1H NMR (400 MHz, CDCl3): δ 8.03-7.95 (m, 2H), 7.19-7.10 (m, 3H), 6.45 (d, J = 17.1 Hz, 1H), 5.94 (d, J = 10.6 Hz, 1H). 13C NMR (100 MHz, CDCl3): δ 189.4, 165.7(d, J = 255.0 Hz), 133.6 (d, J = 3.0 Hz), 132.0, 131.3 (d, J = 9.3 Hz), 130.4, 115.8 (d, J = 21.9 Hz).