1 H NMR ( 400 MHz , DMSO - d 6 ) δ 10 . 70 ( s , 1 H ) , 8 . 62 ( s , 1 H ) , 7 . 68 ( d , J = 1 . 2 Hz , 1 H ) , 7 . 55 ( d , J = 8 . 4 Hz , 1 H ) , 7 . 34 ( dd , J = 1 . 6 , 8 . 4 Hz , 1 H ) , 7 . 02 ( dd , J = 8 . 4 , 8 . 4 Hz , 1 H ) , 6 . 93 ( s , 1 H ) , 6 . 77 - 6 . 78 ( m , 2 H ) , 6 . 46 - 6 . 48 ( m , 1 H ) , 4 . 53 ( s , 2 H ) , 3 . 34 ( s , 3 H ) .