4,6-Diacetylresorcinol in Heterocyclic Synthesis, Part I: Synthesis and Biological Evaluation of Some New Linearly and Angularly Substituted Pyrano[3,2-g] Chromenes via Vilsmeier-Haack Formylation of 4,6-Diacetylresorcinol, Its Schiff Bases, and Hydrazones

Application of Vilsmeier-Haack reaction on 4,6-diacetylresorcinol (1) led 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 bases of 4,6-diacetylresorcinol (1) were subjected to Vilsmeier-Haack formylation reaction to afford 4,6-bis(alkyl/arylimino)-4H,6H-pyrano[3,2-g]chromene-3,7-dicarbaldehydes 10, 14, and 15. Also, treatment of some bis-hydrazones of 4,6-diacetylresorcinol 16-19 with Vilsmeier-Haack reagent afforded the corresponding 4,6-bis(4-formylpyrazol-3-yl)resorcinols 20 and 21, which underwent oxidation with iodine to yield the pyrano[3,2-g]chromeno[4,3-c:7,6-c]dipyrazole-4,8-diones 22 and 23, respectively. Most of the synthesized compounds revealed weak antimicrobial activities. It was noticed that the dicarboxaldehydes 2, 10, 14, and 15 exhibited moderate antibacterial activity against Gram-positive bacteria, yeast, and fungus. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications (R) for the following free supplemental resource(s): Full experimental and spectral details.]