2-Dihalovinyl 3,3-dimethyl cyclopropane carboxylates prodn. - by base catalysed cyclisation of new polyhalo dimethyl hexanoyl halides (NL181176)

摘要

Process for preparing cyclopropane derivs. of formula (I) comprises treating acid halides (II) with base; (X = Cl or Br; R' = 1-4C alkyl; Y and Z are each Cl or Br; R is CX2=CH- in which case 2 equivs. base are used or CX3CH2- in which case 3 equivs. base are used), =1 equiv. of base in as alkali alkoxide derived from R'OH and the process is carried out in sequential stages with alkoxide treatment as the first or second stage, when it is second stage the base used in the first stage is a tert. amine. (II) are new cpds. (I) (as the free acid) are intermediates for insecticides such as 3-phenoxybenzyl 2-(2,2-dichlorovinyl)3,3-dimethylcyclopropane carbodylate. The process provides (I) without use of the explosive and carcinogenic ethyl diazoacetate required in the known method.