The application of azoarenes in the synthesis of nitrogen-containing heterocycles

Azoarenes are efficient intermediates in synthetic organic chemistry. In this review, the application of azoarenes for the synthesis of nitrogen-containing heterocyles including pyrroles, benzotriazoles, triazolidines, indoles, indazoles, oxindoles, quinolines and its reduced derivatives, phenazines, hydropyridazinones, cinnolines, benzimidazoles and other useful N-containing heterocycles are reviewed and discussed. For this purpose, the reaction of azoarenes with various organic small molecules such as alkenes, alkynes, azides, NO₂ gas, nitroso, amino acids, azomethine ylides, canbonyl compounds, diazoesteres, sulfoxonium ylides, tosyl hydrazines, allyl halides, and many other reagents were investigated under metal/transition-metal catalysts, photocatalysts, or electrochemical conditions to afford the target heterocycles with at least one nitrogen atom. In this review, around 70 papers are summarized and discussed during the years 2000–2024.