Regioselective Brønsted Acid-Catalyzed Annulation of Cyclopropane Aldehydes with N′‑Aryl Anthranil Hydrazides: Domino Construction of Tetrahydropyrrolo[1,2‑a]quinazolin-5(1H)ones

A highly regioselective synthesis of tetra­hydro­pyrrolo[1,2-a]quinazolin-5­(1H)­one derivatives was achieved by reacting cyclopropane aldehydes with N′-aryl anthranil hydrazides in the presence of p-toluene sulfonic acid (PTSA). The transformation involves domino imine formation and intramolecular cyclization to form 2-arylcyclopropyl-2,3-dihydroquinolin-4­(1H)-one, followed by nucleophilic ring opening of the cyclopropyl ring to form desired tetrahydropyrrolo­[1,2-a]­quinazolin-5­(1H)­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.