Palladium-Catalyzed\nDearomative Heck/C(sp<sup>2</sup>)–H Activation/Decarboxylative\nCyclization of C2-Tethered\nIndoles

Until now, palladium-catalyzed dearomative Heck reactions\nof indoles\nwere largely limited to β-H elimination and nucleophilic capture\nof the transient alkyl-Pd(II) species. Herein, we disclose a novel\npalladium-catalyzed dearomative Heck/C(sp<sup>2</sup>)–H activation/decarboxylative\ncyclization of C2-tethered indoles. In this protocol, the alkyl-Pd(II)\nspecies formed by dearomatization of C2-tethered indoles is not terminated\nby common β-H elimination or nucleophilic capture, but rather\ngenerates <i>C</i>,<i>C</i>-palladacycle via C–H\nactivation. The latter is intercepted by α-bromoacrylic acids\nto produce pentacyclic and heptacyclic fused indolines.