1 H NMR ( 300 MHz , CDCl 3 ) δ 3 . 44 - 3 . 52 ( 2 H , m ) , 4 . 62 - 4 . 70 ( 2 H , m ) , 6 . 75 ( 1 H , t , J = 6 . 8 Hz ) , 7 . 69 - 7 . 77 ( 3 H , m ) , 7 . 85 ( 1 H , dd , J = 6 . 8 , 1 . 5 Hz ) , 7 . 96 ( 2 H , d , J = 8 . 7 Hz ) .