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 CuCl2–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. It is demonstrated that a Pd(II)‐catalyzed oxidative cyclization of stilbenes bearing a pendent nucleophile operates through an uncommon Pd−C bond cleavage, 1,2‐aryl migration and CuCl2–assisted transient Pd oxidation, rather than generally preferred β–hydride elimination in alkylpalladium intermediates containing a syn β‐hydrogen atom.