Skeletal Reconstruction of 3-Alkylidenepyrrolidines to Azepines Enabled by Pd-Catalyzed C–N Bond Cleavage

Herein we report a Pd-catalyzed C–N bond cleavage strategy for the cycloaddition of pyrrolidines with azlactones or butenolides to construct the azepines. Leverage of the readily accessible 3-alkylidenepyrrolidine can serve as an effective precursor for zwitterionic salts. The in situ formation of an allyl-palladium intermediate through the cleavage of inert, cyclic C–N bonds leads to a cascade [5 + 2] cycloaddition, which allows for the diverse synthesis of azepine scaffolds with good functional group tolerance and 100% atom economy.