Reaction of aromatic azides with strong acids: Formation of fused nitrogenheterocycles and arylamines

We describe in this paper the action of trifluoroacetic acid, trifluorometh anesulfonic acid and aluminum chloride upon ortho-substituted aryl azides t o form indoles, azepines and arylamines in good yields. The protonated azid es lose nitrogen to form arylnitrenium ion intermediates which undergo intr amolecular aromatic N-substitution. The acid decomposition of aryl azides i s compared with reported thermolyses.