1H NMR (400 MHz, CDCl3) δ 9.17 (s, 1H), 8.93 (s, 2H), 7.47 (d, J = 7.7 Hz, 2H), 7.32 (d, J = 7.6 Hz, 2H), 2.42 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 157.20, 154.70, 139.13, 134.26, 131.32, 130.15, 126.80, 21.22.