1H NMR (400 MHz, CDCl3) δ 9.27 (s, 1H), 8.98 (s, 2H), 7.79 (d, J = 7.7 Hz, 2H), 7.71 (d, J = 7.9 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ 158.20, 155.03, 137.85, 128.31, 127.43, 126.72, 126.43 (d, J = 3.7 Hz), 125.89.