Tetracyanoethylene as an aromatizing agent

Tetracyanoethylene as an aromatizing agent

TetrahedronLetters No. 5, pp. 205-207, 1962. in Great Britain. Pergamon Press Ltd. Printed TETRACYANOETHYLENE AS AN ARWTIZING AGENT Daniel T. Long...

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TetrahedronLetters No. 5, pp. 205-207, 1962. in Great Britain.

Pergamon Press Ltd. Printed

TETRACYANOETHYLENE AS AN ARWTIZING

AGENT

Daniel T. Longone and Gary L. Smith Department of Chemistry,The University of Michigan Ann Arbor, Michigan (Received19 February 1962)

TETRACYANOETHYLENE(TCNE) has proven to be an extremelyversatile chemical 1 intermediate. The reactions of TCNE with conjugateddienes have been well 293 with conjugated delineated. In contrast to normal Diels-Alderadductions 4-6 acyclic and cisoid cyclic dienes, Spiro-compounds are generatedby cycloaddition of TCNE to the exocyclicdouble bond in transoidmethylenecycloalkenes. Less commonly,the cycloadditionof TCNE to an endocyclicdouble 5 bond can yield a bicyclohexanederivative. Supplementingits reactions with conjugateddienes we wish to report that TCNE functionsas an efficient hydrogen acceptor in the aromatizationof certain non-conjugatedcycloalkadienes. The facile addition'of TCNE to norbornadieneto give the homo-DielsAlder adduct I led us to investigatethe reactionsof TCNE with other nonconjugateddienes. In an attempt7 to generate the tricylodctanederivative II, a solution containingequimolar amounts of 1,4-cyclohexadiene and TCNE

1

T.L. Cairns det al

J. Amer. Chem. Sot. a,

2775 (1958).

W.J. Middleton,R.E. Heckert, E.L. Little and C.G. Krespan, J. Amer. Chem. Sot. & 2783 (1958). -_' 3 A.T. Blomquistand Y.C. Meinwald, J. Amer. Chem. Sot. &, 3619 (1960). A.T. Blomquist and Y.C. Meinwald, J. Amer. Chem. Sot. g, J.K. Williams, J. Amer. Chem. Sot. a,

667 (1959).

4013 (1959).

D.S. Matteson, J.J. Drysdale and W.H. Sharkey, J. Amer. Chem. Sot. g, 2853 (1960). We are indebted to Dr. P. Scheiner for carrying out this reaction. 205

206

in

Tetracyanoethylene

benzene-dioxane

product,

(3r2)

separated

was

from

the

as

refluxed cooled

an aromatizing

for

agent

30 min.

reaction

No.5

A white

mixture,

had

crystalline m.p.

solid,

from

formed

(TCNA) , identified direct

of

by the

its

reduction

functioned

as

confirmed8

by repetition

solvent. crude

TCNA and

particularly ;ldiene

a hydrogen

After

and

benzene. reaction

TCNE. in

dioxane

176’)

‘no evidence

for

of

and the

C,

spectrum

TCNE with

acceptor of

mild

TCNA (dec.

infrared

the

in

time

94% benzene. isomerization

that

of

Under the

the

the

can

three

sample

diene

was

of its

as

afforded

98%

be effected of

days

by

TCNE

system

amounts

to

and

dimethylformamide

a variety diene

N, 42.92)

That

aromatization

for

This

an authentic

of

purified

temperature 10

of

iodide.2

equimolar

187’.

be tetracyanoethane

H, 1.38;

of 4 hr,

The above

room

dec.

aromatization in

conditions: at

55.18;

hydrogen the

gave to

with

reaction

reflux 10

(312) proved

(Found:

an arbitrary 9%

acetate

quantitatively,

by analysis

comparison

prepared

II

benzene-ethyl

essentially

(dec.);

_

r recrystallization

185-190’

under

1,4-cyclohexagive

reaction

conjugated

98% crude conditions, isomer

is

observed.”

8

Dr. B.C. McKusick of the du Pont Co. has has observed the formation of TCNA, m.p. reaction of TCNE and 1,4-cyclohexadiene.

informed his _< laboratory _ __n, us that 184-188’ (see ref. 9), from the

9 The decomposition temperature of TCNA varies markedly with sample Reproducible results can be obtained by purity and heating time. introducing the sample into the heating bath at 170’. The previously reported (ref. 2) decomposition temperature can be raised by ca. 20’ by this technique. 10 Determined spectrophotometrically (ultraviolet) utilizing the distillate from the reaction filtrate and appropriate controls. 11 TCNE and 1,3-cyclohexadiene readily give a Diels-Alder adduct in high yield (ref. 2).

No.5

Tetracyanoethylene

In

a similar

aromatized gives

to

5a

naphthalene

Utilizing genation

(6C$,

an excess

mole)

latter

compound

dioxane)

207

1,4-dihydronaphthalene

recrystallized)

of TCNE it

diene

solution

(0.031

in

agent

and

is

2,5_dihydrobenzoic

acid

acid.

a reactive

A dioxane

an aromatizing

(4 hr reflux

manner

benzoic

as

after was

which

(100

ml)

6 hr

reflux

is

possible

subsequently

to

generate

undergoes

Diels-Alder

of g,lO-dihydroanthracene

identified

by dehydro-

(0.010

affords.

in 4%

yield,

by m.p.,

mixed-m.p.,

the and

adduction.

mole)

adduct

and

TCNE

III.

comparison

The of

its

a:;

m infrared This

spectrum example

adduction It

indicates

as

a structure

appears

that

aromatization conditions, thene,

with

of

that

of

that

caution

probe TCNE is

authentic

III

must

in

is

9,10-dihydrophenanthrene,

normal

manner.

in utilizing

dehydrogenating Under

between tetralin,

the

TCNE

systems.

an effective

observed

in

be exercised

polycyclic

1,4-dihydrobenzenoids.

no reaction

prepared

agent

a variety

TCNE and

of

in

the

experimental

cyclohexene,

ethylbenzene,

only

bibenzyl

acenaphand

1,5-cyclodctadiene. Acknowledgement - This Research Office (Durham).

research

was

supported

in

part

by the

U.S.

Army

2