1H NMR (400 MHz, CDCl3) δ 9.22 (s, 1H), 8.93 (s, 2H), 7.52 (d, J = 9.6 Hz, 4H). 13C NMR (101 MHz, CDCl3) δ 157.73, 154.75, 135.49, 132.72, 129.72, 128.80, 128.25.