Highly Enantioselective Zinc/Amino Alcohol-Catalyzed Alkynylation of Aldehydes

A highly enantioselective and practical alkynylation of aldehydes catalyzed by a cyclopropane-based amino alcohol zinc catalytic system was reported. The results show that in the absence of dimethoxypolyethylene glycol (DiMPEG), 10 mol% of amino alcohol ligand catalyzed the reaction at 20° to give the highly optically active esters. An increase in catalyst loading to 20 mol% results in an improvement of the reaction yield at 0°C by 66%, while the ee value remains high at 92%. The catalytic system is found to exhibit excellent enantioselectivity in the asymmetric reaction of methyl propiolate with aldehydes. The amino alcohol ligand with zinc is the most effective system reported for the asymmetric addition of alkynylzinc to aromatic aldehydes. The optically active cyclopropane derivative with its special structural configuration is found to be a good chiral ligand unit for asymmetric catalytic reactions.