Transition metal-catalyzed C-H bond functionalization is widely developed due to its powerful and atom-economic advantage. To enable through-space interaction of a metal center with a neighboring C-H bond, metal migration strategy, including a C-H activation for forming a five membered palladacycle intermediate, has been frequently utilized. However, most reported 1,4-Pd migrations were limited to alkyl C(sp3)-Pd to aryl C(sp2)-Pd or aryl C(sp2)-Pd to aryl C(sp2)-Pd migrations. No research on alkyl C(sp3)-Pd to alkyl C(sp3)-Pd migration was reported.
During our recent study on regiodivergent cyclopropanation of σ-alkylPd(II)-intermediate A generated by Heck-type carbopalladation, unprecedented alkyl C(sp3)-Pd to alkyl C(sp3)-Pd migration was observed, from intermediate A to A', and it underwent β-hydride elimination to afford the quaternary vinylated oxindoles 2. To the best of our knowledge, this is the first example of an alkyl to alkyl 1,4-Pd migration.