Organocatalysis by Halogen, Chalcogen, and Pnictogen Bond Donors in Halide Abstraction Reactions: an Alternative to Hydrogen Bond Based Catalysis.

The application of sigma-hole interactions (halogen, chalcogen, and pnictogen bonds) in organocatalysis has attracted more and more interest in recent years. The catalysis mechanism of halogen, chalcogen, and pnictogen bonds in the chloride abstraction from Reissert-type substitution of isoquinoline has been investigated by the density functional theory. Compared with the reaction without catalysts, the reactions catalyzed by the sigma-hole interactions have lower energy barriers and are more favorable. The formation of the sigma-hole interaction between the Cl atom and halogen, chalcogen, and pnictogen bond donors facilitates the chloride abstraction reaction by weakening the strength of the C-Cl bond and decreasing the HOMO-LUMO gap of the reactants. The catalytic activity follows the sequence of pnictogen bonds > chalcogen bonds > halogen bonds, and shows an increase from period 3 to 5 in the same group, and pnictogen bond donors, especially tris (pentafluorophenyl) antimony show the best catalysis performance.