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

Abstract

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.