For the Pd(II)-catalysed C-H activation reactions, there are two main commonly accepted mechanisms: a) electrophilic aromatic substitution (SEAr) mechanism and b) proton-abstraction (PA) mechanism. The key step for the electrophilic aromatic substitution is an electrophilic attack by Pd(II) onto the aromatic substrate that also defines the regioselectivity of the overall process . The key feature of the proton abstraction (PA) mechanism is that the formation of the metal-carbon bond (M-C) occurs simultaneously with the cleavage of the carbon-hydrogen (C-H) bond, while the hydrogen is being transferred to a basic center, Scheme 1.