A novel synthesis of thieno[2,3-b]pyridine, pyridothienotriazine and pyridothienopyrimidine derivatives

Pyridinethiones 1a,b prepared according to literature procedures' were reac ted with chloroacetamide (2), p-chlorophenacylbromide (8), alpha-chloroacet ylacetone (11), ethylchloroacerate (15) to give 2-S-acetamidopyridines 3a,b , 2-S-aroylmethylpyridine 9[a](dagger), b, thieno[2,3-b]pyridines 14a,b and 2-S-ethoxycarbonylmethylpyridines 16a,b respectively. Cyclization reaction s on 3a,b, 9b, and 16a,b to synthesize 4a,b, 10a,b and 10a,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, a nd 2-hydrazonothieno[2,3-b]pyridines 25a-d through their reactions with ace tylacetone (20), formic acid and either aromatic aldehyde 23a,b or cinnamon itriles 24a,b respectively.