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Abstract The current work illustrates the versatile role of 2-thioxobenzothiazinone moiety in the synthesis of different heterocyclic systems from simple readily obtainable materials. The work can be divided into four main parts:- i- Synthesis of 2-thioxobenzothiazinone and its reactions ii- Synthetic utility and chemical behaviour of 2-hydrazinylbenzothiazinone derivative iii- Synthetic utility and chemical behaviour of 2-(methylthio)-benzothiazinone iv- Study of biological activity of some synthesized compounds First part: Synthesis of 2-thioxobenzothiazinone and its reactions 2-Thioxo-1,2-dihydrobenzo[d][1,3]thiazin-4-one (1) and 1H-benzo[d][1,3]thiazine-2,4-dithione (2) have been synthesized via reaction of anthranilic acid and carbon disulfide (5 mL and / or 10 mL) in alcoholic potassium hydroxide heated to its refluxing temperature, respectively. The reactivity of benzothiazinone 1 towards some nucleophilic reagents namely, hydrazine hydrates and ammonium solution has been investigated and 2-hydrazinylbenzothiazinone derivative 3, and 2-aminoquinazolinone 4, have been obtained respectively. On the other hand the reactivity of benzothiazinone 1 towards some electrophilic reagents namely, methyl iodide in presence of potassium hydroxide and benzyl chloride in acetone containing anhydrous potassium carbonate has been investigated and S-methylated 5, and S-benzylated derivative 6 have been obtained respectively. Benzothiazinone derivative 7 have been formed via Mannich reaction of benzothiazinone 1 with p-anisidine and formaldehyde in presence of a catalytic amount of concentrated hydrochloric acid [cf. scheme I]. Scheme I Second part: Synthetic utility and chemical behaviour of 2-hydrazinylbenzothiazinone derivative 3 Heating 2-hydrazinylbenzothiazinone derivative 3 with fomamide, formic acid and/ or glacial acetic acid at refluxing temperature afforded benzotriazolothiazinone derivative 8, formyl derivative 9 and benzotriazolothiazinone derivative 10, respectively. Treatment of hydrazinylbenzothiazinone derivative 3 with acetylacetone in ethanol gave benzothiazinone derivative 11. Pyrazolone derivative 12 and pyrazolidindione derivative 13 have been formed via reaction of 2-hydrazinylbenzothiazinone derivative 3 with ethyl cyanoacetate in refluxing ethanol and diethylmalonate at 180 °C, respectively. Condensation of 2-hydrazinylbenzothiazinone derivative 3 with anhydrides namely, maleic and tetrachlorophthalic anhydrides in boiling dioxane yielded benzothiazinylpyridazine 14a and phthalazindione derivative 14b [cf. scheme II]. |