The Dimroth rearrangement. Part XII. Transformation by alkali of 4-amino-3-benzyl-1,2,3-triazole and its 5-substituted derivatives into the corresponding 4-benzylamino isomers. Retrogression of this reaction in neutral solvents
Contrary to expectations, 4-amino-3-benzyl-1,2,3-triazole (Ic), and its 5-carbamoyl and 5-carboxy-derivatives, are partly isomerized in hot, basic solutions to equilibrium mixtures rich in 4-benzylamino-1,2,3-triazole (IIc) and its 5-carbamoyl and 5-carboxy-derivatives respectively. These secondary amines, all stable at 25° and hitherto unknown, retrogress in hot neutral solvents to equilibrium mixtures rich in the primary amine starting material. It is shown how these two equilibria can be manipulated for preparative use. New and improved preparations are described for (a) 4-amino-3-benzyl-1,2,3-triazole, by decarboxylation of the 5-carboxy-derivative; (b) this acid by alkaline hydrolysis of the corresponding amide; and (c) 4-amino-3-benzyl-5-cyano-1,2,3-triazole (Id), by the combined action of dimethylformamide and phosphoryl chloride on the related amide (the intermediate, 3-benzyl-5-cyano-4-dimethylaminomethyleneamino-1,2,3-triazole, was also isolated). The nitrile (Id) is dimerized by hot alkali to 6-amino-2-(4-amino-3-benzyl-1,2,3-triazol-5-yl)-9-benzyl-8-azapurine (IV). Physical constants are reported including u.v. spectra and ionization constants.