1H NMR (400 MHz, CDCl3) δ 9.22 (s, 1H), 8.92 (s, 2H), 7.65 (d, J = 7.8 Hz, 2H), 7.45 (d, J = 7.8 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ 157.77, 154.70, 133.35, 133.18, 132.68, 128.52, 123.65.