For the aromatic nucleophilic substitution step in this rearrangement reaction, when the substituent X is changed from CN to OMe, the classical stepwise mechanism to the borderline mechanism with dynamic intermediate can be clearly observed based on IRC. This phenomenon can be explained by Marcus theory 9 . When the substituent changes from electron withdrawing group to electron donating group, the stability of the Meisenheimer intermediate will gradually decrease, corresponding to the gradual increase of the relative energy of the intermediate. At this time, the potential energy curve of the intermediate will intersect with the potential energy curve of the product earlier, which leads to the emergence of dynamic intermediates. Moreover, as the ability of the substituents to give electrons increases, the lifetime of the dynamic intermediate will shortened to correspond to a narrower flat area in the IRC(Fig. ).