Novel synthesis and ring closure reactions of 3-hydrazino-1,2,4-triazolo[3,4-<i style="">b</i>]benzothiazole

Abstract

625-6273-Hydrazino-1,2,4-triazolo[3,4-b]benzothiazole 2 is prepared by heating 3-chloro-1,2,4-triazino[3,4-b]benzothiazole-4(H)-one 1 with hydrazine hydrate. This transformation takes place with decarbonylation resulting in ring contraction and simultaneous replacement of chlorine by hydrazino group. Compound 2 on heating independently with urea and carbon disulphide in the presence of alkali gave 3'-hydroxy 3 and 3'-mercapto-1,2,4-triazolo[4',5':1,5]-1,2,4-triazolo[3,4-b] benzothiazole 4 respect­ively. Treatment of cold solution of 2 in phosphoric acid with sodium nitrite solution affords 1,2,3,4-tetra­zolo[1',5':1,5]-1,2, 4-triazolo[3,4-b]benzothiazole 5. 3'-Aryl-1, 2, 4-triazolo[4',5':1,5]-1, 2, 4-triazolo[3,4-b] benzothiazoles 7a-e have been also prepared by the reaction of 2 with aryl aldehydes in the presence of acetic acid