1H NMR (400 MHz, CDCl3) δ 9.21 (s, 1H), 8.74 (s, 1H), 7.40 – 7.28 (m, 1H), 7.21 (d, J = 7.1 Hz, 1H), 2.30 (s, 1H). 13C NMR (101 MHz, CDCl3) δ 157.19, 156.63, 135.69, 135.35, 134.25, 130.87, 129.84, 129.00, 126.46, 20.28.