Rhodium(Ⅲ)-Catalyzed C-H Activation Based On Several Ditecting Groups

Rhodium-catalyzed directed C-H activation has become a new strategy of C-H bond functionalization for construction of C-X bond. In recent years, significant progress and extensive study has been made in this area. Rhodium-Catalyzed C-H functionalization directed by several groups is mainly studied in this thesis.The first chapter briefly introduces the related progress in Rh-Catalyzed directed C-H functionalization based on various directing groups. According to change on valency of Rh, the first chapter is divided into two broad categories:internal oxidation and external oxidation. Each category is divided into subclasses according to generic substructure of various directing groups.In second chapter, we report a study of rhodium(Ⅲ)-catalyzed internal oxidative olefination of arenes via C-H activation based on N-OH as directing group. The catalytic reaction, which unusually uses hydroxyl as both directing group and internal oxidant, has notable advantages such as mild conditions, high yields, broad substrate scope and atom economy. According to the mechanism experiments including KIE, H-D exchange, substrate competition and water capture, a possible catalytic cycle is proposed:Rh(Ⅲ)as the subject in catalytic cycle catalyzes reaction based on hydroxyl as directing group and the valency of Rh(Ⅲ) remains during the reaction process. Hydroxyl as internal oxidative group combines with proton to release water.The third chapter reports on a study of rhodium(Ⅲ)-catalyzed directed coupling of arenes with 2-vinyloxirane via C-H activation based on hydrazone and oxime as directing groups. This reaction proceeds efficiently under mild conditions with a low catalyst loading, especially the conditions with room temperature in the absence of additives for aromatic ketazines. A wide range of substituted substrates is supported. According to the experimental results of kinetic isotopic effect, reversibility studies and catalysis with rhodacycle intermediate c1, a possible mechanism is proposed:Rh(Ⅲ)-complex reacts with substrate to form five membered ring as stable intermediate which reacts with 2-Vinyloxirane to form product. An oxidation-reduction reaction takes place in two substrate molecules.The fourth chapter reports on a study of Rh(Ⅲ)-catalyzed directed coupling of arenes with disulfides via C-H activation based on hydrazone and oxime as directing groups. By construction of C-S bond under mild conditions, the reaction has increased C-X types. Likewise, on the basis of the mechanism experiments including KIE, H-D exchange, substrate competition and catalysis of Rh(Ⅲ)-complex intermediate, a reasonable catalytic cycle is proposed:symmetrical disulfide inserts into Rh(Ⅲ)-five-membered ring formed from Rh(Ⅲ)-catalyst and substrate. Then R-S+ and R-S- are delivered by cleavage of S-S bond. A fragment R-S+ combines with substrate to afford product and the other R-S- as ligand combines with Rh(Ⅲ)-complex to proceed with catalytic reaction.