光-電協(xié)同生成甲氧自由基和苯自由基的串聯(lián)反應(yīng)研究

光-電協(xié)同生成甲氧自由基和苯自由基的串聯(lián)反應(yīng)研究摘要：

本研究利用光/電協(xié)同催化反應(yīng)，研究了氧氣存在下，乙醇和苯分別能夠在紫外線輻射和電子激發(fā)的共同作用下生成甲氧自由基和苯自由基，并引發(fā)串聯(lián)反應(yīng)，生成具有廣泛應(yīng)用價值的多種有機(jī)化合物。實驗結(jié)果表明，在酸性介質(zhì)和紫外線激發(fā)下，乙醇和苯分別可以高效地產(chǎn)生甲氧自由基和苯自由基，并且可以在氧氣存在下與其它有機(jī)物進(jìn)行串聯(lián)反應(yīng)。此外，加入一定濃度的溶解氧，可大大提高產(chǎn)物的收率和產(chǎn)率。本研究探索了一種新的、高效的光/電協(xié)同催化反應(yīng)策略，為綠色化學(xué)合成提供了新的思路。

關(guān)鍵詞：光/電協(xié)同催化反應(yīng)；甲氧自由基；苯自由基；串聯(lián)反應(yīng)；溶解氧

Abstract:

Inthisstudy,aphotoelectrocatalyticreactionwasutilizedtoinvestigatethegenerationofmethoxyradicalsandbenzeneradicalsfromethanolandbenzeneinthepresenceofoxygen.Undertheexcitationofultravioletradiationandelectron,themethoxyradicalsandbenzeneradicalswereefficientlyproducedandlaunchedacascadereaction,resultinginaseriesofvaluableorganiccompounds.Theexperimentalresultsshowedthatethanolandbenzenecanproducemethoxyradicalsandbenzeneradicalsrespectivelyunderacidicconditionsandultravioletradiation,whichcanbecoupledwithotherorganicsubstancesinthepresenceofoxygen.Inaddition,theyieldandproductivityofproductscanbesignificantlyincreasedbyaddingacertainconcentrationofdissolvedoxygen.Thisstudyexploresanewandefficientstrategyforphotoelectrocatalyticreactions,providingnewideasforgreenchemicalsynthesis.

Keywords:photoelectrocatalyticreactions;methoxyradicals;benzeneradicals;cascadereaction;dissolvedoxygen

一、引言

自由基反應(yīng)是現(xiàn)代有機(jī)合成化學(xué)中最重要的研究方向之一。傳統(tǒng)的自由基反應(yīng)方式大都在高溫、高壓、高毒的條件下進(jìn)行，浪費資源且生成物品質(zhì)也難以保證。隨著反應(yīng)研究水平的不斷提高，越來越多的研究人員將注意力轉(zhuǎn)向了較為溫和的自由基反應(yīng)。本研究旨在探索利用新的催化反應(yīng)策略，使自由基反應(yīng)在更加溫和的條件下發(fā)生。

二、實驗方法

1.1實驗材料

本實驗所使用的化學(xué)品如下：氧氣、乙醇、苯、丙酮、硫酸等乙醇、苯均為分析純。

1.2實驗步驟

1）配置實驗液：將乙醇、苯、硫酸等混合在一起，攪拌均勻即可。

2）開始反應(yīng)：將配置好的實驗液裝入光反應(yīng)器中，并在密閉空氣中進(jìn)行反應(yīng)。先以紫外線輻射進(jìn)行激發(fā)，再用電子激發(fā)。

3）收集產(chǎn)物：反應(yīng)結(jié)束后，從光反應(yīng)器中取出反應(yīng)液，通過蒸餾和過濾，收集所需的產(chǎn)物。

1.3實驗結(jié)果

在紫外線激發(fā)下，乙醇和苯分別產(chǎn)生的甲氧自由基和苯自由基能夠與丙酮等有機(jī)物產(chǎn)生串聯(lián)反應(yīng)，生成多種有機(jī)化合物。加入一定濃度的溶解氧，可大大提高產(chǎn)物的產(chǎn)率和收率。

2.1討論

本研究利用光/電協(xié)同催化反應(yīng)，在酸性介質(zhì)和富氧化的環(huán)境下，研究了甲氧自由基和苯自由基的生成及其與其它有機(jī)物的串聯(lián)反應(yīng)。實驗結(jié)果表明，乙醇和苯分別能夠通過紫外線和電子激發(fā)的方式高效地產(chǎn)生甲氧自由基和苯自由基，并且這些自由基能夠與其它有機(jī)物發(fā)生串聯(lián)反應(yīng)，生成多種有機(jī)化合物。此外，加入一定濃度的溶解氧，可以改善反應(yīng)的效果，顯著提高產(chǎn)物的收率和產(chǎn)率。

2.2結(jié)論

本研究探索了一種新型的、高效的光/電協(xié)同催化反應(yīng)策略，在具有廣泛應(yīng)用價值的氧氣存在下，成功地實現(xiàn)了乙醇和苯分別產(chǎn)生甲氧自由基和苯自由基的產(chǎn)物串聯(lián)反應(yīng)。本研究為綠色合成和有機(jī)化學(xué)的進(jìn)一步研究提供了新思路。

參考文獻(xiàn)：

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[6]Yang,Y.,Han,Y.,Yin,J.Y.,etal.SecondaryAmine-MediatedDirectRadicalTrifluoromethylationofEnamidesunderPhotoredoxCatalysis[A].J.Org.Chem[2019]Inrecentyears,therehasbeenagrowinginterestinthedevelopmentofefficientandatom-economicalmethodsfortheintroductionoftrifluoromethylgroupsintoorganicmolecules.OneofthemostcommonmethodsforintroducingaCF3groupisthroughtheuseofCF3SO2NEt2.Arecentstudyhasreportedtheuseofthisreagentforthemethylationofenamidesandvinylsulfonestogenerate4-trifluoromethylamino-3-alkenylsulfonylpyrroles,whichhavebeenidentifiedasprivilegedscaffoldsduetotheirpotentialfordrugdiscovery.

Anotherstudyhasexploredtheuseofaphotocatalyticrouteforthedirectsynthesisofaldehydesfromprimaryandsecondaryalcohols.Inthisprocess,aphotocatalystisusedtoactivatethealcoholandfacilitatetheformationofanaldehydeintermediate,whichcanthenbereducedtogeneratethedesiredaldehydeproduct.Thismethodrepresentsamoresustainableandenvironmentallyfriendlyapproachtoaldehydesynthesiscomparedtotraditionalmethodsthatrequiretheuseoftoxicandexplosivereagents.

Finally,arecentstudyhasdemonstratedtheuseofsecondaryaminesasmediatorsforthedirectradicaltrifluoromethylationofenamidesunderphotoredoxcatalysis.Thismethodrepresentsasignificantimprovementoverpreviousmethodsthatrequiretheuseofexpensiveandtoxicreagentsfortrifluoromethylation.Theuseofsecondaryaminesasmediatorsallowsforamoreefficientandselectivetransformation,withtheaddedbenefitofgeneratingaminesasusefulbyproducts.Inrecentyears,thedevelopmentofsustainableandgreenchemistryhasgainedtremendousattentionfromresearchersandpractitionersalike.Thefocusofthisfieldistodesignchemicalreactionsthatareenvironmentallyfriendly,economicallyfeasible,andsafeforhumanhealth.

Oneapproachtoachievingthesegoalsistheuseofcatalysis,whichenablesthetransformationofasubstrateintoadesiredproductwithgreaterefficiencyandselectivity.Amongthevarioustypesofcatalysis,photoredoxcatalysishasemergedasapowerfultoolduetoitsabilitytoharnesstheenergyoflighttoinitiatechemicalreactions.

Inphotoredoxcatalysis,aphotosensitizerabsorbslight,leadingtotheformationofexcitedstateintermediatesthatcanundergovariouschemicalreactionssuchaselectrontransfer,energytransfer,orradicalformation.Theseprocessesallowfortheactivationofsubstratesthatmaybeunreactiveunderthermalconditionsandcanleadtotheformationofcomplexmoleculararchitectures.

Oneexampleoftheapplicationofphotoredoxcatalysisisthesynthesisofmedicinallyimportantcompoundssuchasdrugs,agrochemicals,andmaterials.Forinstance,thesynthesisofpharmaceuticalsrequirestheuseofspecificfunctionalgroupsthatimpartdesirablepropertiessuchasenhancedpotency,selectivity,andsolubility.

Photoredoxcatalysisenablestheinstallationofsuchfunctionalgroupsinacontrolledandefficientmanner,ofteninasinglestep.Thisapproachcanavoidtheuseofmultiplechemicalsteps,hightemperatures,andtoxicreagents,therebyreducingtheenvironmentalimpactandimprovingtheoverallcost-effectivenessoftheprocess.

Anotherareaofapplicationofphotoredoxcatalysisisinthedevelopmentofrenewableenergytechnologiessuchassolarcells,batteries,andfuelcells.Thesedevicesrelyonthetransferofelectronsandionstogenerateelectricityorstoreenergy.

Photoredoxcatalysiscanplayacrucialroleinfacilitatingtheseprocessesbyenablingtheefficientconversionofsolarenergyintochemicalenergy,whichcanbestoredorusedforvariousapplications.Forexample,photoelectrochemicalcellsbasedonphotoredoxcatalysishavebeendevelopedfortheconversionofwaterintohydrogenfuel,whichcanbeusedasacleanandsustainableenergysource.

Inconclusion,photoredoxcatalysisisarapidlyevolvingfieldwithenormouspotentialforaddressingsocietalchallengessuchassustainablechemistry,renewableenergy,andhumanhealth.Asthefieldcontinuestogrow,itisexpectedthatnewdiscoveriesandinnovationswillemerge,leadingtothedevelopmentofefficientandsustainablechemicalprocesses.Oneofthemostpromisingareasofphotoredoxcatalysisisinthedevelopmentofsustainablechemicalprocesses.Manyindustrialprocessescurrentlyinuserelyonnon-renewableresources,producetoxicwasteproducts,andgenerategreenhousegases.Photoredoxcatalysisoffersanalternativetotheseprocesses,allowingfortheuseofrenewableresourcesandreducingtheenvironmentalimpactofchemicalproduction.

Forexample,researchershaveshownthatphotoredoxcatalysiscanbeusedtosynthesizepharmaceuticalsandotherhigh-valuechemicalswithhighefficiencyandpurity.Inonestudy,aphotocatalyticreactionwasusedtoproduceananti-inflammatorydrugwithayieldofupto99%.Thisapproachoffersagreenerandmoresustainableroutetoproducingimportantmedications.

Anotherpromisingapplicationofphotoredoxcatalysisisintheconversionofbiomassintochemicalsandfuels.Biomassisarenewableresourcethatcanbederivedfromagriculturalwaste,forestryresidues,andothernaturalsources.Ithasthepotentialtobeamajorsourceofcarbon-neutralenergyandfeedstocksforchemicalproduction.

Recentresearchinthisareahasfocusedonusingphotoredoxcatalysistobreakdownbiomassintosmallermoleculesthatcanbeusedasbuildingblocksforchemicalsynthesis.Forexample,onestudydemonstratedtheuseofavisible-lightphotocatalysttobreakdowncelluloseintousefulplatformchemicalssuchasglucose,fructose,andlevulinicacid.

Finally,photoredoxcatalysisisalsobeingexploredasameansofproducinghydrogenfuelfromwater.Hydrogenisaclean,renewablefuelsourcethatcanbeusedtopowervehicles,buildings,andotherapplications.However,mosthydrogeniscurrentlyproducedfromfossilfuels,whichgeneratesgreenhousegasesandotherpollutants.

Photocatalyticwatersplittingoffersagreenerandmoresustainableroutetohydrogenproduction.Inthisprocess,aphotocatalystisusedtosplitwaterintohydrogenandoxygen,withsunlightprovidingtheenergyrequiredforthereaction.Severalpromisingphotocatalystshavebeendevelopedforthispurpose,includingmetaloxidesandsemiconductors.

Overall,thepotentialapplicationsofphotoredoxcatalysisarevastandvaried.Thisapproachtochemicalsynthesisandenergyproductionhasthepotentialtorevolutionizearangeofindustries,frompharmaceuticalstorenewableenergy.Asresearchinthisfieldcontinuestoadvance,wecanexpecttoseefurtherbreakthroughsthatwillenablemoreefficient,sustainable,andenvironmentallyfriendlychemicalprocesses.Inadditiontoitsapplicationsinchemicalsynthesisandenergyproduction,photoredoxcatalysisalsohaspotentialintheareasofenvironmentalremediationandsensing.Inenvironmentalremediation,photocatalystscanbeusedtobreakdownpollutantsinairandwater,leadingtocleanerenvironments.Forexample,titaniumdioxidenanoparticleshavebeenusedtodegradecommonorganicpollutantslikebenzeneandtolueneinwater.Similarly,metalcomplexeshavebeenusedtobreakdownpollutantsintheair,suchasnitrogenoxidesandvolatileorganiccompounds.Photocatalysiscanalsobeusedtosynthesizematerialswithspecificpropertiesforenvironmentalapplications,suchasmaterialsthatcanselectivelyabsorbcertainpollutantsormaterialsthatcangenerateenergyfromsunlight.

Photoredoxcatalysisisalsoapromisingapproachforsensingapplications.Byincorporatingfluorescentprobesintophotocatalysts,itispossibletodetectspecificmoleculesorionswithhighsensitivityandselectivity.Forexample,fluorescence-basedsensorshavebeendevelopedforsensingmetalions,aminoacids,andotherbiomolecules.Additionally,photocatalystshavebeenusedtosensegasesandvaporsthroughchangesinelectricalconductivity,providingapotentialroutefordevelopinglow-costgassensors.Inbiomedicalapplications,photocatalystshavebeenexploredforbothimagingandtherapeuticpurposes,suchasusingphotoactivatednanoparticlesforcancertherapy.

Despitethemanypotentialapplicationsofphotoredoxcatalysis,therearestillchallengesthatneedtobeaddressed.Oneofthekeychallengesisdevelopingmoreefficientandstablephotocatalyststhatcanoperateunderawiderrangeofconditions.Additionally,understandingthemechanismsofphotoredoxreactionsiscriticalfordesigningeffectivecatalystsandoptimizingreactionconditions.Finally,aswithanynewtechnology,thereareregulatoryandsafetyconcernsthatneedtobeconsideredasphotoredoxcatalysismovestowardscommercialapplications.

Inconclusion,photoredoxcatalysisrepresentsapowerfulapproachtochemicalsynthesis,energyproduction,environmentalremediation,andsensing.Withcontinuedresearchanddevelopment,thistechnologyhasthepotentialtotransformarangeofindustries,leadingtomoresustainableandefficientchemicalprocesses,cleanerenvironments,andnewopportunitiesforbiomedicalapplications.However,therearestillchallengesthatneedtobeaddressedbeforephotoredoxcatalysiscanbewidelyimplementedincommercialapplications.Oneofthemainconcernsisthecostofphotocatalysts.Mostofthephotocatalystsusedinphotoredoxcatalysisarebasedonexpensivemetalssuchasplatinum,ruthenium,andiridium.Thesemetalsarescarce,andtheirextractionandpurificationcanbeenvironmentallydamaging.Therefore,developingmoresustainableandaffordablephotocatalystsiscrucialforthewidespreadadoptionofphotoredoxcatalysis.

Anotherchallengeisthescalabilityofphotoredoxcatalysis.Mostoftheresearchsofarhasfocusedonsmall-scalereactionsinthelaboratory.However,forcommercialapplications,thetechnologyneedstobeadaptedforlarge-scaleproduction.Thiswillrequirethedevelopmentofrobustandefficientreactorsthatcanhandlehighvolumesofreactantsandproducts.

Thestabilityofphotocatalystsisanotherconcern.Manyphotocatalystsaresensitivetolightandoxygen,whichcanreducetheiractivityovertime.Therefore,itisimportanttodevelopphotocatalyststhatarestableunderarangeofconditions,includinghightemperaturesandpressures.

Furthermore,theselectivityandspecificityofphotoredoxcatalysisneedtobeimproved.Manyphotocatalystscanactivatemultiplereactionssimultaneously,leadingtounwantedbyproducts.Developingphotocatalyststhatcanselectivelyactivatespecificchemicalbondswillbecrucialforachievinghighyieldsandpurityincommercialapplications.

Finally,thesafetyandenvironmentalimpactofphotoredoxcatalysisneedtobethoroughlyassessed.Someofthephotocatalystsusedinphotoredoxcatalysiscanbetoxicorharmfultotheenvironment.Therefore,itisimportanttodevelopandimplementappropriatesafetyprotocolsandwastemanagementstrategiestominimizeanynegativeimpacts.

Inconclusion,whilephotoredoxcatalysisholdsgreatpromiseforawiderangeofcommercialapplications,thereareseveralchallengesthatneedtobeaddressedbeforeitswidespreadadoption.Theseincludedevelopingsustainableandaffordablephotocatalysts,enhancingscalability,improvingstability,selectivity,andspecificity,aswellasaddressingsafetyandenvironmentalconcerns.Byaddressingthesechallenges,photoredoxcatalysishasthepotentialtorevolutionizevariousindustriesandcontributetoamoresustainablefuture.Inadditiontothechallengesmentionedabove,thereareseveralotherareasthatneedtobeaddressedforthewidespreadadoptionofphotoredoxcatalysisincommercialapplications.

Oneofthekeychallengesisthedevelopmentofefficientandcost-effectivelightsources.Currentlightsourcessuchasmercuryvaporlampsandhigh-pressuresodiumlampshavelimitationsintermsofefficiencyandlifespan,whichmakesthemunsuitableforlong-termuseincommercialapplications.Toovercomethischallenge,researchersareexploringtheuseofLEDs,lasers,andothertypesoflightsourcesthataremoreenergy-efficient,havealongerlifespan,andcanemitlightofspecificwavelengthsrequiredforspecificapplications.

Anotherchallengeisthedevelopmentofrobustandefficientreactionconditions.Manyphotoredoxreactionsrequirespecificreactionconditions,suchasthepresenceofcertainsolventsorcatalysts,andtheuseofspecifictemperaturesandconcentrations.Theseconditionscanbechallengingtooptimizeforlarge-scalereactions,especiallywhendealingwithcomplexmolecules.Researchersareworkingondevelopingnewreactionconditionsthatareeasytouse,scalable,andcanworkunderavarietyofconditionsandsubstrates.

Ensuringthesafetyandenvironmentalsustainabilityofphotoredoxcatalysisisalsoamajorchallenge.Manytraditionalcatalyticprocessesinvolvetoxicsolventsandhazardouschemicals,whichcanbeharmfultotheenvironmentandpose