1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = 3 . 34 - 3 . 49 ( m , 2 H ) , 3 . 67 ( s , 3 H ) , 4 . 06 - 4 . 13 ( m , 1 H ) , 7 . 53 ( d , 2 H ) , 7 . 99 ( d , 2 H ) , 9 . 07 ( s , 1 H ) , 9 . 32 ( s , 1 H ) .