C - Chemistry – Metallurgy – 07 – C
Patent
C - Chemistry, Metallurgy
07
C
260/479.8
C07C 255/53 (2006.01)
Patent
CA 1162560
K 1813 ABSTRACT Process for preparing cyclopropane carboxylic acid ester derivatives This invention relates to the preparation of cyclopropane carboxylic acid ester derivatives, which are useful as pesticides. There is provided a process for preparing a 1:1 mixture of 1R cis S- and 1S cis R- isomers substantially free of 1S cis S- and 1R cis R- isomers of a compound of formula: Image (I) wherein R1 and R2 are each independently selected from chlorine, bromine and methyl, which process comprises dissolving a mixture of 1S cis S- and 1R cis R- isomers of the compound of formula I, alone or in the presence of 1R cis S- and 1S cis R-isomers, in organic amine base containing from 5 to 7 carbon atoms and being a secondary amine containing two branched alkyl groups or a tertiary amine, and crystallising out from the resulting solution of cis - isomers of formula I in the organic amine base a 1:1 mixture of the 1R cis S- and 1S cis R- isomers substantially free of 1S cis S- and 1R cis R- isomers. The process of the invention yields a product which contains substantially twice as much of the most active isomer of the compound of formula I as a racemic mixture of all four cis - isomers, and is a readily effected process which does not involve any asymmetric synthesis or optical resolution steps.
372649
Mason Ronald F.
Wood Derek A.
Shell Canada Limited
Smart & Biggar
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