Study Of Functionalization And Redox Deracemization Based On C(sp~3)-H Bond Activation

Direct transformation of C-H bonds to C-C bonds and C-X bonds has been regarded as an attractive research field in the organic chemistry.Compared with the traditional synthetic methods,this strategy can effectively shorten the reaction steps,improve the atom economy,and reduce the environmental contamination,which is in line with the concept of green chemistry.In Chapter I,a simple classification of the current researches on the direct functionalization of C-H bond together with a systematic summary of the progress on asymmetric functionalization of C(sp3)-H bond and functionalization of the distal inert C(sp3)-H bond initiated by free radical were summarized.In Chapter ?,an oxidative C(sp3)-H alkynylation of ?-substituted isochromans to provide ?,?-di-substituted isochromans was reported.The substrate was oxidized giving oxocarbenium intermediate by in the presence of DDQ and LiBF4,which was then captured by potassium alkyne trifluoroaborates providing the expected tertiary ether in high efficiency.This is mild and simple to operate and has good efficiency even when it is amplified to a gram-scale.This method established the first oxidative C-H functionalization of secondary ethers for tertiary ether preparation.In Chapter ?,a redox deracemization of 1,1-diaryl methanes was reported.In this study,manganese dioxide was used as an oxidant to oxidize the substrate in situ giving a relatively stable intermediate "para-quinone methide".Chiral phosphoric acid catalyzed asymmertric transfer hydrogen of the intermediate,complete the deracemization reaction.Two challenges have been solved in this method.First,the introduction of the 4-hydroxyl group on the benzene ring solved the problem of discrimination between two aromatic rings,and provided a driving force for oxidation to form a stable intermediate.Second,the low solubility of MnO2 in the reaction solution made it difficult to react quickly with the reductant in the reaction system,thus formally solving the problem of compatibility between the oxidant and reductant.The strategy provides a new idea for asymmetric synthesis of 1,1-diaryl methanesIn Chapter ?,a study on the functionalization of the distal inert methylene and methane C-H bonds was completed via 1,5-Hydrogen atom abstraction.The alkane compounds with hydrogen peroxide functional groups were used to generate alkoxy radicals catalyzed by Fe(?)species for subsequent fluorination and alkynylation.The substrates containing benzyl C-H bonds were also adopted as substrates for dual functionalzation of the 1,4-C-H bonds.