1 H - NMR ( 500 MHz , CDCl 3 ) : 8 . 80 ( d , 1 H ) , 8 . 50 ( d , 1 H ) , 8 . 2 - 8 . 05 ( m , 2 H ) , 7 . 75 ( t , 1 H ) , 7 . 55 - 7 . 36 ( m , 3 H ) , 6 . 36 ( s , 1 H ) , 2 . 85 - 2 . 81 ( m , 4 H ) , 2 . 13 ( s , 6 H ) , 1 . 95 ( m , 2 H ) , 1 . 8 ( s , 6 H ) , 1 . 78 ( s , 3 H ) , 1 . 01 ( s , 6 H ) ppm