Borylation Reactions Based On Radical Cascade Reactions And Single Electron Transfer

Organoboron compounds have substantial applications in chemical synthesis,medicinal chemistry,and materials science.NHC-boryl radicals are a class of active species with special structures that can enable the construction of various chemical bonds.Although many borylation methods have been developed,there were few studies on the use of NHC-boryl radicals for the synthesis of organoboron molecules.Thus,it is highly desirable to explore their addition reactions with unsaturated compounds for the assembly of organoboron compounds.This thesis focuses on the development of new reaction pathways of NHC-boryl radicals to synthesize a variety of organoborons,including(1)NHC-boryl radical promoted promotes borylative cyclization reaction of 1,6-dienes to assemble boron-handled six-membered rings;(2)Photoredox catalysis enables new approaches for the generation and reactions of NHC-boryl radicals via single electron transfer.The first chapter summarized the application of Lewis base-boranes in organic synthesis with a focus on free radical reactions.In this chapter,the basic properties of Lewis base-boryl radicals and their applications were present,especially for the generation of NHC-boryl radicals and applications under photocatalytic conditions.The second chapter described the cascade reaction of NHC-boryl radicals with 1,6-dienes.The reaction selectively constructed boron-substituted six-membered cyclic,polycyclic even tricyclic with predictable regiocontrol and stereocontrol.In addition,the boron substituted derivatives of antidepressant paroxetine was achieved by this strategy and further transformations to other useful building blocks were demonstrated.The third chapter introduced a new strategy and a new pathway to generate NHC-boryl radicals by single-electron oxidation with photoredox catalysis.The generated boryl radicals could be used for defluoroborylation and arylboration of olefins.This new generation method of NHC-boryl radicals overcomes the traditional disadvantage of using free radical initiators and provides a new strategy for the synthesis of multifunctionalized substituted organoboron compounds.In this work,the author conducted detailed mechanistic studies and verified the oxidative generation of the NHC-boryl radical by cyclic voltammetry,fluorescence quenching experiments and radical clock experiments etc.