Regioselectivity C(sp~2)-C Bonds Formation Via Transition Metal Catalyst

The regioselective C-C bond formation has always been a research hotspot in the field of organicsynthesis chemistry.In recent years,with the vigorous development of C-H bond activation,it is the most direct,economical and efficient way to achieve C-C bond formation started from simple and basic C–H bonds.Due to the similitude of C-H bond on aromatics,it is difficult to reactivate a certain C-H bond with regioselectivity.As a result,a directing group strategy emerged.It perfectly solved the problem of regional selectivity,while other problems brought about by the introduction of the guiding group,such as how to install and remove it.In this thesis,the above-mentioned regioselective C-H functionalization reaction was explored,and functional groups were introduced selectively in ortho and meta positions.In addition,through the development of a novel catalytic system,the ortho C-H alkynylation and olefination of Cbz-amide-directed benzylamine compounds were successfully achieved.First,we have developed a ruthenium-catalyzed ligandenabled meta or ortho C-H selective benzylation via an oxidative C-H/C-H cross-coupling reaction of arenes with toluenes andcycloalkanes.The site selectivity from the ortho to the metaposition can be altered by modifying the ligand and rutheniumprecursor.Various arenes bearing pyridyl,pyridmidyl,andpyrazolyl directing groups can be selectively coupled withtoluenes at the meta positions in moderate to good yield,which highlights the important synthetic utility ofthis method in the construction of organic molecules.At the same time,we infer the possible structure of Ru(?)complex in catalysis by a large number of mechanism experiments.Second,benzyl chloroformate(Cbz-Cl)is frequently employed to protect the active amine groups during the construction of complex molecules in synthetic chemistry.Herein,a convenient and practical approach to synthesize ortho-alkynylated and olefinated arylalkylamines through ortho-selective C–H functionalization has been developed by using Cbz amide as the directing group and Ir(III)as the catalyst.Various substrates were well tolerated,affording the corresponding products in moderate to good yields.Moreover,preliminary mechanistic study revealed the role of the amide as the coordination center to cooperate with the Ir(III)complex during C–H activation.