Chiral copper(II) complexes as Lewis acids for catalyzed cycloaddition, carbonyl addition, and conjugate addition reactions*

Bis(oxazoline) copper(II) complexes 1±3 function as enantioselective Lewis acid catalysts for carbocyclic and hetero Diels±Alder, aldol, Michael, ene, and amination reactions with substrates capable of chelation. X-ray crystallography of the catalyst reveals a propensity for the formation of distorted square planar or square pyramidal complexes. The sense of asymmetric induction is identical for all the processes catalyzed by [Cu((S,S)-t-Bu-box)](X)2 complexes 1 and 2 resulting from the intervention of a distorted square planar catalystsubstrate binary complex.