| Olefins are one of the most important organic compounds,which can be engaged in various reactions,such as the electrophilic addition,hydrogenation,oxidation,and transition-metal-catalyzed cross-coupling.Recently,the radical addition to olefins has attracted considerable attention from synthetic chemists.However,due to the high reaction activity and weak stability of radical species,current studies have focused on the two-component reactions triggered by radical addition to olefins,and the three-component versions are still rare.Compared with two-component reactions,the three-component variants,utilizing simpler and more abundant starting materials,can assemble more carbon-carbon or carbon-heteroatom bonds in a single reaction,thus enabling a highly efficient and attractive method for organic synthesis.Therefore,the topic of this dissertation is the development of three-component reactions triggered by radical addition to alkenes,which consists of the following two chapters.First,a visible-light induced three-component reaction of alkenes,difluoroalkyl bromides,and alkynyl sulfones has been realized.It offers a rapid and general method for the construction of various β-difluoroalkylated alkynes under extremely mild reaction conditions.Various functional groups such as halides,alcohols,ethers,amides,silyl and boryl substituents are well tolerated.Preliminary mechanistic studies indicate that the reaction is initiated by the radical difluoroalkylation of alkenes,followed by addition to alkynes,and desulfonylation.This reaction constitutes the first intermolecular alkynyldifluoroalkylation of unactivated alkenes,which may be appealing for the rapid synthesis of difluoroalkylated compounds.Secondly,a novel nickel-catalyzed three-component reaction of alkenyl aldehydes,arylboronic acids,and tertiary a-carbonyl alkyl bromides has been developed.This reaction permits the simultaneous installation of both alkyl and aryl groups into alkenyl aldehdyes,thus delivering quaternary carbon center containing ketones in promising yields under mild reaction conditions.A wide range of functional groups,such as Br,Cl,F,CF3,CO2Me,CN,Ac,and OMe substituents,are compatible for the current process.Preliminary mechanistic studies indicate that the reaction is enabled by the combination of a rare l,n-HAT from alkyl radicals to aldehyde C-H bonds and nickel catalysis.It will be valuable for the realization of new remote C-H functionalization reactions by merging l,n-HAT with metal catalysis. |
