1 H NMR ( 300 MHz , CDCl 3 ) : δ 7 . 59 ( d , J = 7 . 8 Hz , 2 H ) , 7 . 02 - 6 . 96 ( m , 2 H ) , 5 . 03 ( d , J = 9 . 9 Hz , 1 H ) , 3 . 78 - 3 . 66 ( m , 2 H ) , 2 . 85 - 2 . 67 ( m , 4 H ) , 2 . 04 ( s , 3 H ) , 1 . 38 ( s , 9 H ) .