Dimroth Rearrangement of 5-Amino-1-phenyl-1H-1, 2, 3-triazole-4-carboxaldehyde and Related Compounds

Abstract

The 4-substituted 5-amino-1-phenyl-1H-1, 2, 3-triazoles, in which 4-substituent is formyl (1a), hydroxyiminomethyl (1b), and acetoxyiminomethyl groups (1c), were thermally isomerized to the corresponding 4-substituted 5-anilino-1H-1, 2, 3-triazoles (2a-c) by heating at 90°C in dimethyl sulfoxide. On the basis of the results obtained from the reaction in several kinds of solvents, it appears that this isomerization depends on the nature of the solvent used and the reaction temperature. In acetylation of 1a-c with acetic anhydride a similar isomerization proceeded concurrently, and the corresponding 4-substituted 1-acetyl-5-anilino-1H-1, 2, 3-triazoles (2d-f) were formed. The isomerization mechanism is discussed.