Palladium-Catalyzed Intramolecular Hydroaminocarbonylation to Lactams: Additive-Free Protocol Initiated by Palladium Hydride

A palladium-catalyzed intramolecular hydroaminocarbonylation of 2-vinylbenzylamines in the absence of acidic or any other additives was realized via rational designing the catalytic system on the basis of mechanistic studies, which allows for the synthesis of a variety of six-membered lactams in good to excellent yields with high regioselectivity. The postulated palladium-hydride intermediate for initiating the hydroaminocarbonylation has been identified and directly used as a catalyst for the reaction. Further kinetic studies illustrated that the reaction rate is negative first-order-dependent on the substrate concentration with palladium hydride as a catalyst.