Novel aminoimidazole derived proline organocatalysts for aldol reactions

A series of l-proline amides with 2-aminoimidazole have been synthesized and found to be highly efficient organocatalysts for aldol reactions when an appropriate acid was added to control and activate the acceptor carbonyl group. Under optimized reaction conditions, high yields (over 80%) and high selectivities (ee 98%, de 98/2) were obtained in intermolecular aldol reaction even with only 1 equiv of ketone. Likewise, these systems also can catalyze intramolecular aldol reactions with good results.