Racemic - production manner null of trance chrysanthemic acid

摘要

PURPOSE:To obtain the titled industrially excellent compound useful as a raw material for insecticides of pyrethroid type in high purity, by smoothly and efficiently converting a cis-chrysanthemumic acid derivative into a trans-form in the presence of both a silicon bromide compound and an azo compound. CONSTITUTION:A cis-form or a mixture of cis-form/trans-form of a chrysanthemumic acid derivative shown by the formula (X is Cl, Br or 2,2- dimethyl-3-isobutenylcyclo-propanecarboxyl) is made into a trans-form with a silicon bromide compound such as trimethylsilyl bromide and/or a phosphorus bromide compound such as PBr3 in the presence of a peroxide such as t-butyl hydroperoxide or an azo compound such as azobisisobutyronitrile in an inert organic solvent, preferably toluene for several minutes - 10hr to give a trans- chrysanthemumic acid derivative. The reaction temperature is -30-100 deg.C in the case of the acid halide and 50-140 deg.C in the case of the acid anhydride. The trans-form can produce various pyrethroids simply and in high yield.