Synthesis of unsaturated 5-hydroxy- and 7-oxo-acids by addition of unsaturated carboxylic acid dienolates to carbonyl compounds

Abstract

Alkylation of dienolates derived from crotonic and dimethylacrylic acids (2) by saturated or aromatic aldehydes and ketones (1) at low temperature affords 2-substituted-3-hydroxy-acids (3). The dianionic species of these isomerize on heating to (E)- and (Z)-unsaturated-5-hydroxy-acids (4) and (5), for crotonic and dimethylacrylic acids, respectively. Unsaturated ketones (6) suffer 1,4-addition through γ-alkylation, leading to (E)-unsaturated-7-oxo-acids (8) for both crotonic and dimethylacrylic acids. Unsaturated 5-hydroxy- and 7-oxo-carboxylic acids are readily prepared by the procedure here established.