4-[4-(4-Fluorophenyl)-2-methyl-5-oxo-2,5-dihydroisoxazol-3-yl] -1-methylpyridinium iodide-4-[3-(4-fluorophenyl)-2-methyl-5-oxo-2,5- dihydroisoxazol-4-yl]-1-methylpyridinium iodide (0.6/0.4)

Abstract

The crystal structure of the title compound, C16H16FN2O2 +·I-, was determined as part of a study of the biological activity of isoxazolone derivatives as p38 mitogen-activated protein kinase (MAPK) inhibitors. The X-ray crystal structure of 4-[4-(4-fluoro-phenyl)- 2-methyl-5-oxo-2,5-dihydro-isoxazol-3-yl]-1-methyl-pyridinium iodide showed the presence of the regioisomer 4-[3-(4-fluoro-phenyl)-2-methyl-5-oxo-2,5-dihydro- isoxazol-4-yl]-1-methyl-pyridinium iodide. The synthesis of the former compound was achieved by reacting 4-(4-fluoro-phenyl)-3-(4-pyridyl)isoxazol-5(2H)-one after treatment with Et3N in dimethyl-formamide, with iodo-methane. The unexpected formation of the regioisomer could be explained by a rearrangement occurring via aziridine of the isoxazolone compound. The regioisomers have site occupancies of 0.632 (4)/0.368 (4). The two six members rings make a dihedral angle of 66.8 (2)°. © International Union of Crystallography 2008.