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

A representative within a new class of chiral enol NiII 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.