Electroreductive Hydroboration Of Olefins And Functionalization Of Unactivated Alkyl Halides

Organic synthesis is indispensable for human society as an important tool for the efficient construction of drug molecules as well as natural active molecules.With the continuous development of green organic chemistry,the field of electrochemical organic synthesis has gained more momentum in recent decades.Electrochemistry allows for the redox of substrates and the activation of organic media near the electrode by modulating the electrical potential,avoiding the use of highly polluting and toxic redox reagents in traditional chemistry,and gradually becoming an environmentally friendly nature of organic synthesis pathway.In this thesis,we reviewed the recent strategies of functionalization of olefins,hydroboration of olefins in conventional chemistry and electrochemical borylation from the perspective of electrochemical organic synthesis,small molecule activation and reductive coupling.The main research of this thesis is centered on cathodic reduction reactions,which generate alkyl radical intermediates by reduction to construct new C-X and C-C bonds.The details of the research are as follows.（1）Organoboron showed great potential in the synthesis of various high-value chemical compounds.Hydroboration of olefins has been proved to be the dominant method for the synthesis of organoboron compounds in conventional boron chemistry.Herein,an electroreductive anti-Markovnikov hydroboration approach of olefins with readily available B₂pin₂ to valuable organoboron compounds with high chemo-and regioselectivity under metal catalyst free conditions was reported.This protocol exhibited broad substrate scope and good functional-group tolerance on styrenes and heteroaromatic olefins,providing synthetically useful alkylborons with high efficiency,even various deuterium borylation products with good to excellent D-incorporation when CD₃CN was employed as the solvent.Furthermore,gram-scale reactions and extensive functional derivatization further highlighted the application potential of this method.（2）Alcohols are commonly used in the field of natural products and pharmaceutical sciences,Barbier reactions of unactivated alkyl halides under electrochemical conditions are developed by us,this strategy avoids the use of metal reagents in conventional Barbier reactions for the first time,overcomes the limitation of requiring activating substrates such as alkenyl,allyl or aryl halides,and achieves the reductive coupling reaction of unactivated alkyl halides with aldehyde substrates to prepare secondary alcohols without the involvement of metal catalysts.This protocol exhibits high functional group tolerance in good yields.（3）This thesis reports a strategy for reductive deuteration at the battery cathode using unactivated alkyl halides with cheap and readily available deuterium water as the deuterium source.This protocol achieves the deuteration of unactivated alkyl halides for the first time under electrochemical conditions without metal involvement,and avoids the use of activated halides and aryl halides commonly used in conventional halide deuteration strategies to obtain deuterated products with excellent D-incorporation（99%）and high yields.