1H NMR (400 MHz, CDCl3): δ 8.12 (d, J = 7.8 Hz, 1H), 7.48 (t, J = 7.4 Hz, 1H), 7.35 (t, J = 7.5 Hz, 1H), 7.25 (d, J = 7.1 Hz, 1H), 6.23 (s, 1H), 5.45 (s, 1H), 3.01 (t, J = 6.3 Hz, 2H), 2.87 (t, J = 6.2 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 187.6, 144.1, 143.3, 133.4, 133.1, 128.5, 128.2, 127.0, 121.7, 31.7, 29.7.