Enantioselective Conjugate Addition of Diethylzinc to Chalcones Catalysed by Chiral Ni(II) Aminoalcohol Complexes

Conjugate addition of diethylzinc to chalcones is catalysed by complexes prepared in situ from Ni(acac)2 and cis-exo-N,N-dialkyl-3-aminoisoborneols or (+)-cis-endo-N,N-dimethyl-3-aminoborneol ((+)-DAB) (13b). The products are obtained with enantioselectivities up to 84 %. When scalemic (-)-cis-exo-N,N-dimethyl-3-aminoisoborneol ((-)-DAIB) (3c) was employed in the reaction a positive nonlinear relationship was found. Several factors which govern catalyst activity and enantioselectivity have been investigated