Study On Photocatalytic Alkylation-Oxidation Tandem Reaction Of Alkenyl Borates

Alkenylboron compounds contain both alkene double bonds and boron functional groups,enabling a variety of transformations:1)Alkenylboron "ate" complexes can be obtained by lithiation of alkenylboron compounds,which undergoes 1,2-functional group migration to generate alkylboron compounds;2)Alkenylboron compounds can undergo radical addition reactions to synthesize alkylboron compounds via α-borylalkyl radicals intermediates;3)Alkenylboron compounds can undergo oxidation reaction,which can simply convert boron group into carbonyl group,thus effectively expanding its application range.However,in the literature reported so far,the introduction of new functional groups is rarely involved in the oxidation of alkenylboron compounds.This paper proposes an innovative photocatalytic alkylation-oxidation tandem strategy that combines alkyl radical addition and the oxidation of boron group to provide an efficient and simple method for the synthesis of α-alkyl-substituted carbonyl compounds.Chapter 1 systematically introduces the research progress of the transformation reactions of alkenylboron compounds.Based on the two key intermediates of alkenylboron "ate" complexes and α-borylalkyl radicals obtained from radical addition,the development of different types of inducing reagents in recent years are detailed,mainly including cationic,radical,and metal catalysts.In addition,this chapter also introduces various oxidative conversion reaction types of alkenylboron compounds,including alkaline hydrogen peroxide oxidation,sodium perborate oxidation,photocatalytic oxidation,heterogeneous catalysis and so on.Chapter 2 introduces the study on photocatalytic alkylation-oxidation tandem reaction.The effects of various parameters on reaction efficiency was systematically investigated.It was determined that under blue light irradiation,Ir(ppy)3 as photocatalyst,air as the green oxidant,α-alkyl-substituted carbonyl compounds can be obtained in moderate to good yields.Furthermore,the developed system has excellent functional group compatibility and a variety of radical precursors are compatible,such as α-halogenated carbonyl compounds,fluoroalkyl halides,and NHPI redox-active esters.In the mechanism exploration,a series of blank control experiments were designed to exclude potential stepwise reaction mechanisms,and a possible mechanism was proposed based on DFT theoretical calculations.Chapters 3 is the summary and prospect of the photocatalytic alkylation-oxidation tandem reaction.We summarized the challenges and limitations of this reaction,such as the extension of alkenyl boronic esters substrates and the replacement of metallic photocatalysts,etc.In the following study,relevant issues will be further explored in order to further optimize the reaction conditions.