Intermolecular α-Functionalization of Benzylamides with N-Nucleophiles via Oxidative Umpolung: Synthesis of Tetrasubstituted 3,3′-Oxindoles

A hypervalent iodine-mediated intermolecular alpha-umpolung reaction between alpha-aryl- or alkyl-substituted amides and benzotriazoles or purine derivatives as N-centered nucleophiles has been established. The reaction involves sequential intra/intermolecular oxidative C-N couplings in a controlled manner, affording tetrasubstituted 3,3 '-oxindoles in moderate to good yields. This approach efficiently addresses the challenges in constructing tetrasubstituted carbon centers via alpha-umpolung functionalizations of carbonyl compounds and serves as a new strategy for synthesizing biologically important 3,3 '-disubstituted oxindoles.