Advances in Palladium-Catalyzed C-H Activation of Phenyl Substituted Heterocyclic Aromatics

The catalytic functionalization of carbon-hydrogen bond is the high efficient and atom economical strategy to construct carbon-carbon bond and carbon-heteroatom bond. It is also one of the hot topics in organic synthetic chemistry in recent years. Palladium catalysis in C-H bond activation has some advantages which include high catalytic activity, easily availability and high region-selectivity. In this paper, the latest advances in palladium catalyzed C-H activation of phenyl substituted heterocyclic aromatics in recent ten years are reviewed. The substrates involved phenyl substituted five- and six-membered heterocycle aromatics, which include phenylpyridines, phenylpyrimidines, phenylpyrazoles, phenyltriazoles, phenylthiazoles and phenyloxazoles. The different types of coupling reactions, such as arylation, acylation, cyanation and alkylation reactions are described in detail. The reaction mechanisms are also discussed on emphasis. The summary and prospects about the reaction are proposed.