LAUSR

Abstract Starting from the ethyl 1-aminothieno(furo)[2,3-b]pyridine-2-carboxylates 1 by alkaline hydrolysis the corresponding potassium salts of thieno(furo)[2,3-b]pyridines 2 were obtained. Ongoing to the relevant acids (by treatment with hydrochloric acid), we have observed that while thieno[2,3-b]pyridines were converted into the 1-aminothieno[2,3-b]pyridine-2-carboxylic acids 3a–h in good yields (71−80%), in contrast, the derivatives of furo[2,3-b]pyridines gave the furo[2,3-b]pyridine-1-ones 5 (70−75%). Further, starting from the potassium salts or from amino acids of thieno(furo)[2,3-b]pyridines derivatives by refluxing in acetic anhydride a new heterocyclic system were obtained: 9(10)-methylpyrido[3',2':4,5]thieno(furo)[3,2-d][1,3]oxazin-7(8)-ones (65−89%). Finally the reaction of these latter compounds with benzyl amine or with hydrazine hydrate led to the formation of pyrimidine derivatives: 8(9)-benzyl-9(10)-methylpyrido[3',2':4,5]thieno(furo)[3,2-d]pyrimidin-7(8)-ones 7 (70−81%) and 8(9)-amino-9(10)-methylpyrido[3',2':4,5]thieno(furo)[3,2-d]pyrimidin-7(8)-ones 8 ones (72−81%). The structures of all synthesized compounds were confirmed by NMR, infrared, mass spectrometry data, and by elemental analysis. GRAPHICAL ABSTRACT The reactivity of some ethyl 1-aminothieno(furo)[2,3-b]pyridine-2-carboxylates 1 has been deeply investigated. By treatment with potassium hydroxide and then with hydrochloric acid they can give the relevant acids 3 or the 7,8-dihydro-2H-cyclopenta[d]furo(thieno)[2,3-b]pyridin-1(6H)-ones 5 (by decarboxylation and deamination). The acids 3 or their potassium salts react with acetic anhydride giving a new class of compounds (9(10)-methylpyrido[3',2':4,5]thieno(furo)[3,2-d][1,3]oxazin-7(8)-ones 6, which by reaction with benzylamine or hydrazine hydrate gave the new polyheterocyclic compounds: 8(9)-benzyl-9(10)-methylpyrido[3',2':4,5]thieno(furo)[3,2-d]pyrimidin-7(8)-ones 7 and 8(9)-amino-9(10)-methylpyrido[3',2':4,5]thieno[3,2-d]pyrimidin-7(8)-ones 8.