Mn(III)-Mediated Radical Cyclization of <i>o</i>‑Alkenyl Aromatic Isocyanides with Boronic Acids: Access to N‑Unprotected 2‑Aryl-3-cyanoindoles

The synthesis of N-unprotected 2-aryl-3-cyanoindoles was realized via the Mn­(III)-mediated radical cascade cyclization of o-alkenyl aromatic isocyanides with boronic acids. A possible mechanism involving a sequential intermolecular radical addition, intramolecular cyclization, and cleavage of the C–C bond under mild reaction conditions is proposed. Mechanism studies show that H2O or O2 might provide the oxygen source for the elimination of benzaldehyde.