Metal-Catalyzed (4+3) Cyclization of Vinyl Aziridines with para-Quinone Methide Derivatives

The development of (4 + 3) cyclizations of vinyl aziridines, especially catalytic asymmetric versions, is needed in organic synthesis. This report describes an iridium-catalyzed (4 + 3) cyclization of vinyl aziridines with paraquinone methide (p-QM) derivatives, and this reaction constructs a seven-membered benzoxazepine scaffold in moderate to high yields (40% to 96%) and considerable diastereoselectivities (70:30 dr to >95:5 dr). Moreover, the catalytic asymmetric version of this (4 + 3) cyclization is accomplished in the presence of a palladium catalyst and a chiral ligand, and this modification provides chiral benzoxazepine derivatives in generally moderate diastereoselectivities (73:27 dr to 91:9 dr) and high enantioselectivities (92:8 to 96:4 er). This approach delivers a scarcely reported catalytic enantioselective (4 + 3) cyclization of vinyl aziridines and offers a metal-catalyzed (4 + 3) cyclization of p-QM derivatives.