Regioselective Brønsted Acid-Catalyzed Annulation of Cyclopropane Aldehydes with '-Aryl Anthranil Hydrazides: Domino Construction of Tetrahydropyrrolo[1,2-]quinazolin-5(1)ones.

A highly regioselective synthesis of tetrahydropyrrolo1,2-]uinazolin-5(1)one derivatives was achieved by reacting cyclopropane aldehydes with '-aryl anthranil hydrazides in the presence of -toluene sulfonic acid (PTSA). The transformation involves domino imine formation and intramolecular cyclization to form 2-arylcyclopropyl-2,3-dihydroquinolin-4(1)-one, followed by nucleophilic ring opening of the cyclopropyl ring to form desired tetrahydropyrrolo[1,2-]quinazolin-5(1)one in good to excellent yield with complete regioselectivity. This protocol tolerates a great variety of functional groups and thus provides a simple and step-efficient method for pyrroloquinazolinone synthesis.