Tetrahedron Asymmetry p. 1043 - 1049 (1998)
Update date:2022-08-23
Topics:
Roos, Juergen
Stelzer, Uwe
Effenberger, Franz
A technical scale preparation of optically active (1R,cis, αS)- cypermethrine 4 from racemic m-phenoxybenzaldehyde cyanohydrin acetate (RS)- 1 and (1R,cis)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-carboxylic acid chloride (1R,cis)-3 is described. Key steps of the new procedure are a lipase catalyzed enantioselective transesterification of (RS)-1 with n-butanol and direct acylation of the mixture of (R)-1 and (S)-cyanohydrin (S)-2 with (1R,cis)-3 to give enantiomerically pure (1R,cis,αS)-4. The unchanged (R)-1 is removed from (1R,cis,αS)-4 by distillation, and is racemized with triethylamine to give (RS)-1 which is returned to the process. The total yield of (1R,cis,αS)-4 referred to (RS)-1 is 80%.
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