1H NMR (400 MHz, CDCl3) δ 8.26-8.18 (m, 6H), 7.90 (d, J = 8.5 Hz, 1H), 7.84 (d, J = 8.1 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.56 (t, J = 7.5 Hz, 1H), 3.96 (s, 3H). 13C NMR (100 MHz, CDCl3) δ 166.9, 156.0, 148.2, 143.7, 137.1, 130.7, 130.1, 130.0, 129.8, 127.5, 127.4, 126.8, 119.8, 119.0, 52.2.