Novel Thiourea-Based Bifunctional Organocatalysts and Their Applications in Asymmetric Catalysis

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Enantiomerically pure organic compounds are gaining continuously in importance. For example, more and more optically active Pharmaceuticals are introduced to the market, either as new drugs or as the result of a "racemic switch". Therefore, the development of asymmetric reactions that afford optically active compounds from simple and readily available reagents has been of ongoing interests over the past decade(s). Apart from metal-based asymmetric catalysis, small organic molecules-catalyzed enantioselective transformations have received increasing attention over the past years. In particular, organocatalysts bearing a thiourea (or urea) group are the subjects of intensive research. The double hydrogen-bonding interaction of the thiourea (or urea) NHs and the reactant has been generally realized to play the central role in (thio)urea-based catalysis. The incorporation of a second functional group has been another leap forward with regard to the scope of reactions amenable to (thio)urea catalysis. Great progress has been made in the design and applications of e.g. bifunctional thiourea-amine, or thiourea-alcohol catalysts.