1H NMR (400 MHz, CDCl3) δ 8.58 (s, 1H), 8.42 (d, J = 8.1 Hz, 1H), 8.10 (d, J = 7.6 Hz, 1H), 7.68 (t, J = 7.9 Hz, 1H), 6.03 (s, 1H), 5.70 (s, 1H), 3.55 (s, 2H), 2.16 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 194.5, 148.1, 143.4, 138.9, 134.9, 129.6, 126.9, 126.8, 124.3, 35.1, 15.6. HRMS (EI): calcd for C11H11NO3S: 237.0460; found: 237.0455.