ASYMMETRIC SYNTHESIS OF CYCLOPROPANE CARBOXYLATES: CATALYSIS OF DIAZOACETATE REACTIONS BY COPPER(II) SCHIFF BASE COMPLEXES DERIVED FROM α-AMINO ACIDS

Article abstract of DOI:10.1016/0022-328X(84)80341-1

The asymmetric synthesis of cyclopropane carboxylates, which are intermediates in the synthesis of photostable pyrethroid insecticides, by catalysed reaction of ethyl dizaoacetate with halo-olefins is described.Using chiral copper(II) Schiff base complexes derived from L-phenylalanine and aromatic aldehydes as catalysts, both the degree and direction of optical induction were found to depend upon the olefin.Unexpectedly, in several reactions there was marked stereoselectivity at C(3), rather than C(1), of the cyclopropanes.This novel pattern of selectivity is interpreted in terms of carbene transfer from a metal-carbene intermediate in which a chiral ligand controls the orientation of an approaching olefin.