

for CH= terminus.

out

products

with

3,3-dichloropropene When

all the tested

LochmannXe

that working

the carbonyl

compared

3).

preference

are carried

and

be

(Table

anion

organolithium

we assume

Similarly,

can

of the metallated

a marked

reactions

SchlosserX7

site.

study

benzaldehydes

or pota'ssium tert-butoxide, the CClz

present

of the gem-dichloroallyl

the allylic

contrary,

the

8751

at

organopotassium

potassium

of sodium

alkoxide.

and potassium

gem-dichloroallyl-sodium

and

respectively.

-potassium,

Experimental The apparatus

and the reaction

reactions

of gem-dichloroallyl-sodium

atmosphere

in flame

diisopropylamine Fluka, The

and were

carbonyl

spectra

IH N.m.r

connected

recorded

with

n-butyllithium

a

sodium

allowed

within

-95 OC. After

a

few

(0.30 g,

the addition

layer was

mixture of

to reach

separated

The combined

the

minutes 3.12

mmol)

THF

was

added

then

stirred

temperature,

and the aqueous organic

phases

Oc!)

solution

ml,

at -95 V,

A mixture

carbonyl under

for 2 h under 3.9 mmol)

then

poured

kashed

of

dissolved

and the apparatus

dropwise

one extracted were

(1 ml) was added

temperature.

was

(0.5

column).

flask was cooled was added

Mass

detector

tert-Butoxide.

in hexanes)

and of the desired

C1Si(CH3)3 room

the

the R-24B

standard.

capillary

(-20

to

selective

THF

cooled

further

Perkin-Elmer

of Sodium

1.6 M solution

equilibrate

anhydrous

The reaction

organic

B mass

anhydrous

previously

without

according

silicone

and from

to the reaction.

as internal

5970

in

(0.27 g, 2.5 mmol)

was allowed

(15 ml).

mmol) a

for 15 min to

mixture

ether

to

After

in 1.0 ml of

5 min.

used

on a Hitachi

methyl

i.e. 2.5 mmol;

tert-butoxide

3,3-dichloropropene (2.5 mmol)

2.5

syringe (1.6 ml,

to stand

were

out with LDA in the Presence

(0.25 g,

in 20 ml of dry THF. then

(cross-linked

prior

TMS

inert

tert-butoxide

synthetized

HP

a

All the

out under

n-Butyllithium

Torr)

and

using

with

THF.

sodium

(0.1

recorded

spectrometer

described.= carried

anhydrous

Aldrich,

was

were

at 70 eV

Carried

Diisopropylamine dropwise

spectra

to a HP 5890 GC

Reaction

likewise

commercial

were

resolution

were

were

vacuum

3,3-Dichloropropene

literature.=-

previously

from

under

compounds

been

with

glassware

purchased

sublimated

purification.

60 MHz high

dried

were

for gem-dichloroallyl-lithium

procedure

has

and gem-dichloroallyl-potassium

twice with

of

compound stirring argon

at

the reaction in water.

The

with

diethyl

brine

(10 ml)

8752

C.CANFLPA~~al.

and dried pressure establish mass

with

anhydrous

Na,SO,.

and the residue the CCla:C&

spectra

ratio.

in agreement

The

was analysed

with

solution

All the obtained those

was condensed

by =H n.m.r.

previously

under

spectroscopy,

compounds

show

reduced

in order

III n.m.r.

to and

reported.'

Aknowledgements This work has been supported by the Minister0 dell'Universita' e della Ricerca Scientifica e Tecnologica, the Italian C.N.R. and CSI-Piemonte. References and notes (a) Seyferth, D.; Simon, R.M.; Sepelak, D.J.; Klein, H.A. J. Org. Chem. 1 (b) Seyferth, D.; Murphy, G.J.; Woodruff, R.A. 1980, 45, 2273-2274. Chem. 1974, 66, C29-32. (cl Seyferth, D.; Murphy, G.J.; J. Organometal. Woodruff, R.A. J. Am. Chem. Sot. 1974, 96, 5011-5012. (d) Mauze', B. J. Organometal.Chem. 1979, 170, 265-279. (e) Mauze'. B. J. Organometal. Chem. 1980, 202, 233-239. (f) Seyferth, D.; Wursthorn, K.R. J. Organometal. Chem. 1979, 182, 455-464. Seyferth, D.; Murphy, G.J.; Mauze', B. J. Am. Chem. Sot. 1977, 99, 5317-5330. Canepa, C.; Cobianco, S.; Degani, I.; Gatti, A.; Venturello, P. Tetrahedron 1991. 47, 1485-1494. Winchester, W.R.; Bauer, W.; Schleyer, P.v.R. J. Chem. Sot., Chem. Commun. 1987, 177-179. on carbanion-cation interactions, see: Smid, J. Angew. For a review Chem., Int. Ed. Engl. 1972, 11, 112-127. in preparation. Canepa, C.; Tonachini, G. manuscript Tonachini. G.: Caneoa. C. Tetrahedron 1989. 45, 5163-5174. Seyferth,.D.;.Simon-, R.M.; Sepelak, D.J.; Klein, H.A. J. Am. Chem. SOC. 1983, 105, 4634-4639. (a) Schlegel, H.B. J. Comput. Chem. 1982, 3, 214-218. (b) Schlegel, Theoretical Organic Chemistry, Csizsmadia, I.G.; H.B. in Computational Daudel, R. Eds. Deidel Publ. Co. 1981, 129-159. (cl Schlegel, H.B. J. Chem. Phys. 1982, 77, 3676-3681. (d) Schlegel, H.B.; Binkley, J.S.; Pople, J.A. J. Chem. Phys. 1984, 80, 1976-1981. J. Am. Chem. Sot. 1980, (a) Binkley, J.S.; Pople, J.A.; Hehre. W.J. 10 102. 939-947. (b) Clark, T.; Jemmis, E.D.; Schlever, P.v.R.; Binkley, Chem. 1,978. 1.50; 1. J.S.; Pople, J. A. J. Organ&met. Binkley, J.S.; Frish, M.J.; DeFrees, D.J.; Krishnan, R.; 11 GAUSSIAN 82: CarnegieWhiteside, R.A.; Schlegel, H.B.; Fluder, E.M.; Pople, J.A.. Mellon Chemistry Publ. Unit. GAUSSIAN 88: Frish, M.J.; Head-Gordon, M.; Schlegel, H.M.; Ragavachari, K.; Binkley, J.S.; Gonzalez, C.; DeFrees, D.J.; Fox, D.J.; Whiteside, R.A.; Seeger, R.; Melius, C.F.; Baker, J.; Martin, R.; Kahn, L.R.; Stewart, J.J.P.; Fluder, E.M.; Topiol, S.; Gaussian Inc., Pittsburgh, PA, 1988. Pople, J.A.. angle z is computed as the angle between the CUC$l 12 The pyramidalization bond and the normal to the CHCl or CClr+ plane (a planar structure has z = 144.70). c =90.00, while a tetrahedral arrangement gives level the CC bond length values for ethane 13 At the same computational and ethene are 1.542 and 1.320 A respectively. Preliminary computations on this system allowed to discuss its regio14 Baima. R.; Canepa, C.; Degani, I.; selectivity: Angeletti, E.; Tetrahedron 1989, 45, 7827-7834. Tonachini, G.; Venturello, P. 15 Kaufmann, E.; Schleyer, P.v.R.; Houk, K.N.; Wu, Y.-D. J. Am. Chem. Sot. The attack of formaldehyde on the a and y 1970, 107, 5560-5562. positions of lithium and sodium 1,1-dichloropropenide is under study. show an Q carbon depression Similar maps for Li-difluoropropenide' 16 deeper than they . 17 Schlosser. M.: Hartmann, J. J. Am. Chem. Sot. 1976, 98, 4674-4676. Lochmann,.L.;.Lim, 18 D. J; Organometal. Chem. 1971, 28, 153-158. King, W.H.; Smith, H.A. J. Am. Chem. Sot. 1950. 72, 3459-3462. 19