[Synthesis]
The reaction was carried out with 4-chloro-7-nitrobenzo[c][1,2,5]oxadiazole (NBD-Cl) and 2-mercapto-pyridine-N-oxide, mixed in a 1:1 molar ratio, and stirred at room temperature for 10 min. Formation of precipitate was observed during the reaction. Subsequently, acetone (10 mL/0.1 g raw material) was added to the reaction mixture and stirring was continued. Upon completion of the reaction, the precipitate was collected by filtration through a G3 glass filter. The precipitate was further purified by preparative thin layer chromatography (TLC) using silica gel GF254 as stationary phase and a mixture of dichloromethane and methanol (10:0.2 v/v) as mobile phase, which was repeated three times. The final product was obtained as an orange-colored solid in 46% yield with a melting point of 198-199°C (literature value 201-202°C). Analysis by electrospray ionization mass spectrometry (ESI-MS) yielded the molecular ion peak [M+H]+ m/z 291, which is consistent with the calculated value of the molecular formula C11H6N4SO4 (M=290). The results of elemental analysis were as follows: calculated values C 45.52%, H 2.08%, N 19.3%, S 11.05%; measured values C 45.45%, H 2.03%, N 19.26%, S 11.01%. NMR hydrogen spectrum (1H-NMR, DMSO-d6, δ ppm, J Hz): 8.70 (d, 1H, H-6, J=7.4), 8.44 (bd, 1H, H-13, J=6.5), 8.05 (d, 1H, H-5, J=7.4), 7.39 (td, 1H, H-12, J=6.5, 3.1), 7.27- 7.22 (m, 2H, H-10, H-11). NMR carbon spectrum (13C-NMR, DMSO-d6, δ ppm): 150.73 (C-7), 146.07 (C-9), 143.47 (C-4), 136.98 (C-3), 128.52 (C-8), 138.61 (C-13), 136.63 (C-5), 131.88 (C-6), and 125.98 (C-10 or C-11), 125.84 (C-10 or C-11), 124.32 (C-12). Fourier transform infrared spectra (FT-IR, ATR, solid, ν cm-1): 3101w, 3076m, 3039w, 1518vs, 1469m, 1422s, 1363m, 1330s, 1275m, 1250s, 1227m, 1140m, 1044w, 958w, 890m, 843w, 808w. 758m, 733w, 704w. |