1,2,3-Triazoles. Part I. Some 4-aminotriazole-5-carbaldehydes

Abstract

4-Amino-1-(2- and 3-)methyl-1,2,3-triazole-5-carbaldehydes (1a–c) were made from the corresponding 5-carbonitriles by catalytic hydrogenation over palladium in hydrochloric acid of a critical strength. The 3-benzyl analogue was prepared by the same method. This and the 2-methyl analogue were also made by esterification of 4-amino-2-methyl-(or 3-benzyl-)1,2,3-triazole-5-carboxylic acid, followed by reduction of the product to give the 5-hydroxymethyl derivative [e.g.(3)] which was oxidized with manganese dioxide to the aldehyde. When 4-amino-2-methyl-1,2,3-triazole-5-carbonitrile was hydrogenated in the presence of phenylhydrazine, phenylsemicarbazide, or hydrazine hydrate, the phenylhydrazone, phenylsemicarbazone, or azine of the aldehyde were formed, but the free aldehyde could not be liberated from these derivatives. 4-Amino-1-methyl-1,2,3-triazole (5) was made by decarboxylating the 5-carboxylic acid. Dehydration of 4-amino-1,2,3-triazole-5-carboxamide with thionyl chloride in pyridine gave 4-amino-1-(2- or 3-)(4-pyridyl)-1,2,3-triazole-5-carbonitrile (6). The physical constants of these compounds are recorded and discussed. The protonation of 4-amino-2-methyl-1,2,3-triazoles is unusual, taking place on the primary amino-group.