1H NMR (400 MHz, CDCl3) δ 8.23-8.14 (m, 2H), 8.11 (d, J = 8.1 Hz, 2H), 7.85-7.80 (m, 2H), 7.72 (t, J = 7.6 Hz, 1H), 7.51 (t, J = 7.5 Hz, 1H), 7.38 (d, J = 8.1 Hz, 2H), 2.54 (s, 3H). 13C NMR (100 MHz, CDCl3) δ 156.6, 148.2, 140.5, 136.9, 136.2, 129.8, 129.6, 127.9, 127.5, 127.2, 126.5, 126.2, 118.6, 15.6.