With ethyl β-aminocrotonate, the chromone 2A (X = H(A), Me(B), Cl(C)) gives a mixture of the dihydropyridine 4A and pyranopyridine 15A, 2B gives 4B, and 2C gives varying amounts of the substituted enamine 3C, pyridone 4C and benzophenone 8. 5-Hydroxy-5H-[1]benzopyrano-[4,3-b]pyridine 11 (< 3%) was obtained in each case. Palladised charcoal dehydrogenates dihydropyridines 4A and 4B to respectively 12A and 12B and ammonia converts 12A into the diazanaphthalene 13.
