1 H - NMR ( 400 MHz , CDCl 3 ) δ : 8 . 23 ( 1 H , t , J = 6 . 4 Hz ) , 8 . 15 ( 2 H , d , J = 8 . 8 Hz ) , 7 . 73 - 7 . 70 ( 2 H , m ) , 7 . 52 ( 2 H , d , J = 8 . 8 Hz ) , 7 . 10 - 7 . 07 ( 2 H , m ) , 4 . 10 ( 2 H , d , J = 6 . 4 Hz ) , 3 . 82 ( 3 H , s ) .