Process for the preparation of certain enantiomeric pairs of .alpha.-cyano-3-phenoxy-4-fluoro-benzyl permethrate
AssigneeBayer Aktiengesellschaft
InventorsRainer Fuchs, Klaus Naumann
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Abstract
A process for the preparation of the enantiomeric pairs (1R-3R-.alpha.S+1S-3S-.alpha.R) and (1R-3S-.alpha.S+1S-3R-.alpha.R) from a mixture of all 8 stereoisomers of the compound .alpha.R/S-cyano-3-phenoxy-4-fluorobenzyl 3R/S-(2,2-dichlorovinyl)-2,2-dimethyl-1R/S-cyclopropanecarboxylate, comprising dissolving the mixture in a secondary or tertiary alkylamine having 2-6 C atoms per alkyl radical, subjecting the solution to crystallization whereby the enantiomeric pairs (1R-3R-.alpha.S+1S-3S-.alpha.R) and (1R-3S-.alpha.S+1S-3R-.alpha.R) crystallize out from the solution, and separating the crystallized material. The crystals are enriched in the most active components.
Claims3
A process for the preparation of the enantiomeric pairs (1R-3R-.alpha.S+1S-3S-.alpha.R) and (1R-3S-.alpha.S+1S-3R-.alpha.R) from a mixture of all 8 stereoisomers of the compound .alpha.R/S-cyano-3-phenoxy-4-fluorobenzyl 3R/S-(2,2-dichlorovinyl)-2,2-dimethyl-1R/S-cyclopropanecarboxylate, comprising dissolving the mixture in a secondary or tertiary alkylamine having 2-6 C atoms per alkyl radical, subjecting the solution to crystallizaztion whereby the enantiomeric pairs (1R-3R-.alpha.S+1S-3S-.alpha.R) and (1R-3S-.alpha.S+1S-3R-.alpha.R) crystallize out from the solution, and separating the crystallized material.
Dependencies are inferred from the claim text.