Efficient Synthesis and Characterization of Novel Pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidines and Their Fused [1,2,4]triazole Derivatives

Both 3-aminothieno[2,3-b]pyridine-2-carboxamide derivative 4 and bis(3-aminothieno[2,3-b]pyridine-2-carboxamide) derivative 6 are prepared, starting with pyridine-2(1H)-thione derivative 1 incorporating 1,3-diarylpyrazole moiety, and were taken as starting materials for the present study. Two different synthetic routes are described for the synthesis of the target materials bis(pyridothieno[1,2,3]triazin-4-(3H)-one) derivative 7 and bis(pyridothienopyrimidin-4(3H)-one) derivatives 10 and 13. Pyridothienopyrimidin-4(3H)-one derivative 14 is used as a synthetic precursor for the preparation of 4-hydrazinylpyridothieno[3,2-d]pyrimidine derivative 18a. Compound 18a was reacted with acetylacetone to prepare the corresponding 4-(3,5-dimethyl-1H-pyrazol-1-yl)pyrimidine derivative 19. Compound 18a was reacted with several reagents such as carbon disulfide to synthesize the corresponding derivatives 24–27 incorporating fused [1,2,4]triazole ring. Moreover, 2,4-dihydrazinylpyridothieno[3,2-d]pyrimidine derivative 31 was prepared starting from 3-aminothieno[2,3-b]pyridine-2-carbonitrile derivative 28. Compound 31 was reacted with each of acetylacetone and formic acid to afford the corresponding 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyrimidine derivative 32 and bis([1,2,4]triazolo)[4,3-a:4′,3′-c]pyrimidine derivative 33, respectively. Elucidation of the structures of target molecules are achieved using elemental analyses and spectral data.