Unusual 1,2‐Aryl Migration and Depalladation of Alkylpalladium Intermediates Containing a syn ‐β‐Hydrogen Atom

In general, alkylpalladium intermediates containing a syn β‐hydrogen atom are expected to undergo β–hydride elimination preferentially. However, this study unveils a new mechanistic mode in a Pd(II)‐catalyzed transformation, which leads to a series of both C−N/C−C bond forming and C−C bond forming/cleavage events. It has been demonstrated that a Pd(II)‐catalyzed oxidative cyclization of stilbenes bearing a pendent nucleophile such as 2‐alkenylanilines and 2‐alkenylphenyl 1,3‐diketones operates through an uncommon Pd−C bond cleavage assisted by a neighboring aryl group and CuCl 2 –assisted transient Pd oxidation, rather than generally preferred β–hydride elimination in alkylpalladium intermediates containing a syn β‐hydrogen atom. As a result, 1,2‐aryl migration occurs to lead to the unexpected formation of a variety of 3‐substituted indoles and 4‐aryl‐1‐naphthols. In addition, selective migration of an aryl group could be achieved from β,β‐disubstituted alkene substrates through alkylpalladium intermediates deprived of syn β‐hydrogen atom.