1H NMR (400 MHz, CDCl3) δ 9.70 (s, 1H), 7.41 (d, J = 7.9 Hz, 2H), 7.21 (d, J = 7.8 Hz, 2H), 7.12 (d, J = 8.0 Hz, 2H), 7.05 (d, J = 7.5 Hz, 2H), 6.92 (t, J = 9.3 Hz, 4H), 2.31 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 193.04, 156.87, 140.58, 139.04, 137.77, 137.19, 136.11, 134.91, 132.82, 132.45, 132.33, 130.98, 129.09, 128.73, 128.32, 21.29.