Switching Enantioface Selection in the Asymmetric Nitro-Mannich Reaction Using PyBidine-Metal Catalysts

Arai and Matsumura have reported that a PyBidine-metal complex catalyzed a switchable enantiofacial selective asymmetric nitro-Mannich reaction of aldimines with nitromethane. The PyBidine-CoCl₂ complex catalyzed the reaction of N-Ts imines to give S-enriched adducts, while the PyBidine-Ni(OAc)₂ complex catalyzed the reaction of N-Boc imines to give R-enriched adducts. They suggest that PyBidine-metal catalysts produce the enantioselective adducts due to the switching enantioface selection based on the basicity and acidity of the metal salt in the catalyst. The enantiofacial switching using the same chiral ligand is interesting in asymmetric reactions.