A NOVEL SYNTHESIS OF THIENO[2,3-b]PYRIDINE, PYRIDOTHIENOTRIAZINE AND PYRIDOTHIENOPYRIMIDINE DERIVATIVES

Abstract Pyridinethiones 1a,b prepared according to literature procedures1 were reacted with chloroacetamide (2), p-chlorophenacylbromide (8), α-chloroacetylacetone (11), ethylchloroacetate (15) to give 2-S-acetamidopyridines 3a,b, 2-S-aroylmethylpyridine 9[a]†, b, thieno[2,3-b]pyridines 3a,b and 2-S-ethoxycarbonylmethylpyridines 16a,b respectively. Cyclization reactions on 3a,b, 9b, and 16a,b to synthesize 4a,b, 10a,b and 17a,b respectively. Nitrous acid, acetic anhydride and formic acid had been used to build a new additional ring in 5a,b, 6a,b and 7a,b through their reactions with 4a,b. Hydrazidic acid derivatives 18a,b used as a synthons for the preparation of 2-pyrazoloylthieno[2,3-b]pyridines 21a,b, pyridothienopyrimidines 22a,b, and 2-hydrazonothieno[2,3-b]pyridines 21a-b, through their reactions with acetylacetone (20), formic acid and either aromatic aldehyde 23a,b or cinnamonitriles 24a,b respectively.