Synthesis and anti-bacterial screening of ethyl 6-oxo-3-phenyl-1,6-dihydropyrano[3,2-e]indole-2-carboxylate and 7-phenyl-5H-pyrano [3?,2?:4,5]indolo[1,2-a]quinoxaline-6,10-dione

Ethyl 6-oxo-3-phenyl-1,6-dihydropyrano[3,2-e]indole-2-carboxylate 3a-c were synthesised from ethyl 2-[(2-oxo-2H-1-benzopyran-6-yl)-hydrazono]-3-phenylpropanoate 2a-c. Compounds 2a-c was in turn prepared by reacting diasotised solution of 6-aminocoumarin and ethyl-2-benzylacetoacetate. N-nitroarylation of ethyl 6-oxo-3-phenyl-1,6-dihydropyrano[3,2-e]indole-2-carboxylate 3a-c was carried out with 2-chloronitrobenzene to give ethyl 1-(2-nitrophenyl)-6-oxo-3-phenyl-1,6-dihydropyrano[3,2-e]indole-2-carboxylate 4a-c, which on catalytic reductive cyclisation with H2/Ni affords 7-phenyl-5H-pyrano[3?,2?:4,5]indolo[1,2-a]quinoxaline-6,10-dione 5a-c. The structures of all these compounds have been established on the basis of analytical and spectral data. All the compounds show significant antibacterial activity.