Direct aromatic amination by azides: reactions of hydrazoic acid and butyl azides with aromatic compounds in the presence of both trifluoromethanesulfonic acid and trifluoroacetic acid

Abstract

Reactions of hydrazoic acid with aromatic compounds in the presence of both trifluoromethanesulfonic acid (TFSA) and trifluoroacetic acid (TFA) efficiently gave primary arylamines without diamine contaminants. The reactions provide mainly the ortho- and para-monoamines even for readily oxidised aromatic compounds such as cumene, mesitylene, durene, isodurene and anisole. The mechanistic investigation demonstrates that the reactions proceed via a concerted process involving both arene attack on a conjugate acid of the azide and elimination of N₂ from the conjugate acid. The reaction of butyl azide with benzene and mesitylene in the presence of both TFSA and TFA produced N-butylarylamines in low yields together with high yields of butanal via a butylnitrenium ion intermediate; a similar reaction with tert-butyl azide gave no tert-butylarylamines.