| abstract |
The present invention relates to a process for the preparation of pyrethroid derivatives of general formula (I) for direct crystallization in high purity, wherein - A is chlorine or bromine or methyl - Y is hydrogen or fluorine - the wavy line denotes R or S configuration ( The cyanohydrin of formula (II) is acylated with an acid chloride of formula (III) and the cyanohydrin of formula (I) is reacted with benzaldehyde of formula (IV) by reaction with alkali cyanide and water, using amine as catalyst, such that alkali cyanide is 7- To a 9 mol% aqueous solution of benzaldehyde IV is added in the presence of 0.15 to 0.25 mol equivalents of amine per aldehyde, and the cyanohydrin of formula (II) formed in the reaction mixture is acylated in parallel with the formation of cyanohydrin. t fermentation: 8 pages (including Figure 2) HU 198 672 A -1- |