Research On Transition-Metal-Catalyzed Aryl C-H Functionalization Reactions

Transition-metal-catalyzed C-H functionalization reactions have been regarded as the frontier of modern synthetic organic chemistry,and received widespread attention.Wherein the transition-metal-catalyzed aromatic C-H annulation reactions have became an efficient way to construct cyclic compounds with good selectivities.The development of transition-metal-catalyzed aryl C-H cyclization reactions has enabled chemists to build expected cyclic compounds from simple starting materials without any prefunctionalization when comparing with conventional condensation reactions and cross-coupling reactions.The topic of this dissertation is transition-metal-catalyzed functionalization reactions of aromatic C-H bonds,and the research work is focused on rhodium-catalyzed aryl C-H cyclization with unsaturated carbon-carbon double bonds.Moreover,the corresponding reaction mechanisms were investigated in depth.The main contents of this dissertation are as follows:1.Rh(III)-catalyzed controllable transformation of azobenzenes to indazoles and 2-acyl-NH-indoles is achieved via C-H functionalization.Experimental studies have shown that the reaction selectivity is controlled by the substrates.Rh(III)-catalyzed intermolecular cyclization of azobenzenes and acrylates provides a new method for the construction of indazole skeleton by oxidative Heck reaction with subsequent cyclization and aromatization,in which copper acetate is found to facilitate the oxidative olefination process.Furthermore,rhodium-catalyzed cyclization reaction of azobenzene with vinyl ketones or acrylamides represents a novel and efficient route for selective synthesis of 2-acyl-NH-indoles via olefin insertion/C-Rh bond nucleophilic addition towards N=N bond/aromatization tandem process,in which the coordination of copper acetate promote C-Rh bond nucleophilic addition towards N=N bond to deliver indole skeleton.2.Rh(III)-catalyzed cascade oxidative alkenylation/cyclization of picolinamides and alkenes to furnish pyrido pyrrolone derivatives is developed,in which three C-H bonds and one N-H bond broke,while one C-C bond and one C-N bond formed.The reaction proceeded with high yield and high regioselectivity and stereoselectivity.Moreover,copper acetate can also be used in catalytic amounts with O2 serving as the terminal oxidant.3.CuCl-catalyzed ortho C-H trifluoromethylation of arenes and heteroarenes has been realized,using the Togni reagent as the CF3 source.This reaction achieves the goal of regioselective trifluoromethylation of C-H bonds by regulating protecting group of anilines,changing reaction solvent,and optimizing reaction temperature.