Palladium-Catalyzed Oxidative Coupling of Dibenzosiloles with α‑Diazo Esters: Formal Replacement of the Silyl Group with Carbenes

We report herein a Pd(II)-catalyzed oxidative coupling reaction of dibenzosiloles with aryl diazoacetates via a metal carbene migratory insertion process. In this reaction, carbenic carbon formally displaces silicon atoms through continuous cleavage of two C(sp2)–Si bonds and successive formation of two C(sp2)–C(sp3) bonds on a carbenic carbon. Density functional theory (DFT) studies reveal that the reaction proceeds through a Pd(II)/Pd(IV) catalytic cycle, in which the two C–Si bonds are cleaved by two successive oxidative addition/reductive elimination processes rather than traditional transmetalation steps. Additive o-chloranil was necessary for this reaction, which significantly facilitated the reaction by acting as both a ligand and an oxidant, and it played different roles in different reaction stages.