Heterocycles [h]-Fused onto 4-Oxoquinoline-3-carboxylic Acid, V [1]. Synthesis and Antibacterial Activity of Some New 2,3-Disubstituted 7-Oxo-7,10-dihydropyrido[2,3-f]quinoxaline-8-carboxylic Acids and Esters

Abstract

Cyclocondensation reaction of ethyl 7,8-diamino-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate (2) or the -3-carboxylic acid 3 with sym-1,2-diketones produced the corresponding ethyl 2,3-disubstituted pyrido[2,3-f ]quinoxaline-8-carboxylates (4a -h) or the -8-carboxylic acids 5a -h, respectively. The structures for these new heterocycles are supported by analytical and spectral (IR, MS, NMR) data. Compounds 5a -c, g, h exhibit moderate activity against an assortment of bacterial species.

Fused-Ring Derivatives of Quinoxalines: Spectroscopic Characterization and Photoinduced Processes Investigated by EPR Spin Trapping Technique

“…The C=O stretching vibration of the ethyl carboxylate group for derivatives 2a – 2c differed in the 1726–1698 cm −1 region. The shift of this band towards lower wavenumbers can be explained by formation of intermolecular hydrogen bonds of pairwise grouped molecules around the inversion centers in the solid state via the carbonyl group of the ethyl ester and ethyl group at the 4-pyridone moiety as was observed for indolo[3,2- b ]- and [2,3- b ]pyrido[2,3- f ]quinoxaline-3-carboxylic esters [21,22]. The ring carbon-carbon and carbon-nitrogen stretching vibrations occur in the region 1630–1400 cm −1 , where several overlapping peaks were observed.…”

“…The large application potential of heterocyclic compounds containing the quinoxaline moiety motivated the preparation of new quinoxaline derivatives [8,21,22,23,24] and their further characterization. We focus attention on the photoinduced processes of 10-ethyl-7-oxo-7,10-dihydropyrido[2,3- f ]-quinoxalines (Figure 1) within the scope of their photoactivity, as the first step in the characterization and selection of the promising candidates for photobiological or luminescent applications.…”