Synthesis of some new azole, azepine, pyridine, and pyrimidine derivatives using 6-hydroxy-4H-4-oxo[1]-benzopyran-3-carboxaldehyde as a versatile starting material

Condensation of 3-formyl chromone 1 with hydroxylamine hydrochloride afforded the corresponding oxime 2 that was converted to nitrile 3. Refluxing of oxime 2 and/or nitrile 3 with aceturic or hippuric acid gave 16 and 17. Treatment of 1 with semicarbazide hydrochloride and thiosemicarbazide afforded the corresponding carbazones 5-6 that underwent cyclization with ethyl bromoacetate and/or chloroacetone yielding 7-8. Also 1 reacted with acyclic active methylene reagents, e.g. malononitrile, ethyl cyanoacetate, and ethyl acetoacetate to form compounds 11, 12, and 13. Reaction of 1 with bifunctional reagents, e.g. benzil, o-phenylenediamine, o-aminophenol, and o-aminothiophenol yielding the corresponding imidazolyl bezopyranone and azepine derivatives 14-20. Condensation of 1 with acyclic or heterocyclic compounds containing active methylene group, e.g. hippuric acid forming the condensed products 21-27.