Pericyclic or Pseudopericyclic? Deep Mechanism Insight into The Mi-gration Selectivity of Cb-Substituted-4aH-Carbazoles: Competition between Orbital Interaction and Electrostatic Interaction

The migration selectivity of Cb-substituted-4aH-carbazoles has been studied by DFT methods. For n-Bu and Ph substituted sub-strates, C4 migration and Ca-C1 migration are all pericyclic. C4 migration is favorable for more aromatic transition states. For halo-gen substituted substrates, C4 migration locates in the junction zone of pericyclic reactions and pseudopericyclic reactions while Ca-C1 migration is pseudopericyclic. Ca-C1 migration is favorable due to more positive NPA charges and LUMO distributions on Ca than C4. The acid catalysts with large steric hindrance can adjust the reaction selectivity through to some extent.