PROCESS FOR THE PREPARATION OF CERTAIN PAIRS OF ENANTIOMERS OF (-CYANO-3-PHENOXY-4-FLUOROBENZYL PEREMETHRATE

摘要

A process for the preparation of a mixture principally comprising the (b) 1R-3R- alpha S+1S-3S- alpha and (d) 1R-3S- alpha S+1S-3R- alpha R enantiomers of the compound alpha -cyano-3-phenoxy-4-fluorobenzyl permethrate, comprising dissolving a mixture of all 8 stereoisomers of the compound alpha -cyano-3-phenoxy-4-fluorobenzyl permethrate in an alcohol having 2 to 4 carbon atoms, adding a secondary or tertiary alkyl amine having 2-6 carbon atoms in each alkyl moiety and allowing the mass to crystallize, whereby the desired mixture of enantiomers b) and d) crystallizes out of the solution.