PRODUCTION OF RACEMIC CHRYSANTHEMUM-MONOCABOXYLIC ACIDS

PURPOSE:To efficiently obtain the objective compounds in the same manner as that in the case of a coexisting assistant, such as peroxide or azo compound, by the coexistence of a specific amount of oxygen in a reaction system for reacting optically active chrysanthemum-monocarboxylic acids with hydrogen bromide and producing the corresponding racemic modification. CONSTITUTION:Optically active chrysanthemum-monocarboxylic acids expressed by the formula (R is H, 1-20C alkyl, cycloalkyl or aralkyl; * indicates asymmetric carbon) are reacted with hydrogen bromide to provide the corresponding racemic modification. In the process, the above-mentioned reaction is carried out in the presence of oxygen and the total molar amount of the oxygen is simultaneously >=1/70, preferably (1/150)-(1/2) based on the chrysanthemum- monocarboxylic acids. Thereby, the objective compounds useful as a raw material for pyrethroid-based insecticides are industrially and advantageously obtained. Not only the hydrogen bromide which is normally used as an industrial raw material and readily handleable for moisture, etc., can be utilized but also inexpensive and easily handleable oxygen or air can be used in place of the afore-mentioned assistant by the above-mentioned method.