Quinoxaline derivatives part II: Synthesis and antimicrobial testing of 1,2,4-triazolo[4,3-a]quinoxalines, 1,2,4-triazino[4,3-a]quinoxalines and 2-pyrazolylquinoxalines

Three main classes of quinoxaline derivatives have been synthesized. The fi rst class comprises the synthesis of three novel series of 1,2,4-triazolo[4 ,3-a]quinoxalines; namely 1-subsdtuted-1,2,4-triazolo[4,3-a]quinoxalines 3a -f, 1-substituted aminomethyl-1,2,4-triazolo[4,3-a]quinoxalines 14a-d and 1 -cyano or ethoxycarbonylmethyl-1,2,4-triazolo[4,3a]quinoxalines 6, 12. The second class involves the synthesis of 2-substituted-1H-1,2,4-triazinol[4,3 -a]quinoxalines 4a-d. The third class deals with the synthesis of a variety of 2-pyrazolylquinoxalines, namely 2-(5-amino-3-arylpyrazol-l-yl)-3-phenyl quinoxalines 5a-d, 2-[5-hydroxy-3-phenyl-4-(4-substituted sulfamoylphenyl)a zopyrazol-1-yl]-3-phenylquinoxalines 15a, b, and 2-(5-hydroxy-4-nitroso-3-p henylpyrazol-1-yl)-3-phenylquinoxaline (16). The prepared compounds were te sted in vitro for their antimicrobial activity. Compounds 13 and 14b exhibi ted promising antifungal activity against C. albicans (MIC 25, 50 mu/ml res pectively). Compound 13 was as active as the antibiotic nystatin.