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J Org Chem. 2002 Jun 28;67(13):4615-8.

A new protocol for a regioselective aldol condensation as an alternative convenient synthesis of beta-ketols and alpha,beta-unsaturated ketones.

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1
Vioryl S.A. Research Department, Kato Kifissia, 14564 Athens, Greece.

Abstract

A general and convenient synthesis of beta-ketols and alpha,beta-alkenones has been achieved by a Knoevenagel condensation of a beta-ketoacid with an aldehyde in aqueous medium. Saponification of a beta-ketoester by an aqueous KOH 10% solution gives the potassium salt of the beta-ketoacid, which is condensed in situ with an aldehyde at pH 7.8-8.0, at 60 degrees C for 5-6 h. The intermediate beta-ketocarboxylate is smoothly decarboxylated in the reaction medium, giving the beta-ketol in high yield (75-90%). Acidification of the reaction mixture at pH 1 and heating at 70 degrees C under vigorous stirring for 6 h, leads directly to the corresponding alpha,beta-unsaturated ketone in good yield (65-75%).

PMID:
12076169
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