Solvolysis of 9-substituted 10-anthranyl systems

Tetrahedron Lettera No.26, pp. 2475-2480, 1967.

Ltd.

Pergamon Ress

SOLVOLYSIS OF 9-SURSTITUTED

lo-ANTHRANYL

Printed in Great Britain.

SYSTEMSlay b

Richard LeutelC and S. Winstein Department of Chemistry, Los Angeles,

University

California

of California

Id

90024

(Received 17 April 1967) One of the most interesting ethyl (VIII).

In hydrolysis,

to Spiro-alcohol

Pa

and instructive

I-OH containing a cyclopropane

in solvolysis

Spiro-anthranyl provided

by a solvolytic

of the anthrylethyl

(IV) instead of the Spiro-cyclopropane rate-enhancing

on ionization

rate.

of the Spiro-anthranyl

effects

Secondly,

ring.

Firstly,

of Spiro-cyclopropane,

solvolysis

with the 9-anthrylethyl

bridged ion V as regards

however,

the

carbonium

to compare

kinetic and thermodynamic

ion

this cation

product control.

example of “9-methyleneanthranyl-9-anthrylmethyl

Such tautomerism3

have been virtually forgotten by investigators Recently,

rates would disclose

H2, (CH3)2 and methylene groupings

benzyl type cation VII, and it is interesting

(e. g. , X Z= X9.

methylene group

in the methylene case (IV), the corresponding

Such a study would provide the simplest

could be

system (I) with the three analogs

is the 9-anthrylmethyl

tautomerism”

(VIII) or

It appeared to us that data of fundamental importance comparison

VIII-OH.

stable for direct observation 2b by nmr in S02-SbFS,

containing two hydrogen atoms (II), two methyl groups (III) or an olefinic

relative

is @-(9-anthryl)-

ring, along with the anthrylethanol

solvents from suitable derivatives

(I) types.

systems

kmetic product control from the bridged ion V leads mostly

The bridged ion V, which is sufficiently is generated

2-aryl-l-ethyl

.

was known long ago, but it appears to

between 1949 and nearly the present time.

Rergson and Flynn4 have carried

2475

out several

elegant studies in this field.

2176

~0.26

I-OAc

VIII-OH

CH2-CH2 OH

I-OH ET = 16.00@

19.320

ET=

17. XI p

ET=

ET=

18.810

ETA_=19.328

VI

II-OAc 24%

/ II-OH ET = 16.00/3 OAc

&IQ CH;

g$$)

Qgp

-CH3

CH20H

H’“H IV-OH

IlI-OAc

fin%

ET=

IV-OAc

18.818

AH H

ET=

20.26/3

/i

IX-OH

Er=

19.32p

NO.26

2477

Most recently,

4b

they have studied the acid-catalyzed

methyleneanthranols

(X;

favored anthrylmethyl chloride

R = CH3, C6H5;

ethyl ethers (XI;

conversion

of several

Y = OH) to the corresponding

R = CH3, C6H5;

substituted 9-

thermodynamically

Y = OEt) in ethanolic hydrogen

solution?C

XI x

@+Q&J ‘H

‘gHS Because of instability reactive

and general high reactivity,

esters we could manage and still compare The anthranyl acetate 5,6a II-OAc,

leaving group. analog’ tively,

C6H5R E ‘y

III-OAc,

mp 107”,

were prepared

using pyridine-acetic

the four systems mp 80-81’)

I-IV with the same

and the 9,9 -dimethylanthranyl

from anthranol and 9,9_dimethylanthranol,

anhydride at 0’.

The 9,9_dimethylanthranol5

was obtained by lithium aluminum hydride reduction of the corresponding anthranyl acetate”

6b I-OAc,

mp 62”,

were prepared from I-OH and IV-OH, -20”.

The 9-methyleneanthranol

hydride reduction Satisfactory

6d

respectively, mp 96-98”

first order solvolysis

were collected

The spiro-

acetate5 mp 89. S-90. So, 6c

at ca.

anhydride

(dec.),

by lithium aluminum

was prepared

a summary of the data being given in Table I.

and analyzed by nmr under conditions

From the Spiro-acetate

Spiro-alcohol

VIII-OH,

solvolysis of VIII-OTs

shown by control experiester III-OAc the

The unsubstituted anthranyl ester II-OAc formed

24% anthranol II-OH and 76% anthracene. I-OH and 16% anthrylethanol

The products of

containing added sodium

From the 9,9_dimethylanthranyl

anthranol III-OH was obtained.

previously from

ketone.

rate constants were obtained for the four acetateesters

ments to insure kinetic product control. corresponding

mp 79. S-80. So,

using pyridine-acetic

at 25” in 60% acetone (90% acetone in the case of I-OAc),

bicarbonate,

respec-

of the known 9-methyleneanthrone.

in aqueous acetone solvents, solvolysis

and the 9-methyleneanthranyl

IV-OH,

were the most

acetate derivatives

essentially

in aqueous dioxane2a

I-OAc was observed

84%

the same mixture observed

The 9methyleneanthranyl

ace-

2470

No.26

tate IV-OAc also led to a mixture, anthrylmethyl

alcohol

IX-OH.

was observed

from solvolysis

30% of methylene anthranol IV-OH and 7G% of the 9-

Essentially

the same mixture,

of the known 9-anthrylmethyl

28% IV-OH and 72% IX-OH, chloride7

TABLE I Summary of Solvolysis Solvent % Acetone

Acetate

Rates

Temp. “C.

I-OAc

90

25.0

II-OAc

60

25.0

Rel. Rate 2.5”

105k (set:‘) 113.8 k5.6

1150

38.2 f 0.7 1.00

II-OAc II-OAc

90 80

25. 25.0Oa

0.099 1.26kO.04

II-OAc

90

50.0

1.56 kO.03

II-OAc

90

75.0

18.46 + 0.41

III-OAc

60

25.0

42. 3 + 0. 4

1.09

60

25.0

46.7 + 0.2

1.22

IV-OAc

aExtrapolated

from data at higher temperatures

The rate data show the spiroanthranyl

ester I-OAc to be more reactive

parts II-OAc and III-OAc by three powers of ten? clopropane

ring in I-OAc provides

lease from the Spiro-“cyclopropane”

3

than its counter-

The great rate enhancement due to the cy-

a clear kinetic demonstration group in phenonium ions.

of the extensive

electron

This demonstration

is the

first of its kind, since this is the first time we have been able to approach kinetically ion such as V from a structure

which already incorporates

the cyclopropane

anthranyl I-OAc is also some three powers of ten more reactive analog IV-OAc,

providing

pane ring is greater

The new information provides

group.

not only confirmatory

evidence

The spiro-

effect of a cyclopro-

10

on kinetic product control 2a

a bridged

than the methylene anthranyl

another kind of example where the accelerating

than that of an olefinic

ring.

re-

in solvolysis

of I-OAc,

II-OAc and IV-OAc

on the behavior of the anthrylethyl

bridged ionV,

No.26

but

2479

also completely

cations

regarding

VI and VII during hydrolysis.

completely kinetic

new evidence

to yield anthracene

control,

only 76% of anthracene

in kinetic

control,

Thus,

disposed However,

towards

charge

at the CH: carbon

nucleophilic

gives 24% of anthranol

by proton loss.

center.

atom of the ArCHi

in kinetic

The anthrylmetbyl

control,

cation

yields a mixture

The anthrylmethyl

will be needed about other ArCHi factors

II-OH in

of water at the methyl group cationic

attack on the Ar group competitive

the partition

and 9-anthrylmethyl

ion VI, which loses a lo-proton

IX-OH in thermodynamic

70% from coordination

more information

best to correlate

control,

being formed

and 30% from water attack at the ClO-cationic tively low catiomc

of the anthranyl

the anthranyl

in thermodynamic

VII, which yields only anthrylmethanol products

partitioning

product

control

cation,

system,

of center

with its rela-

is obviously

favorably

with that at the CI-I; carbon. systems

before it is clear

with various

available

how

qheore-

tical parameters. REFERENCES 1. (a) Research supported in part by the National Science Foundation; (b) Research sponsored in part by the U. S. Army Research Office (Durham); (c) Postdoctoral Fellow of the FritzThyssen Foundation, KL)ln, Germany, 1965-1966; (d) Contribution # 2033. 2. (a) L. Eberson, J. P. Petrovitch, R. Baird, D. Dyckes and S. Winstein, E. 87, 3504 (1965); (b) L. Eberson and S. Winstein, ibid. 87, 3506 (1 F 5 . 3. (a) J. W. Cook, 1 Chem. Sot. 2798 (1928); (b) P. L. Julian, W. Cole, J. G. Schafer, J. Am. Chem. Sot. 7l, 2058 (1949). -

G. Diemer

and

4. (a) K. G. Flynn and G. Bergson, Acta Chem. Stand. l9_ 756 (1965); (b) G. Bergson and K. G. Flynn, Arkiv Kemi, in press; (c) Since the reaxion was followed by ultraviolet absorption, formation of any 9-methyleneanthranyl ether X by kinetic control was not observed. 5. This and the other indicated

new compounds

gave satisfactory

carbon

and hydrogen

analyses.

6. (a) Rapid transformation to anthracene occurs on melting; (b) Above the mp, a slow but complete transformation to VIII-OAc, mp 88-90°, occurs; (c) When acetylation of the Spiro-alcohol I-OH was performed at O”, a mixture of I-OAc (80%) and VIII-OAc (20%) was obtained; (d) Under many reaction conditions, the attempted lithium aluminum hydride reduction led mainly to 9 -methylanthracene. Using a 1.1 mole proportion of hydride, a very large volume of ether, and a 10 minute reaction period led to good results.

2u30

~0.26

7. Solvolysis of 9-anthrylmethyl chloride (and a-9-anthrylethyl chloride) has been previously studied by several investigators in correlating reactivity of ArCH2Cl and ArCHClCH3 with quantum mechanical quantities such as A Em of ionization8 Only 9-anthrylalkanol was observed as product, but no precautions were taken to insure kinetic product control. 8. See A. Streitwieser, Jr., “Molecular Orbital and Sons, Inc., New York, N. Y., 1961, pp. presentation of the rate data.

Theory for Organic Chemists”, 367-379, for pertinent references

John Wiley and a good

9. It is interesting to compare this rate ratio with the reported factors of 4 or 9 by which pcyclopropylcumyl chloride solvolyzes more rapidly than the p-isopropylcumyl analog in aqueous acetone or dioxane. L. B. Jones and V. K. Jones, Tetrahedron Letters No. 14 1493 (1966); H. C. Brown and J. D. Cleveland, J. Am. Chem. Sot. 88, 2051 (196r’ 10. The simple HMO T-electron energy change accompanying ionization (a En) is 1.45 p for IV-OAc, slightly greater than the value of 1. 30 /3 for II-OAc and III-OAc. However, the calculated advantage of IV-OAc is apparently balanced by such factors as inductive, hyperconjugative and solvation effects.