L-Proline Derived Secondary Aminothiourea Organocatalyst for Synthesis of Coumarin Derived Trisubstituted Methanes: Rate Enhancement by Bifunctional Catalyst over Cooperative Catalysis

Abstract

Although l-proline derived aminothioureas are being used as catalyst in asymmetric synthesis, their applications in multicomponent reactions are not yet reported in the literature. We report herein a l-proline derived secondary aminothiourea as a multifunctional catalyst in multicomponent reaction for synthesis of coumarin-based unsymmetrical trisubstituted methanes whose prototype has been found to be acetylcholinesterase inhibitor. The method requires low catalyst loading (5 mol%), very short reaction time (15–30 min) to give excellent yields. For the first time, it is observed that our bifunctional catalyst significantly increases the rate of conversion in comparison to that of two cooperative organocatalysts having similar catalytic sites. l-Proline derived secondary aminothiourea organocatalyst in multicomponent reaction: synthesis of coumarin derived trisubstituted methanes