Oxidative Route to Indoles via Intramolecular Amino-Hydroxylation of o-Allenyl Anilines.

A new intramolecular oxidative amino-hydroxylation of o-allenyl anilines is reported. Treatment of carbamate-protected anilines with lead(IV) carboxylates in dichloromethane at room temperature results in facile tandem C-N (allene cyclization) and C-O bond formation (carboxylate trapping) to form indole products. Detailed reaction scope, mechanistic and kinetic studies suggest a reaction pathway involving an initial Wessely dearomatization step followed by cyclization and rearomatization.