Palladium-catalyzed Ortho-C(sp~2)-H Activation Of Arylation

Compounds containing biphenyl structural fragments are relatively important,which can be widely used in medicine,natural products and materials.In the last few decades,the development of efficient,economical and environmentally friendly methods to build C-C bonds has been a hot spot in organic synthetic chemistry.Significant progress has been made in cross-coupling reactions catalyzed by transition metals.Though the cross-coupling reaction involving transition metal-catalyzed organometallic reagents has high yield and good selectivity,the substrates must be halogenated or metalized before the reaction,which makes the operation complicated and wastes a lot raw materials and time.In order to avoid these drawbacks,organic chemists have developed the method of C-H bond activation,which has become new wave of research.It is inevitable to involve the directing group in the study of C-H bond activation reaction.Due to the chelating coordination characteristic of the directing group,it can chelate with the transition metal to form a ring metal organic compound,which has been widely studied by organic chemists.In recent years,various directing groups have sprung up one after another.Scientists are committed to finding highly active directing groups that are easy to be introduced and removed.In this paper,the development of transition metals is briefly summarized,and the development and background of arylation are introduced.Some representative synthetic methods are listed.The development of build new C-C bonds from transition metals-catalyzed the cross-coupling reaction to the C-H activation reaction achieved a great leap in organic synthesis.C-H activation can directly,efficiently and selectively construct new chemical bonds.Also listed are some of the representative methods for C-H arylation,including the participation of different directing groups,and the participation of non-directing groups.In this paper,2-methoxyiminoacetyl(MIA)was used as a directing group to complete the direct arylation of the aryl ortho-C-H bond under Palladium catalysis,further enriching the synthesis method of methoxy oxime(MIA)-oriented arylation reaction.In this experiment,2-methoxyiminoacetyl(MIA)was used as the directing group,and the arylation reaction was carried out by utilizing the advantage of being able to form a bidentate ligand with palladium to realize the activation of the aryl ortho-C-H bond.The MIA directing group can be converted in situ after the reaction to maximize atomic utilization.By screening and optimizing the reaction conditions,the template reaction achieved a yield of 96%,and the universality of the substrate was also investigated.The results showed that the reaction had good universality to the substrate.In this paper,2-methoxyiminoacetyl(MIA)was used as the directing group to form C-C bond by C-H activation to achieve direct arylation of aryl ortho-C-H bond.2-methoxyiminoacetyl(MIA)directing group has unique structural characteristics,and the structure of dipeptide can be generated by hydrogenation after the reaction,which has broad application prospect in medicine molecules.The arylation compounds of arene play an important role in asymmetric catalysis,opening up new space for asymmetric catalytic ligand.