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Abstract
Treatment of 2-methyl-pyrimido[4′,5′:4,5]thieno[2,3-b]-quinoxalin-4-one (2) with a mixture of phosphorous oxychloride phosphorous pentachloride affords 4-chloroderivatives (3). Treatment of 2 with phosphorous pentasulphide give the 4-thione derivative (4) which reacts with methyl iodide to yield the 4-methylthioderivative (6). Treatment of 3 with different nucleophiles, namely; hydrazinehydrate, aniline and dimethylamine, produce, 4-hydrazino-(5); 4-anilino-(7) and 4-dimethylamino-(8) derivatives, respectively. However, treatment of 3 with ethylglycinate gives 5-methyl imidazo[1″,2″: 1′,6′]pyrimido-[4′,5′:4,5]thieno[2,3-b]quinoxaline-3-one (9). 4-Hydrazino-2-methylpyrimido[4′,5′:4,5]thieno[2,3-b]quinoxaline (5) was condensed with p-substituted benzaldehydes to produce the corresponding hydrazones (10a–c). Treatment of 5 with acetic anhydride affords the hydrazinotriacetate compound (11), while with phthalic anhydride affords the corresponding 2-(pyrimido-thienoquinoxalin-4-yl)-dihydro-1,4-phthalazine dione (12). Treatment of 5 with acetylacetone produces 4-(3,5-dimethylpyrazol-1-yl)derivative (13). 4-Hydrazino compound 5 undergoes ring closure reactions with, formic acid, carbon disulfide, benzoyl chloride, ethylchloroformate or diethylmalonate to produce the s-triazolo ring system (17) and its derivatives; 3-thio-(14); 3-one-(18) and 3-methyl ethylcarboxylate-(19), respectively. Treatment of 5 with nitrous acid affords the tetrazolo compound (20).