Proline-based organocatalyst-mediated asymmetric aldol reaction of acetone with substituted aromatic aldehydes: an experimental and theoretical study

Abstract

This work involves a facile synthesis of three S -proline-based organocatalysts with C$_{2}$ symmetry and their effects in enantioselective aldol reaction of acetone with substituted aromatic aldehydes. Moderate enantioselectivities up to 61% ee were obtained depending on the nature of the substituents on the aryl ring. Computational calculations at HF/6-31 + G d level were employed to underline the enantioselectivity imposed by all the organocatalysts. Higher calculations at B3LYP/6-311 ++ G d,p scrf= solvent=dichloromethane //B3LYP/6-31 + G d levels of theory were also performed for the aldol reaction of acetone with benzaldehyde and 4-nitrobenzaldehyde catalyzed by 1. The computationaloutcomeswereconsistentwiththoseproducedbyexperimentalresultsandtheywerevaluabletoelucidate the mechanism for the observed stereoselectivity.