Experimental and Theoretical Studies in Hydrogen-Bonding Organocatalysis

Abstract: Chiral thioureas and squaramides are among the most prominent hydrogen-bond bifunctional organocatalysts now extensively used for various transformations, including aldol, Michael, Mannich and Diel s-Alder reactions. More impo rtantly, the experimental and computational study of the mode of activation has begun to attract considerable attention. Various experimental, spectroscopic and calcula tion methods are now frequently used, often as an integrated approach, to establish the reaction mechanism, the mode of activation or explain the stereochemical outcome of the reaction. This article comprises several case studies, sorted according to the method used in their study. The aim of this review is to give the investigators an overview of the methods currently utilized for mechanis tic investigations in hydrogen-bonding organocatalysis. Keywords: organocatalysis; hydrogen bonding; thiourea; squaramide; experimental and computational studies; reaction mechanisms 1. Introduction