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.