Highly Enantioselective Biginelli Reaction Promoted by Chiral Bifunctional Primary Amine‐Thiourea Catalysts: Asymmetric Synthesis of Dihydropyrimidines

The diastereospecific formation of dihydropyrimidines (DHPMs) has been achieved in moderate to high yields with up to 99% ee by a Biginelli reaction. The reaction was performed by using a combined catalyst consisting of a chiral bifunctional primary amine-thiourea 9f and a Bronsted acid with tert-butylammonium trifluoroacetate (t-BuNH 2· TFA) as additive in dichloromethane at room temperature. The possible mechanism for the reaction has been proposed to explain the origin of the activation and the asymmetric induction.