Cyclocondensation, antimicrobial activity and semi-empirical AM1-MO calculations of benzopyrone derivatives

Abstract

An efficient synthesis of 7-amino-9-hydroxy-6-oxo-6H-benzo[c]chromene-8-carbonitrile derivatives (2,6) and 4-methyl-2-oxo-2H-chromene-3-carbonitrile (5) via Claisen condensation of 2-hydroxyacetophenones (1,3) with ethyl cyanoacetate in the presence of sodium metal is reported. Reaction of 5 with thiosemicarbazide gave 1-(3-cyano-4-methyl-2-oxoquinolin-1(2H)-yl)thiourea (7). Treatment of 5 with 6,8-dichloro-4-oxo-4H-chromene-3-carboxaldehyde gave 4-(2-(6,8-dichloro-4-oxo-4H-chromen-3-yl)-2-hydroxyethyl)-2-oxo-2H-chromene-3-carbonitrile (9). Further treatment of 5 with ethyl acetate followed by condensation with 6,8-dichloro-3-formylchromone gave 7-((6,8-dichloro-4-oxo-4H-chromen-3-yl)methyleneamino)-9-hydroxy-6H-benzo[c]chromen-6-one (12). Structures of the products were established on the basis of elemental analysis, IR, ¹H and ¹³C NMR, mass spectra and semi-empirical AM1-MO calculations. The antimicrobial activities of the synthesized products were also studied.