Transition metal mediated CÀH activation is a powerful synthetic tool for the total synthesis of complex natural products and biologically active molecules. The strategy involves mainly CÀH activation, nucleophilic addition and regeneration of the catalyst. It proceeds through a CÀH bond cleavage by ligand coordination to transition metal. Transition metals like Pd, Rh, Ru, Co, and Ir are the most often used catalysts, which form a complex with 2-aryl pyridine and facilitates the functionalization of various CÀH bonds to generate diverse CÀC and CÀX bonds under typically mild reaction conditions with low catalyst loading. In particular, the chelation-assisted cleavage of CÀH bonds at ortho-position of the pyridine directing group has been recognized as one of the most powerful strategies for the functionalization of unreactive CÀH bonds. Recently, transition metal catalyzed CÀH bond activation has received significant interest because it does not require the prefunctionalization of the substrate. Therefore, the metal-catalyzed CÀH activation and functionalization is currently considered as atom economy and simplified procedure in comparison with the traditional strategies.