Nickel-coordinated chiral enols and Michael addition intermediate stabilized by the Ni–C bond

A representative within a new class of chiral enol Ni II complexes derived from a Schiff base of aminoacetone and ( S )-2- N -( N -benzylprolinoylamino)benzophenone was prepared, and its performance in nucleophilic addition was estimated. The complex was inert towards aldehydes and activated C=C bonds but reacted with carboxylic anhydrides and di- tert -butyl acetylenedicarboxylate. An unusual Michael addition intermediate stabilized by the Ni–C bond was discovered in the latter reaction.