Synthesis and Characterization of Some New 2-Iminochromene Derivatives

A series of new 2-iminochromene analogs was synthesized and structurally characterized by IR, NMR, and mass spectra. N-(4-Acetylphenyl)-6,8-dichloro-2-imino-2H-chromene-3-carboxamide, the intermediate for the target compounds, was prepared through the base-catalyzed condensation of 2-cyanoacetamide with 3,5-dichloro-2hydroxybenzaldehyde in piperidine. The hydrolysis of derivative 2-imino-2H-chromene-3-carboxamide with concentrated HCl formed N-(4-acetylphenyl)-6,8-dichloro-2-oxo-2H-chromene-3-carboxamide. 3-(4-Acetylphenyl)-2-amino-7,9dichloro-1-substituted-5-imino-3H-chromeno[3,4-c]pyridin-4(5H)-one and 1-acetyl-3-(4-acetylphenyl)-7,9-dichloro-5imino-2-methyl-3H-chromeno[3,4-c]pyridin-4(5H)-one were prepared through two methods by the treatment of 2-imino2H-chromene-3-carboxamide with acetonitrile derivatives, or acetylacetone in piperidine, and by Michael addition of the methylene group in acetonitrile derivatives or acetylacetone to the activated double bond in 2-imino-2H-chromene3-carboxamide. Further treatment of 2-imino-2H-chromene-3-carboxamide with the 3-(3,5-dimethyl-1H-pyrazol-1-yl)-3oxopropanenitrile gave the pyridine-1-carbonitrile. Finally, the cyclization condensation reaction of compound 2-imino2H-chromene-3-carboxamide with malononitrile dimer 2-aminoprop-1-ene-1,1,3-tricarbonitrilein DMF/TEA gave the 1,3-diamino-9,11-dichloro-5-aryl-7-imino-6-oxo-6,7-dihydro-5H-chromeno[3,4-c][1,8]naphthyridine-2-carbonitrile.