Synthesis of Some 1,3-Thiazole, 1,3,4-Thiadiazole, Pyrazolo[5,l-c]-1,2,4-triazine, and l,2,4-Triazolo[5,l-c]-l,2,4-triazine Derivatives Based on the Thiazolo[3,2-a]benzimidazole Moiety

摘要

3-(3-Methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile was synthesized by refluxing ethyl 3-meth-ylthiazolo[3,2-a]benzimidazole-2-carboxylate, acetonitrile, and sodium hydride. Treatment of 3-(3-methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile with phenyl isothio-cyanate, in the presence of KOH, furnished the corresponding potassium salt which was converted into thioacetanilide derivative upon neutralization. The thioacetanilide derivative reacts with alpha-chloroacetylacetone and ethyl alpha-chloroaceto-acetate to give the 1,3-thiazole derivatives, while the reaction of the thioacetanilide derivative with hydrazonyl chlorides gave 1,3,4-thiadiazole derivatives. On the other hand, 3-(3-methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile reacted with the diazonium salt of both 3-phenyl-5-amino-(1H)-pyrazole and 5-arnino-l,2,4-(lH)-triazole to afford the corresponding hydrazones. The latter hydrazones underwent an intramolecular cyclization upon boiling in pyridine to give pyrazolo[5,l-c]-l,2,4-triazine and l,2,4-triazolo[5,l-c]-1,2,4-triazine derivatives. Moreover, the behavior of thiazolo[3,2-a]benzimidazol-3(2H)-one towards phenyl isothiocyanate followed by the reaction with alpha-chloroketones or hydrazonyl chlorides was investigated. Some of the latter compounds exhibited moderate effects against some bacterial and fungal species.