Decarboxylative elimination: A new method for the synthesis of α,β-unsaturated ketones

Tetrahedyon Letters No. 75, up 1321 - 1322. @Pergmon Press Ltc. 1979. Printed in Great Britain.

DECARBOXYLATIVE A NEW METHOD

ELIMINATION:

FOR THE SYNTHESIS

OF a,B-UNSATURATED

KETONES

Vichai ReutrakulA, Surachai NimgirawathB, Sirichai PanichanunA and Yupayao SrikirinA A Department of Chemistry, Faculty of Science, Mahidol University Rama VI Road, Bangkok 4, Thailand BDepartment

of Chemistry,

Faculty of Science,

Nakorn

An efficient decarboxylative

one-pot

University,

Pathom, Thailand

synthesis

elimination

Silapakorn

of cl,B-unsaturated ketones via the

of sodium glycidates

with lead tetraacetate

is described.

The transformation

of a carboxylic

acid (or derivative)

one carbon atom has been a subject of considerable decarboxylation ketones2

reaction which

from the corresponding

is highly convenient carbonyl

compounds

interestI.

to ketone with a loss of

We wish to report a novel

for the synthesis (equation

of o,B-unsaturated

1). 0

R R1

R

> >" R2

The process acetate, indicated

followed

(1)

1

>" R2

involves

the decarboxylation

by the pyrolytic

in equation

elimination4

of sodium glycidate3

of the cl-acetoxyketone

_I_with

intermediate

(2).

2, R = -CH8(90% c, R = E-Pr-(90%

yield); b, R = -CH2CH3(94%

yield);

yield); d, R = n-pentyl-(80%

e, R = n-hexyl-(82%

yield).

lead tetra-

yield);

1. as

1522 No. l'j

The following mole), stirred

pyridine

procedure

(0.02 mole),

under nitrogen

was decomposed

thick layer chromatography

Rf = 0.6) to give &

of sodium glycidate

(0.02 mole) and dry benzene

with ethylene

(100 ml) was

before being refluxed glycol.

-le (0.01

for 5 hr.

The product was purified

(Merck PF254 silica gel; 7:3 chloroform-light

by

petroleum;

in 82% yield.

The overall an acyl and a double as a masked

lead tetraacetate

a mixture

for 0.5 hr at room temperature,

Excess lead tetraacetate preparative

is representative:

process

represented

bond at the original

nucleophilic

by equation carbon.

(1) involves

the introduction

The C-2 atom of the a-haloester

of both functions

acyl carbon4.

0

,'C02R3 R-CH

We are presently

=

\

R-v=

X

exploring

the scope and limitation

of this reaction.

REFERENCES 1.

B.M. Trost, Chem. Rev., 78=, 363 (1978).

2.

For recent reports M. Montury

see:

and J. Gore, Tetrahedron

M. Charpentier-Morize 3.

All sodium

L.J.

. 5.

glycidate

For pyrolysis 8&

salts were'prepared

J. Org. Chem., 2, of glycidic

Bull. Sot. Chim. Fr., 331 (1977). by known procedures:

W.S. Johnson,

(1953); J.A. Waters

J.S. Belew, and B.

3232 (1971). esters see:

E.P. Blanchard

Jr. and G. Bichi, J. Amer. Chem. Sot.

955 (1963).

O.W. Lever, Jr., Tetrahedron, J. Org. Chem., 2,

Chem. Comn., 633 (1975);

Lett., 219 (1977);

and J. Sansoulet,

Chinn and R.H. Hunt, J. Amer. Chem. Sot., 75_, 4995

Witkop, 4.

I. Fleming and A. Pearce, J.C.S.

450 (1978).

32_, 1943 (1976); G. Stork, A.Y.W.

Leong and A.M. Touzin,

4l_, 3491 (1976); R. Lohmar and W. Steglich, Angew. Chem. Int.

Ed. Engl.,