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.