2-(2-Furfurylidene) acetylquinoxaline (Ia) and its 3-methyl analog (Ib) were cyclized to pyrrolo [1, 2-α] quinoxaline ring systems (IIa and IIb) by hydrochloric acid treatment. 2-(4-Methoxybenzylidene) acetylpyridine could be cyclized directly to the 2, 3-dihydroindolizine ring system (V) by treatment with perchloric acid. 2-Arylideneacetyl-3-methyl-quinoxalines (IX) also were cyclized to the corresponding pyrrolo [1, 2-α] quinoxaline systems by hydrochloric acid or perchloric acid. The cyclization of 2-(2-furfurylidene)-acetylquinoline (XI) was performed by using acetic anhydride in the presence of a catalytic amount of trifluoroacetic acid. 2-(2-Furfurylidene) acetylpyrazine (XIII) was cyclized easily by hydrochloric acid treatment. The structures of the adducts of these cyclic products with dimethyl acetylenedicarboxylate are discussed.
Quinocetone (3-methyl-2-quinoxalinbenzenevinylketo-1,4-dioxide; QCT) is a new promising antimicrobial growth promoter for quinoxalines. The identification of the major metabolites of QCT has resulted in a number of studies regarding its metabolic pathway. However, little is known about the systematic synthesis, characterization, and simultaneous determination of its metabolites. To obtain system data for the four main metabolites of QCT, a convenient synthesis of these compounds was performed. All synthesized compounds were characterized by infrared spectroscopy, nuclear magnetic resonance, and high-resolution mass spectroscopy. The theoretical N-O bond dissociation enthalpies (BDEs) and octanol-water partition coefficient (K-ow) were estimated. A cytotoxicity assay for these compounds in hepatocytes isolated from rats was proposed, and the cytotoxicity results were evaluated based on the calculated N-O BDEs. (C) 2012 Elsevier B.V. All rights reserved.
Improved synthesis of quinocetone and its two desoxymetabolites
Oxidation of o -nitroaniline with sodium hypochlorite afforded benzofurazanoxide in 96 % yield, and treatment of benzofurazanoxide with acetylacetone in the presence of triethylamine gave 2-acetyl-3-methyl-quinoxaline- -1,4-dioxide in 94 % yield. Finally, condensation of 2-acetyl-3-methyl-quinoxaline-1,4-dioxide with benzaldehyde using 4-(dimethylamino)pyridinium acetate as a catalyst led to