Ionic Liquid‐Catalyzed Annulation of 2‐Arylanilines and Diazo Compounds via Wolff Rearrangement

An acid‐functionalized ionic liquid‐catalyzed annulation of 2‐arylaniline and diazo compound was developed via cascade Wolff rearrangement, which is different from the precedent transformations mediated by metal or acid involving a NH bond insertion. A spectrum of diverse diazos were well compatible, in particular, the unsymmetrical diazos provided exclusive product through selective Wolff rearrangement. Mechanistic studies disclosed that the reaction proceeded through tandem Wolff rearrangement, nucleophilic addition, oxidation, and cyclization via the electrostatic interaction and hydrogen‐bonding effect of ionic liquid.