1H NMR (400 MHz, CDCl3): δ 7.79 (d, J = 8.4 Hz, 2H), 6.92 (d, J = 8.4 Hz, 2H), 5.80 (s, 1H), 5.53 (s, 1H), 3.86 (s, 3H), 2.06 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 197.2, 163.0, 143.9, 131.9, 130.0, 124.8, 113.4, 55.4, 19.1.