Asymmetric cyanoethoxycarbonylation of aldehydes catalyzed by heterobimetallic aluminum lithium bis(binaphthoxide) and cinchonine

Highly efficient catalytic asymmetric cyanoethoxycarbonylation of aldehydes was achieved by 10 mol% cinchonine with 10 mol% heterometallic (S)-aluminum lithium bis(binaphthoxide), which gave the cyanohydrins ethyl carbonates in excellent isolated yields (up to 99%) with moderate to high enantioselectivities (up to 95 % ee) under mild conditions (at -20°C). Especially, the solid aluminum lithium bis(binaphthoxide) free of tetrahydrofuran was obtained by a new procedure using (S)-bi(2-naphthol), aluminum isopropoxide and n-butyllithium in dichloromethane, which was insensitive to air and moisture and was very convenient to store and use. A catalytic cycle based on experimental phenomena was proposed to explain the nature of the asymmetric induction.