1H NMR (400 MHz, CDCl3) δ 9.23 (s, 1H), 8.85 (s, 2H), 7.53 (d, J = 3.2 Hz, 1H), 7.39 (d, J = 3.2 Hz, 2H), 7.35 (s, 1H). 13C NMR (101 MHz, CDCl3) δ 157.64, 156.84, 133.42, 133.16, 132.81, 131.08, 130.40, 130.34, 127.49.