Efficient Synthesis and Characterization of Novel Pyrido[3′,2′:4,5]thieno[3,2‐<i>d</i>]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(1 H )‐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‐(3 H )‐one) derivative 7 and bis(pyridothienopyrimidin‐4(3 H )‐one) derivatives 10 and 13 . Pyridothienopyrimidin‐4(3 H )‐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‐1 H ‐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‐1 H ‐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.