Ligand Control The Selectivity Of Single And Double C(sp~2)-H Arylation

In recent decades,the C-H bond activation reaction has shown great advantages over traditional synthesis methods,and it is gradually becoming one of the main methods of synthesizing compounds.In particular,the transition-metal-catalyzed C-H arylation reaction can directly activate the inert C-H bond and avoid the pre-functionalization of the substrate to efficiently construct a series of aryl compounds.However,it is inevitable to encounter the problem of the selectivity of single and double arylation when there are two identical C-H bond activation sites in the aromatic ring.This paper introduces the development of transition-metal-catalyzed C-H arylation reaction and lists some representative research results.In the transition-metal-catalyzed C-H activation reaction,when there are two identical C-H activation sites,the selectivity of single and double arylation is always hard to control.In the C-H activation reaction,the traditional method usually adopts the method of controlling the iodobenzene equivalent or functional group occupation to solve the problem,but it can not fundamentally solve the problem of the selectivity of single and double arylation.In recent years,research results of C-H bond activation show that ligands play an important role in the transition-metal-catalyzed C-H arylation reaction.Ligands(pyridine-type ligands,amino acid-type ligands,and other types of ligands)can not only notably accelerate the C-H activation reaction,but also effectively control the site-selectivity and stereoselectivity of the C-H activation reaction.Therefore,the selectivity of single and double arylation of ortho-C(sp~2)-H bonds of phenylalanine derivetives was successfully controlled by adding pyridine ligands.This method features wide functional group tolerance.The research data showed that ligands are crucial for controlling the selectivity of single and double arylation.In the C-H activation reaction,the problem of controlling the selectivity of single and double arylation is essentially analyzed from the perspective of ligands.It has a great significance for further understanding the C-H activation reaction.