Unexpected efficiency of non-C(2) -symmetric bis(hydroxyamide)-based zinc-chelate catalysts.

Asymmetric bis(hydroxyamide)-based zinc-chelate catalysts are able to promote the enantioselective addition of diethylzinc to benzaldehyde in the absence of titanium with yields and ees comparable, or inclusively superior, to their C(2) -symmetric analogues. This unexpected fact demonstrates that the previously established assumption on the necessity of using C(2) -symmetric bis(hydrdoxyamides) to generate C(2) -symmetric zinc-chelate catalysts can be discarded, which expand the possibilities for designing new ligands based on the interesting hydroxyl-amide functional grouping.