Enaminones in heterocyclic synthesis: a new regioselective synthesis of 2,3,6-trisubstituted pyridines, 6-substituted-3-aroylpyridines and 1,3,5-triaroylbenzenes

1-Substituted-3-dimethylaminopropenones 1a-d reacted with acetylacetone and with ethyl acetoacetate to yield regioselectively 2,3,6-trisubstituted pyridines. Refluxing 1a-d in acetic acid/ammonium acetate resulted in the-formation of 6-substituted-3-aroylpyridines, whereas refluxing in acetic acid alone afforded 1,3,5-triaroylbenzene.