A safe and convenient new procedure for reducing aromatic compounds to birch-type products

Tetrahedron Letters,Vo1.25,No.20,pp Printed in Great Britain

2089-2092,1984

A SAFE AND CONVENIENT

NEW PROCEDURE

FOR REDUCING

COMPOUNDS

TO BIRCH-TYPE

PRODUCTS

Robert A. Benkeser,* Department

products

Aromatic

compounds

which are identical

Recently solvents

of Chemistry,

can be reduced

we' disclosed

that aromatic

calcium-amine obtained

by a calcium-amine-t-butyl by a Birch reduction

hydrocarbons

reductions

reductions

carried

First of all, calcium

procedure

below).

Likewise

has certain

out in liquid ammonia

ammonia.

calcium

can be used to reduce

cedures

which follow

advantages

in certain

amine

conditions,

the

which previously

were

over the sodium2 or lithium3

to large scale reductions

are relatively

high boiling

This is the first general

aromatic

ring systems

for the preparation

are typical

reaction

to products

in the presence

or amines

is much more amenable

1,4-cyclohexadiene

by calcium

of a proton source like

is much safer to handle than sodium or lithium

the amine solvents

than liquid

compounds

system to

(Table 1).

procedure

alcohols. calcium

are reduced

alcohol

of the same substrates.

We now wish to report that by varying

The calcium-amine-alcohol

manipulate

Purdue University

system can be used to reduce aromatic

by Birch-type

Rappa

Indiana 47907

to those obtained

to cyclic monoenes.

AROMATIC

James A. Laugal and Angela

W. Lafayette,

Abstract:

0040-4039/84 $3.00 + .OO 01984 Perqamon Press Ltd.

(see reduction and therefore

procedure

to Birch-type

employed

of p-xylene

much easier

ever developed

products.

for virtually

to

whereby

The detailed

of 1,4,5,8,9,10-hexahydroanthracene

of the methods

and hence the

pro-

and 1,4-dimethyl-

all the reductions

reported

in Table 1. An oven dried,

three-neck

500 mL round bottom flask was fitted with a Hershberg

gas inlet tube and an air-cooled upon calcium t-butyl

shot6

alcohol7

tected with mercury-mineral

Stirring

in the gray, viscous

action9

was started,

A mixture

of freshly

and, after 25 min the remaining

over a 25 min period.

mixture.

with an aqueous

usually

oil bubblers.

(4.45 g; 0.025 mol) and

All exits of the flask were prodistilled

n-butylamine

(38 mL),

(38 mL) and THF (90 mL) were added next and the flask was immersed

mol) was added dropwise

hydrolysis

The system was flushed with argon where-

sand (24 g), anthracene

(3.7 g; 0.05 mol) were added all at once,

dry8 ethylenediamine ice-bath.

Allihn condenser.

(4.0 g; 0.1 g at), white

stirrer,5

accompanied

similar to that described

Technical

solution

the hydrolysis elsewhere.la

alcohol

ether

(100 mL) was added followed

(27 g in 100 mL of H20).

step.

A yellow

2089

The remainder solid

in an

(11.1 g; 0.15

After 24 h only small pieces of calcium

diethyl

of NH4C1

t-butyl

remained

by cautious

A rather vigorous

of the work-up

was

(4.6 g; 100%) was obtained

re-

quite which was a

2090

Table 1.

Reduction

of Certain

Aromatic

Substrate

1.

Naphthalenea

2.

Tetralina

3.

Anthracenea

4.

Anisoleb

5.

o-Xyleneb

6.

m-Xyleneb

7.

p-Xyleneb

Compounds

Product

a

Composition

(81);

a)@);

(86);

a

(2);

a,,,

(3);

0

(7);

g(4)

gcH3

(6); GcH3

(13)

R1,

(90);

kH3

(5); kH3

(2)

a) The overall

yield was 90-95%.

the inevitable

loss of volatile

4

(11);

b) The overall

h

(1)

yield was 70-80%.

during work-up.

listed do not total lOO%, the remainder work was carried

4

(2)

CH3

CH3

products

9

(2)

(75);

(88);

(2)

m

(53

f

(2)

&cH3

$$

d) All analytical

(m

(33-34;

6

Procedure.

References

(16);

(6);

m76);

Alcohol

(%)c'd'e

a]

a

CH3

centaqes

by a Calcium-Amine-t-Butyl

The lower yields

were due to

c) In those cases where the per-

of the material

was of unknown

out on a Varian Model 3700 capillary

composition.

gas chromatograph.

When

e) The an Aeroqraph 200 instrument was used. 1 identity of each product was established either by a H NMR spectra (Perkin Elmer R-32 spectro13 C NMR (Varian XL-200 spectrometer operating at meter operating at 90 MHz in 5 mm tubes) or by samples were collected

for spectroscopic

50.3 mHz in 10 mm tubes). Proycki,

J.; Jablonski,

studies,

f) Hiickel W.; Schlee,

H. &em.

L. ROCZ. them. /9!3?,52, 1755.

J. Am. Chem. Sot. 1959, I__- 81, 3658.

Ber. 1955, 88, 346. h) Krapcho,

g) Mejer,

A. P.; Bothnerby-By,

S.; A. A.

2091

mixture cene

(GLPC analysis;

solid"

from petroleum melting

As described

maining

stirred12

column;

alcohol

rather

searchla

involving

abrasive

points

tightly

action

the presence

in connection

which

this combination

out at 0°C rather

a solvent mixture

be used to prevent

Analysis

the freezing

is an additional

(150 mL) and ethyl-

The mixture

by GLPC

advantage

seemed to afford

surface

was

distil-

(SE-30 capillary of 92% purity.

at all and the product

Contract

removes

depicted

which

form and

the use of a large exin this and previous

stirrer-sand coatings

technique.

from calcium

in Table 1 are much more

A wide variety

of other

selective

additive

of the substrate.

and THF along with the ethylene-

In all cases the ethylenediamine

Only in pure methylamine

did calcium

was very complex.

by the Department

of Energy of Basic Energy

DE-AC02-81ER10989.

(a) Benkeser,

R. A.; Belmonte,

(b) Benkeser,

R. A.; Kang J. ibid.

2.

Birch,

A. J. J.

3.

Wilds,

A. L.; Nelson,

4.

(a) Benkeser,

Chem.

SOC.

1944, _I__ 430.

N. A. J.

R. A.; Burrous,

AND NOTES

F. G.; Kang, J. J. Org.

H!V$,

See also Birch,

Am. Chem. Sot.

(b) Kwart, H. and Conley,

&em.

1983, _I__ 48, 2796.

A. J.

Quart. Rev.

44, 3737.

M. L.; Hazdra,

1953, __....

1950, ____ 4, 69.

75, 5360.

J. J.; Kaiser,

R. A. ibid.

can 16

later.

in that the ratio of the ethyl-

the solubility

for solubility.

distribution

substances

but these will be reported

to maximize

of the solvent mixture.

REFERENCES

reThe

Pure ethylenediamine freezes at 15 in the case of anthracene) (n-butylamine

of n-butylamine

This work was supported

along with sand for all coatings

encountered

effectively

of further

temperatures.

can be varied

ductions

28, 1094.

problems

to the "anti-freeze"

the best combination

that are worthy

necessitating

by the Hershberg

fluid at 0°C.

a mixture

stirrer

the insoluble

usually

obviated

provides,

remains

ingredient

under

removes

out of the ethylenediamine,

was an essential

Acknowledgment.

by calcium

the use of a Hershberg

of a second amine

and the other additives

proceed

with reductions

than at ambient

which

In the reduction of anthracene,

1.

flask

to stir for 40 min, the re-

of 1,4-dimethyl-1,4-cyclohexadiene

we have found that reductions

9°C and hence the presence

Sciences

as a

(24 g), p-xylene

After the usual workup,

at 140-2°C.

effectively

are completely

when carried

diamine

was allowed

We have found that all coating calcium

Secondly,

There

boiling

to the calcium

surfaces.14

enediamine

sand

in a 1 L three-neck

n-Butylamine

with argon.

this mixture

time a gray solid developed.

This combination

cess of the metal.

provides

(12.0 g; 0.3 g at), white

(39.5 g; 0.534 mol) was added over a 40 min period. which

product

was confirmed l3 by 'H and 13C NMR.

reductions.

which adhere

2.9 g (63%) of the desired

147-148°C.

and flushed

First of all, we now recommend

comment.

Recrystallization

(6%) and 2% anthracene.

yielded

(4.9 g; 0.066 mol) were placed

13.6 g (63%) of material

There are several

about

60 m x 0.25 mm) of 1,4,5,8,9,10-hexahydroanthra-

calcium

After

60 m x 0.25 mm) indicated

The structure

calcium

oven-dried

for 24 h, during

lation yielded

lit."

alcohol

(150 mL) were added.

t-butyl

(30-60°C)

at 146-147°C;

had been previously

enediamine

ether

above for anthracene,

(21.2 g; 0.2 mol) and t-butyl which

column;

(76%), 1,2,3,4,5,6,7,8,9,10-decahydroanthracene

of the mixture white

SE-30 capillary

1923,

38,

E. M. J.

2011.

Org. Chem. 1963, ____

re-

2092

5.

(a) Hershberg, Org. Synth.

E. B. Ind. Eng. C&m..

AnaZ.

Co/Z. vo2. 11, 1943, ___- 116.

1936, 1_-1 8, 313.

Ed.

The Hershberg

had only one glass ring and one strand of Chromel-20

(b) Pinkney,

P. S.

stirrer we used in this work gauge wire as pictured

on p. 117

of ref. 5b.

6.

Ca shot

7.

Very likely other

(99.5%)

purchased

are in the process 8.

We have found

from Alfa Products

alcohols

of screening

the drying

I. J.

Org.

work

this way, there may be induction before

some of the reductions

of moisture

or HCO;.

stirred over fresh

We now recommend

before a final distillation. the induction 9. 10.

11. 12.

14.

6 2.39

6 30.5, 35.92,

123.4, 124.5.'

Runge,

V. J. J.

Chem.

Prak.

the mixture

complete

type) laboratory

6 1.65

stirrer.

(Aldrich,

99+%)

be

for 3 h over CaO eliminates

(s, 8 H), 5.7 (s, 4 H).

continued

by a Hershberg

(s, 4 H), 5.4 (broad s, 2 H).

out an experiment

0.025 mol

for 4.5 h.

of ethylenediamine cept for anthracene

0.25 g at (10 g) of

50% of the calcium

between

was withdrawn

sand was added.

and n-butylamine.

is used alone,

After an additional

This mixture

(Received in USA 6 February 1984)

only

was re24 h of

no reduction

occurs.

Thus,

in 75 mL of n-butyl-

unchanged.

The usual

where THF was also added.

stirrer

was obtained.

was recovered

Rappa.

and

20 h of stirring,

was stirred with 0.125 g at of calcium

by Miss Angela

the calcium

was added and the

and was shown by GLPC

After an additional

and white

(paddle-

was used up

The latter was very likely the reaction

At this point the mechanical

had formed.

for 4 days, 88% of the p-xylene studies

in which

(2.7 g) of p-xylene

An aliquot

that when n-butylamine

when 0.025 mol of p-xylene

complete the

13C NMR

for 19 h using an ordinary

from a direct

a 62% yield of 1,4-dimethylcyclohexene

We have ascertained

was virtually

(Table 1, entry 6) where

in the solution.

resulting

stirrer

13C NMR (CDC13,

131.2.

3% of 1,4-dimethylcyclohexene.

Unpublished

to hours

to the presence

dried this way virtually

At this time approximately

To this slurry,

9% of the latter compound

16.

(s, 6 H), 2.54

had formed

formation

ethylenediamine.

amine

that the ethylenediamine

in 75 mL of ethylenediamine

and a gray precipitate result of amide

15.

this problem

after 11 h.

this point, we carried

was stirred

stirring,

it is dried

of minutes

to stir for 24 h, the reaction

To demonstrate

placed

When

R. A.;

32, 280.

lL366,

6 23.1, 73.0, 118.6,

was

Drying over

here.

(CDC13, Me4Si)

stirring

We have traced

(s, 4 H), 2.52

was allowed

was virtually

to contain

from a matter

This was also true for m-xylene

'H NMR (CDCl3, Me4Si)

calcium

varying

Using ethylenediamine

'H NMR (CDCl 3, Me4Si)

at the end of 7 h.

13.

We

periods.

Me4Si)

reduction

point.

for at least 24 h and then refluxed

The use of an ice bath is recommended

Although

alcohol.

L.; Friedel,

is not the best procedure.

periods

will start.

NaOH pellets

to be a very critical

(ref. 1; see also Reggel,

1957, 1--_ 22, 891)

Chem.

to t-butyl

other alcohols.

of ethylenediamine

sodium as we did in our earlier Wender,

was used.

will work or may even be superior

solvent

system consists

was used for all cases

of a mixture

in Table 1 ex-