The Activating Effect of Strong Acid for Pd-Catalyzed Directed C-H Activation by Concerted Metalation-Deprotonation Mechanism.

A computational study on the origin of the activating effect for Pd-catalyzed directed C-H activation by the concerted metalation-deprotonation (CMD) mechanism is conducted. DFT calculations indicate that strong acids can make Pd catalysts coordinate with directing groups (DGs) of the substrates more strongly and lower the C-H activation energy barrier. For the CMD mechanism, the electrophilicity of the Pd center and the basicity of the corresponding acid ligand for deprotonating the C-H bond are vital to the overall C-H activation energy barrier. Furthermore, this rule might disclose the role of some additives for C-H activation.