Palladium-Catalyzed\nCascade Distal C–H Methylation\nand Cyclization for the Construction of Spirooxindole Skeletons

Transition metal-catalyzed C–H methylation represents\na\nstraightforward approach for introducing methyl groups into organic\nmolecules. Herein, we report a palladium-catalyzed alkene-relayed\nremote C–H methylation reaction that utilizes dimethyl carbonate\nas the methylation reagent. The aryl groups distal to a bromo group\nwere dimethylated via C–H activation, leading to the formation\nof spirooxindoles as the final products through C(sp<sup>3</sup>)–H\nactivation and C(sp<sup>3</sup>)–C(sp<sup>3</sup>) coupling.\nThis cascade process involves the formation of four C–C bonds\nand the activation of three C–H bonds. The reaction not only\nprovides a new approach to C–H methylation but also offers\na novel method for constructing spirooxindole skeletons by merging\nskeleton construction and methylation into a single step.