Synthesis of New 2‐[(Substituted‐pyrazolin‐1‐yl)carbonyl]‐thieno[2,3‐b]pyridine Derivatives

The reaction of 3‐amino‐4,6‐dimethyl‐2‐thieno[2,3‐b]pyridine carbohydrazide (1) with appropriate chalcones 2a‐2d in the presence of acid catalyst produced the corresponding 3‐amino‐2‐[(3,5‐disubstituted‐pyrazolin‐1‐yl)carbonyl]‐4,6‐dimethylthieno[2,3‐b]pyridines 3a‐3d. 3‐Amino‐2‐[(3‐substituted‐pyrazolin‐1‐yl)carbonyl]‐4,6‐dimethylthieno[2,3‐b]pyridines 7a, 7b were also obtained by the cyclization reaction of carbohydrazide 1 with Mannich base derivatives 6a, 6b under basic condition.