1H NMR (400 MHz, CDCl3) δ 9.18 (s, 1H), 8.92 (s, 2H), 7.18 (s, 2H), 7.10 (s, 1H), 2.40 (s, 6H). 13C NMR (101 MHz, CDCl3) δ 157.26, 154.89, 139.12, 134.58, 134.18, 130.63, 124.83, 21.36.