Enantioselective Catalysis with Metal Complexes Containing Heterocyclic Ligands

Chiral C2‐symmetric semicorrins, a class of bidentate nitrogen ligands, are readily prepared in enantiomerically pure form starting either from D‐ or L‐pyroglutamic acid. They possess a number of features that make them attractive ligands for enantioselective control of metal‐catalyzed reactions. (Semicorrinato)copper complexes have been used as efficient catalysts for the enantioselective cyclopropanation of olefins with diazo compounds. Using (semicorrinato)cobalt complexes as catalysts, α,β‐unsaturated carboxylic esters and amides can be enantioselectively reduced with sodium borohydride, giving the corresponding saturated esters and amides with enantiomeric excesses up to 98%.