1H NMR (400 MHz, CDCl3) δ 9.20 (s, 1H), 8.92 (s, 2H), 7.61 – 7.50 (m, 2H), 7.22 (t, J = 8.4 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ 163.40 (d, J = 249.7 Hz), 156.10 (d, J = 276.3 Hz), 133.46, 130.39, 128.78 (d, J = 8.3 Hz), 116.66, 116.44.