Aza‐Diels‐Alder Reaction of Danishefsky's Diene with Imine Catalyzed by N‐Heterocyclic Imidazole Halogen Bond Donors.

Recently, the halogen bonding catalysis in Aza‐Diels‐Alder reaction is increasing gloriously. In this work, the mechanism of the Aza‐Diels‐Alder reaction between imine and Danishefsky's diene catalyzed by N‐heterocyclic imidazole halogen bond donors has been explored with density functional theory. It is revealed that the reaction has two possible pathways: [4+2] cycloaddition pathway and Mannich pathway, in agreement with experimental predictions. Formation of halogen bond between the iodine atom of the catalysts and the N atom of the imine, results in lower energy barriers and more favorable of the reaction. The catalytic effect of the halogen bond can result in the electron rearrangement, which facilitates the formation of C−C bond. The stronger electron‐withdrawing ability of the group bonded to iodine atom of catalysts is, the better the catalytic activity is. These findings could be helpful to develop halogen bond donor catalysts in organic reactions. [ABSTRACT FROM AUTHOR]