Theoretical Studies On The Mechanisms Of Rhodium-catalyzed C-H Activation Reactions Under Acidic Or Basic Additive Free Conditions

The Rhodium-catalyzed C-H functionalization reaction provides an effective way to convert the inert C-H bonds into C-X(X = C,N,O,S)bonds.In recent years the Rh-catalyzed C-H activation without acidic or basic additives has become one of the most focused topics.The mechanistic understanding of Rhodium-catalyzed C-H activation reactions under acidic or basic additive free conditions was carried out by Denisty Functional Theory(DFT)calculations.The detailed mechanism was uncovered for better understanding of the experiments.The following three aspects are included in this thesis:(1)The first chapter summarizes Rh-catalyzed C-H activation reactions under acidic or basic free conditions in the past few years,which were categorized by different directing group for a comprehensive demonstration of the developments and applications of this field.(2)The second chapter undertakes theoretical study on the pathways for C-H cleavage under Rh catalysis without any acidic or basic additive.The possible pathways for C-H cleavage in C-H functionalization of different substrates with cationic Cp*Rh(Ⅲ)were uncovered.The results have shown that the heteroatom-containing solvent,reactant,product,or even trace water could be possibly involved as a proton acceptor in different systems,assisting the C-H bond cleavage via an outer sphere CMD transition state.(3)The third chapter explores the origin of divergent chemoselectivity in Rh-catalyzed couplings of allyl acetates with benzamides and azobenzenes.Afther the formation of seven-membered rhodacycles,the reaction with an amide directing group undergoes favorable β-OAc elimination to produce olefination product.However,when the directing group is azobenzene,the β-H elimination occurs more easily due to more electron rich Rh center,leading to a different chemoselectivity and final formation of the alkylation product.