3-Amino-4,6-dimethylthieno[2,3-b]pyridine-2-carboxaldehyde was prepared and from it various functionalised
thieno[2,3-b; 4,5-b']dipyridines were synthesised, using the Friedländer and related reactions. Ethyl 2,7,9-
trimethylthieno[2,3-b; 4,5-b']dipyridine-3-carboxylate was transformed into a variety of thieno[2,3-b; 4,5-b']dipyridine
systems with heterocyclic rings attached at C-3 or fused at C2–C3.