Substituted ethyl 2-acyl-3-amino-6-methylthieno[2,3-b]pyridine-4-carboxylates as synthons for novel heterocycles

The triethylamine-catalyzed reaction of 4-substituted ethyl 2-acyl-3-amino-6-methylthieno [2,3-b]pyridine-4-carboxylates IIa-h with 2,2,6-trimethyl-4H-1,3-dioxin-4-one IV gave 4-dsubstituted ethyl 3-acetyl-2-hydroxy-7-methylthieno[2,3-b:4,5-b']dipyridine-9-carboxylates Va-h. Some of the thienodipyridines (V) reacted with excess IV to give 5-substituted ethyl 3-acetyl-4,8-dimethyl-2-oxo-2H-pyrano[2, pyrido[3',2':4,5]thieno[2,3-e]pyridine-10-carboxylates VI.