Synthesis and reactivity of benzothiazol-2-ylcarbonylhydroximoyl chloride, a versatile synthon

The versatile, hitherto unreported benzothiazol-2-ylcarbonylhydroximoyl chloride (2) was prepared by treatment of the corresponding sulfonium bromide 1 with sodium nitrite and hydrochloric acid in dioxane. Compound 2 reacts with o-aminothiophenol and with o-phenylenediamine to afford the new ketones 3 and 4, respectively. Oxidation of the latter with lead tetraacetate gave the benzotriazine derivative 7. Reaction of 2 with heterocyclic amines furnished the novel fused heterocycles 8, 9, 12, 14 and 16. Compound 2 reacted also with 2-methylthiobenzimidazole and gave the new heterocyclic system 18. Treatment of 2 with acrylonitrile, acrylamide and alpha-(benzothiazol-2-yl)cinnamonitrile (25) in the presence of triethylamine afforded the isoxazole derivatives 21, 23 and 27, respectively. (C) 1997 Elsevier Science Ltd.