Chemical Conversion Of Carbon Dioxide And Boron Compounds

In recent decades,carbon dioxide chemistry and boron chemistry have been the research hotspots.Carbon dioxide?CO₂?is a cheap,abundant,and renewable carbon resource.Its fixation and conversion play an important role in resource utilization and energy cycle.In addition,since the Suzuki-Miyaura coupling reaction was found to construct various carbon-carbon bonds,more and more researches were conducted on the borylation of other organic molecules with diboron compounds,especially Bis?pinacolato?diboron?B₂pin₂?.Based on this,we conducted research on the chemical conversion of CO₂ and the borylation participated by B₂pin_2.A new synthesis method,electrochemical synthesis was used,and some new reactions were found in our work.First of all,we used cuprous halide to catalyze the carboxylation of alkenyl boron compounds with CO₂,and various corresponding a,?-unsaturated carboxylic acids were obtained.There are three alkenyl boron compounds used,including alkenyl boronic acids,alkenyl boronic acid pinacol esters,and potassium?E?-trifluoro?styryl?borate.Compared with other transition-metal-catalyzed carboxylation of organoboron compounds with CO₂,our reaction advantages include milder reaction conditions,1 atm CO₂,simpler operation,cheaper cuprous halide catalyst,external ligand free,high yields and good functional group compatibility.For the mechanism,we believe that cuprous chloride?CuCl?first cooperates with the solvent N,N-Dimethylacetamide?DMA?to give the complex Cu?DMA?_nCl,which then participated in the catalytic cycle.Because of stability issue and the empty d orbital of copper,organocopper species has to be saturated by being coordinated with substrates,ligands or solvents.It is proved that DMA can be used as an acido ligand coordinating with copper.In addition,we realized the borylation of aryl iodides with B₂pin₂ via electrochemical method,obtaining the corresponding arylboronic esters.Compared with other borylation of aryl halides,our reaction advantages include transition-metal-free,short reaction time,and mild reaction conditions.Regarding to the reaction mechanism,Electron Paramagnetic Resonance?EPR?and Cyclic Voltammetry?CV?experiments proved that the formation of aryl radicals was driven by current;the"on/off experiment"proved that the continuous current played important role on the reaction.