Palladium-Catalyzed Formal (4+2) Cycloaddition between Alkyl Amides and Dienes Initiated by the Activation of C(sp3)−H Bonds

Abstract

We report a formal (4+2) cycloaddition between alkyl-nosylamides and dienes enabled by a palladium-catalyzed activation of C(sp3)–H bonds beta to the amide group. This atom economical reaction, which proceeds under operationally simple conditions, is compatible with a wide variety of dienes and provides a straightforward method to assemble different types of saturated lactams. The annulation is favored over alternative pathways in part because of the key role of the extra double bond of the diene partner. The use of suitable nitrogen-based additives as palladium ligands, which enable the C(sp3)–H activation without interfering in subsequent steps of the catalytic cycle, is also critical for the success of the reaction