Synthesis of benzoheterocycles by palladium-catalyzed migratory cyclization through an unexpected reaction cascade.

Migratory functionalization of C-H bonds through metal migration from carbon to carbon under transition metal catalysis is a process of significant academic and industrial interest. Herein, a palladium-catalyzed migratory cyclization of α-bromoalkene derivatives ArXCBr=CH2, in which X denotes a phosphorus (P(O)R), silicon (SiR2), sulfur (SO2), carbon (C(O)), nitrogen (NTs), or oxygen-based moiety, affording various benzoheterocyclic compounds has been developed. Mechanistic investigations have demonstrated that the cyclization reaction proceeds through an unexpected cascade, with trans-1,2-palladium migration between sp2 carbons being a key step of catalytic cycle. To the best of our knowledge, this type of metal migration has not been reported previously.