| 摘要 |
PURPOSE:To directly obtain the titled racemized compound rich in trans-isomer, in high efficiency on an industrial scale at a low cost, by using a brominated phosphorus compound as a racemization catalyst and racemizing optically active chrysanthemum monocarboxylic acids in the presence of an azo compound. CONSTITUTION:Optically active chrysanthemum monocarboxylic acids of formula (R is H, 1-20C alkyl, cycloalkyl or aralkyl; * represents asymmetric carbon atom) which are raw materials for pyrethroidal insecticides such as pyrethrin, allethrin, etc., useful as a low-toxic rapid-acting insecticide is racemized by reacting in the presence of a brominated phosphorus compound (e.g. phosphorus tribromide, phosphorus pentabromide, phosphorus oxybromide, etc.) and an azo compound (preferably azobisisobutyronitrile, etc.) preferably in an inert solvent such as benzene usually at 0-100 deg.C for several min-7hr. The process gives racemized optically active chrysanthemum monocarboxylic acids rich in trans-isomer and useful for the production of an insecticidal compound having higher activity. |
