1H NMR (400 MHz, CDCl3) δ 8.20-8.14 (m, 2H), 8.08 (d, J = 7.4 Hz, 2H), 7.83 (d, J = 8.6 Hz, 1H), 7.78 (d, J = 8.1 Hz, 1H), 7.70 (t, J = 7.7 Hz, 1H), 7.54 (d, J = 7.4 Hz, 2H), 7.49 (t, J = 7.5 Hz, 1H), 1.37 (s, 9H). 13C NMR (100 MHz, CDCl3) δ 157.4, 152.6, 148.3, 136.9, 136.7, 129.7, 129.6, 127.5, 127.4, 127.1, 126.1, 125.9, 119.0, 34.8, 31.3.