Mechanistic Insight into Diaurate-Catalyzed Synthesis of Benzofulvenes through C(sp3)–H Activation: A Computational Study

A wide range of gold-catalyzed reactions has continued to increase based on a dual activation mechanism. Herein, the diaurate-catalyzed synthesis mechanism of benzofulvenes through C(sp3)–H activation is thoroughly investigated by density functional theory (DFT). A few scenarios are highlighted, including the mode of catalyst transfer, the catalysis mechanism contrast between the Au center and two centers, and the manner of σ-gold coordinated diyne formation. Three mechanistic pathways were computed: (a) a dual-catalysis pathway of precatalyst (pathway a), (b) a single-catalysis pathway (pathway b), and (c) a dual-catalysis pathway including 9,8-H transfer (pathway c). As for the reasonable pathway a, NTf2– abstracts a proton from the π-gold complex, generating a σ-coordinated monogold complex. Subsequently, another catalyst coordinates, forming a σ,π-digold complex, which undergoes two consecutive cyclization steps to give non-gem-diaurated species. The reaction subsequently can proceed via three possible routes: (a1) undergo π-system slippage to yield gem-c, which then undergoes gold transfer and protonation with a substrate to afford benzofulvenes; (a2) intermolecular protodeauration to generate σ-monoaurated species, followed by protonation with HNTf2; and (a3) protonation by HNTf2 occurs to generate π-monoaurated species, which undergoes intermolecular protodeauration to form benzofulvenes.