Chiral Copper‐Semicorrin Complexes as Enantioselective Catalysts for the Cyclopropanation of Olefins by Diazo Compounds

Optical yields of up to 97% ee characterize the cyclopropanation of olefins with diazoacetates in the presence of the semicorrin complex CuL2 (R = CMe2OH). The chiral, C2-symmetrical semicorrin ligands LH are readily accessible in optically pure form from pyroglutamic acid as starting material.