The present invention relates to the compound of Formulas I, wherein n, R1, R2, R3a R4 and R5 are defined on summary of the invention of the invention It can inhibit the activity of MEK. The present invention also provides a kind of method for preparing catalyst, the compound of the present invention pharmaceutical preparation, the methods comprising this kind of compound, and are treating excessively proliferative disease such as cancer using these compounds and composition.
