SYNTHESIS AND REACTIVITY OF 3-(BENZOTHIAZOL-2-YL)-3-OXOPROPANENITRILE

The versatile, hitherto unreported 3-(benzothiazol-2-yl)-3-oxopropanen itrile (3) was prepared by two convenient routes : either by the react ion of ethyl 2-benzothiazolecarboxylate (1) with acetonitrile in the p resence of sodium hydride or by treatment of 2-bromoacetylbenzothiazol e (2) with potassium cyanide. Reaction of 3 with heterocyclic diazoniu m salts furnished the corresponding hydrazones 6, 7 and 13, respective ly. The latter products underwent intramolecular cyclization into the corresponding pyrazolo[5,1-c]-1,2,4-triazine, 1,2,4-triazolo[5,1-c]-1, 2,4-triazine and 1,2,4-triazolo[4,3-a] benzimidazole derivatives 8, 9 and 14, respectively, upon boiling in pyridine. Compound 3 coupled als o with diazotized aromatic amines and gave the corresponding arylhydra zones 16a-c which undergo cyclocondensation with hydrazine and phenylh ydrazine to afford the pyrazole derivatives 17a-c and 18a-c, respectiv ely. Cyclocondensation of compound 3 with hydrazine derivatives afford ed the corresponding aminopyrazoles 19 and 20, respectively in good yi elds. Copyright (C) 1996 Elsevier Science Ltd