1H NMR (400 MHz, CDCl3) δ 8.70 (s, 1H), 7.58 (s, 1H), 7.45 (d, J = 2.6 Hz, 1H), 7.21 (d, J = 4.6 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 159.8 (s), 127.5 (s), 126.9 (s), 125.9 (s), 123.7 (s), 112.1 (s). HRMS (EI): calculated for C7H4N2O3S: 195.9943; found: 195.9942.