Some reactions with quinoxaline-2,3-dicarboxylic acid anhydride: Novel synthesis of thieno[2,3-<i>d</i>]pyrimidines and pyrrolo [3,4-<i>b</i>]quinoxalines as antimicrobial agents

1486-1491The reactivity of quinoxaline-2,3-dicarboxylic anhydride 1 towards some heterocyclic amines as nitrogen nucleophiles has been investigated. Cyclic anhydride 1 on treatment with 2-aminobenzo[b]thiophenes 2a-c in refluxing ethanol, gives novel substituted quinoxalines 3a-c. On the other hand, fusion of compound 1 and 2b,c furnishes the corresponding quinoxalines 4a,b. Double cyclization occurs when compound 3b is refluxed with hydrazine hydrate to furnis polyheterocyclic system 6. Pyrroloquinoxalines 7a,b are obtained by refluxing compounds 3a,b in acetic anhydride. Dicarboxamides 8a-c are produced by fusion of 7b with aromatic amines. Thieno[2,3-d]pyrimidine 9 is obtained by refluxing the compound 4a or 4b with hydrazine hydrate. Condensation of compound 9 with aromatic aldehydes furnishes the corresponding Schiff bases 10a-c. Finally, refluxing of compound 9 with acetic anhydride yields the acetamido derivative 11