Copper(I)/SaBOX catalyzed highly diastereo- and enantio-selective cyclopropanation of cis-1,2-disubstituted olefins with α-nitrodiazoacetates

A copper-catalyzed highly stereoselective cyclopropanation of 1,2-disubstituted olefins with α-nitro-diazo acetates has been developed, giving the desired products in up to 97% yields, up to >99/1 dr and up to 98% ee, which provides an efficient access to the synthesis of optical active cyclopropane α-amino acids and unnatural α-amino acid derivatives.