1 H NMR ( 400 MHz , CDCl 3 , δ ) : 9 . 39 ( s , 1 H ) , 8 . 91 ( s , 2 H ) , 8 . 83 - 8 . 81 ( m , 1 H ) , 8 . 41 - 8 . 38 ( m , 2 H ) , 8 . 21 ( s , 1 H ) , 8 . 02 - 7 . 97 ( m , 3 H ) , 2 . 91 ( d , 9 H ) .