Catalytic access to carbocation intermediates via nitrenoid transfer leading to allylic lactams

Carbocation intermediacy is postulated in numerous organic transformations and provides the foundation for retrosynthetic logics in chemical synthesis. Although a number of catalytic approaches are designed to generate transient carbocations under mild conditions, there is room for improvement in the context of selectivity control and synthetic utility. Here we present an approach that enables catalytic access to carbocation intermediates via metal-nitrenoid transfer into alkenes, which subsequently allows a regiocontrolled elimination reaction. Customized catalysts are capable of bypassing competing pathways of the reactive intermediates to furnish valuable allylic lactams with excellent regioselectivity. Mechanistic investigations suggest that the ligand plays a critical role as an internal base in the selectivity-determining proton transfer process. This protocol is broadly applicable for preparing both five- and the more challenging four-membered allylamides. The virtue of this platform is further demonstrated by achieving the enantioselective construction of γ-lactams. The reactivity of transient carbocations provides interesting synthetic opportunities, but the selectivity control is challenging. Now, catalytic access to carbocation intermediates via metal-nitrenoid transfer into alkenes is reported and their regiocontrolled elimination is achieved, allowing the production of allylic lactams.