1H NMR (400 MHz, CDCl3): δ 8.21 (d, J = 8.2 Hz, 1H), 7.92 (d, J = 8.1 Hz, 1H), 7.82 (t, J = 7.5 Hz, 1H), 7.72 (dd, J = 21.5, 7.4 Hz, 3H), 7.59 (dd, J = 15.5, 7.6 Hz, 2H), 7.40 (s, 1H), 2.41 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 180.5, 151.2, 150.6, 148.1, 146.8, 134.2, 133.9, 132.7, 131.4, 131.2, 130.4, 129.2, 124.7, 124.4, 123.0, 121.6, 121.4, 17.9. HRMS (EI): calcd for C18H12N2O6S: 384.0416; found, 384.0420.