1 H NMR ( DMSO - d 6 , 400 MHz ) δ 8 . 51 ( d , J = 8 . 96 Hz , 1 H ) , 7 . 44 ( d , J = 7 . 3 Hz , 2 H ) , 7 . 34 ( t , J = 7 . 4 Hz , 2 H ) , 7 . 29 - 7 . 26 ( m , 1 H ) , 6 . 77 ( d , J = 8 . 96 Hz , 1 H ) , 4 . 52 ( s , 2 H ) , 4 . 01 ( s , 3 H ) ;