4,6-Diacetylresorcinol in Heterocyclic Synthesis Part II: Vilsmeier-Haack Reactions of 4,6-Diacetylresorcinol and Its Schiff Bases and Hydrazones to Construct of New Substituted Pyrano[3,2-g]chromenes

Application of Vilsmeier–Haack reaction on 4,6-diacetylresorcinol (1) leads to the formation of 4,6-dioxo-4H,6H-pyrano[3,2-g]chromene-3,7-dicarboxaldehyde (2) in good yield. The dicarboxaldehyde 2 was condensed with some carbon and nitrogen nucleophiles. Some aliphatic and aromatic Schiff basesof 4,6-diacetylresorcinol (1)were subjected toVilsmeier–Haack reagent to afford4,6-bis(alkyl/arylimino)-4H,6H-pyrano[3,2-g]chromene-3,7-dicarbaldehydes 10, 14 and 15. Wherever, treatment of some bis-hydrazones of 4,6-diacetylresorcinol 16-19 with Vilsmeier–Haack reagent afforded the corresponding 4,6-bis(pyrazole-3-yl-4-carboxaldehye)resorcinols 20 and 21 which underwent oxidation with iodine to yield fused polyheterocyclic systems 22 and 23, respectively.