RACEMIZATION OF OPTICALLY ACTIVE CHRYSANTHEMUM-MONOCARBOXYLIC ACIDS

摘要

PURPOSE:To proceed racemization efficiently and to obtain racemic modification rich in trans form suitable for a raw material for pyrethroid type insecticides, by treating an optically active chrysanthemum-monocarboxylic acid with hydrogen bromide especially in the presence of a peroxide or an azo compound. CONSTITUTION:An optically active chrysanthemum-monocarboxylic acid [especially effective for use (-) form carboxylic acid or carboxylic acid rich in (-) form] shown by the formula (R is H, 1-20C alkyl, cycloalkyl or aralkyl; *is asymmetric carbon) is treated with hydrogen bromide or further preferably treated with hydrogen bromide in the presence of a peroxide (e.g. hydroperoxide) or an azo compound (e.g. azonitrile) to give an optically active chrysanthemum- monocarboxylic acid [especially compound of trans form rich in (+) form)]. Readily handleable hydrogen bromide is usable and this process is industrial and advantageous.