Synthesis of chiral pentacyclo-undecane ligands and their use in the enantioselective alkylation of benzaldehyde with diethylzinc

Abstract

The synthesis of a new class of chiral pentacycloundecane cage annulated bidentate ligands is reported. This class of ligands can be used in many reactions that are catalysed by amino alcohol ligands. The ability of the chiral ligands to asymmetrically catalyse the reaction between diethylzinc and benzaldehyde was investigated. The cage annulated bidentate ligands have C 1 symmetry and showed poor to good enantioselectivity with high yields compared to previous systems reported using other amino alcohol ligands. An important conclusion from the results is that both ligands should be involved in the mechanism as the bidentate ligands gives much improved enantioselectivity when compared with a single chiral source molecule. This system could be utilised as a versatile probe for examining the reaction mechanism.