1 H NMR ( 400 MHz , DMSO - d 6 ) : δ 13 . 42 ( br s , 1 H ) , 10 . 24 ( s , 1 H ) , 8 . 25 ( d , J = 8 . 0 Hz , 1 H ) , 7 . 61 ( d , J = 8 . 0 Hz , 1 H ) , 7 . 44 ( m , 1 H ) , 7 . 36 ( m , 1 H ) ; mp 171 - 173 ℃