Gold-Catalyzed Skeletal Rearrangement of Alkenes: Regioselective Synthesis of Skeletally Diverse Tricyclic Heterocycles and Mechanistic Investigations

Transition metal-catalyzed skeletal rearrangement reactions have rapid advances in organic community. Their development benefits synthetic methodologies by providing versatile and flexible approaches toward special molecular scaffolds with high selectivity. Herein, a gold-catalyzed skeletal rearrangement of alkenes with alkynyl bromides is reported, enabling direct and regioselective generation of more than 50 examples of skeletally diverse tricyclic heterocycles, namely, syn-tetrahydrocyclopenta­[b]­indoles and benzofuro­[3,2-b]­pyridines, with generally good yields. This protocol could tolerate terminal unactivated and internal activated alkenes under air conditions, which is hitherto unreported in gold catalysis and scarcely realized by other metal-catalyzed reactions, thus opening avenues for the regioselective assembly of heterocyclic systems with high efficiency. Aside from examining the scope of this skeletal rearrangement, mechanistic investigations to explain the regioselectivity of forming syn-tetrahydrocyclopenta­[b]­indoles and benzofuro­[3,2-b]­pyridines were conducted by systematic theoretical calculations.