Hydrogen auto-transfer under aerobic oxidative conditions: Efficient synthesis of saturated ketones by aerobic C–C cross-coupling of primary and secondary alcohols catalyzed by a Au6Pd/resin catalyst

Article abstract of DOI:10.1016/S1872-2067(16)62511-1

Au and Au-containing bimetallic nanoparticles are promising catalysts for the green synthesis of fine chemicals. Here, we used a Au₆Pd/resin catalyst for the aerobic C–C cross-coupling of primary and secondary alcohols to produce higher ketones under mild conditions. This is of importance to the construction of a C–C bond. Various substrates were used in the reaction system, and moderate to good yields were obtained. The catalysts can be reused at least five times without decrease of yield. The control experiment and XAFS characterization results showed that hydrogen auto-transfer occurred on metallic Pd sites even under oxidative conditions. On alloying with Au, the Pd sites became resistant to oxidation and readily abstracted the β-H of the alcohols and transferred the hydride to the C=C bond in the reaction intermediate to give the saturated product.

Full text of DOI:10.1016/S1872-2067(16)62511-1

ChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1764–1770
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
ꢀ
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
ꢀ
ꢀ
Article (Special Issue on Gold Catalysis)
Hydrogenꢀauto‐transferꢀunderꢀaerobicꢀoxidativeꢀconditions:ꢀ ꢀ
EfficientꢀsynthesisꢀofꢀsaturatedꢀketonesꢀbyꢀaerobicꢀC‒Cꢀ
cross‐couplingꢀofꢀprimaryꢀandꢀsecondaryꢀalcoholsꢀcatalyzedꢀbyꢀaꢀ
Au Pd/resinꢀcatalystꢀ
6
ꢀa,b,†
ꢀa,†
ꢀc
ꢀa
ꢀa
ꢀa,
MaoxiangꢀZhou ,ꢀLeileiꢀZhang ,ꢀJeffreyꢀT.ꢀMiller ,ꢀXiaofengꢀYang ,ꢀXiaoyanꢀLiu ,ꢀAiqinꢀWang *,ꢀ
ꢀa,#
TaoꢀZhang
ꢀ
aꢀStateꢀKeyꢀLaboratoryꢀofꢀCatalysis,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences,ꢀDalianꢀ116023,ꢀLiaoning,ꢀChinaꢀ
b
UniversityꢀofꢀChineseꢀAcademyꢀofꢀSciences,ꢀBeijingꢀ100049,ꢀChinaꢀ
cꢀCSE,ꢀArgonneꢀNationalꢀLaboratory,ꢀArgonne,ꢀILꢀ60439,ꢀUSAꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
AuꢀandꢀAu‐containingꢀbimetallicꢀnanoparticlesꢀareꢀpromisingꢀcatalystsꢀforꢀtheꢀgreenꢀsynthesisꢀofꢀ
Receivedꢀ15ꢀAprilꢀ2016ꢀ
Acceptedꢀ30ꢀJuneꢀ2016ꢀ
Publishedꢀ5ꢀOctoberꢀ2016ꢀ
fineꢀchemicals.ꢀHere,ꢀweꢀusedꢀaꢀAu Pd/resinꢀcatalystꢀforꢀtheꢀaerobicꢀC‒Cꢀcross‐couplingꢀofꢀprimaryꢀ
6
andꢀsecondaryꢀalcoholsꢀtoꢀproduceꢀhigherꢀketonesꢀunderꢀmildꢀconditions.ꢀThisꢀisꢀofꢀimportanceꢀtoꢀ
theꢀconstructionꢀofꢀaꢀC‒Cꢀbond.ꢀVariousꢀsubstratesꢀwereꢀusedꢀinꢀtheꢀreactionꢀsystem,ꢀandꢀmoderateꢀ
toꢀgoodꢀyieldsꢀwereꢀobtained.ꢀTheꢀcatalystsꢀcanꢀbeꢀreusedꢀatꢀleastꢀfiveꢀtimesꢀwithoutꢀdecreaseꢀofꢀ
yield.ꢀ Theꢀ controlꢀ experimentꢀ andꢀ XAFSꢀ characterizationꢀ resultsꢀ showedꢀ thatꢀ hydrogenꢀ au‐
to‐transferꢀoccurredꢀonꢀmetallicꢀPdꢀsitesꢀevenꢀunderꢀoxidativeꢀconditions.ꢀOnꢀalloyingꢀwithꢀAu,ꢀtheꢀ
Pdꢀsitesꢀbecameꢀresistantꢀtoꢀoxidationꢀandꢀreadilyꢀabstractedꢀtheꢀβ‐Hꢀofꢀtheꢀalcoholsꢀandꢀtransferredꢀ
theꢀhydrideꢀtoꢀtheꢀC=Cꢀbondꢀinꢀtheꢀreactionꢀintermediateꢀtoꢀgiveꢀtheꢀsaturatedꢀproduct.ꢀ
Keywords:ꢀ
Au‐Pdꢀalloysꢀ
C‒Cꢀcouplingꢀreactionꢀ
Oxidationꢀofꢀalcoholsꢀ
Hydrogenꢀauto‐transferꢀ
Oxidation‐resistant
©ꢀ2016,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1
.ꢀ ꢀ Introductionꢀ
C‒Cꢀ couplingꢀ reaction.ꢀ Amongꢀ these,ꢀ theꢀ hydrogenꢀ au‐
to‐transferꢀ strategy,ꢀ whichꢀ usesꢀ cheap,ꢀ stableꢀ andꢀ readilyꢀ
availableꢀ alcoholsꢀ asꢀ theꢀ alkylationꢀ regent,ꢀ hasꢀ attractedꢀ in‐
creasingꢀattentionꢀ(Schemeꢀ1(A))ꢀ[7].ꢀInꢀthisꢀprotocol,ꢀalcoholsꢀ
undergoꢀsequentialꢀdehydrogenationꢀorꢀaldolꢀcondensationꢀorꢀ
transferꢀ hydrogenationꢀ toꢀ affordꢀ higherꢀ alcoholsꢀ orꢀ ketonesꢀ
Theꢀ constructionꢀ ofꢀ complexꢀ andꢀ diverseꢀ moleculesꢀ fromꢀ
simpleꢀ substratesꢀ byꢀ C‒Cꢀ bondꢀ formingꢀ reactionsꢀ isꢀ aꢀ centralꢀ
themeꢀ inꢀ organicꢀ synthesisꢀ [1‒3].ꢀ Theꢀ traditionalꢀ synthesis,ꢀ
mainlyꢀ employingꢀ arylꢀ (alkyl)ꢀ halidesꢀ asꢀ theꢀ couplingꢀ regentꢀ
[
4‒6],ꢀsuffersꢀfromꢀlowꢀatomꢀefficiencyꢀdueꢀtoꢀtheꢀlargeꢀamountꢀ
withꢀH
ousꢀ catalystsꢀ [8,9]ꢀ andꢀ heterogeneousꢀ catalystsꢀ suchꢀ asꢀ Pd/Cꢀ
[10],ꢀAg/Al 3ꢀ[11]ꢀandꢀAu‐Pd/HTꢀ[12]ꢀhaveꢀbeenꢀusedꢀforꢀthisꢀ
reaction.ꢀ However,ꢀ severalꢀ drawbacksꢀ ofꢀ theseꢀ catalystsꢀ are:ꢀ
2
Oꢀand/orꢀH
2
ꢀasꢀtheꢀonlyꢀbyproduct.ꢀVariousꢀhomogene‐
ofꢀmassꢀlossꢀwithꢀtheꢀleavingꢀgroupꢀofꢀtheꢀalkylatingꢀagentꢀandꢀ
itꢀalsoꢀhasꢀtoxicꢀissues.ꢀEffortsꢀhaveꢀbeenꢀdevotedꢀtoꢀdevelopingꢀ
efficient,ꢀmild,ꢀandꢀstraightforwardꢀapproachesꢀtoꢀachieveꢀtheꢀ
2
O
*
ꢀ
†ꢀ
ꢀCorrespondingꢀauthor.ꢀTel:ꢀ+86‐411‐84379348;ꢀFax:ꢀ+86‐411‐84691570;ꢀE‐mail:ꢀaqwang@dicp.ac.cnꢀ ꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+86‐411‐84379015;ꢀFax:ꢀ+86‐411‐84691570;ꢀE‐mail:ꢀtaozhang@dicp.ac.cnꢀ ꢀ
Theseꢀauthorsꢀcontributedꢀequallyꢀtoꢀthisꢀwork.ꢀ
#
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀNationalꢀNaturalꢀScienceꢀFoundationꢀofꢀChinaꢀ(21373206,ꢀ21202163,ꢀ21303194,ꢀ21476227,ꢀ21503219).ꢀ
DOI:ꢀ10.1016/S1872‐2067(16)62511‐1ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ37,ꢀNo.ꢀ10,ꢀOctoberꢀ2016ꢀ ꢀ ꢀ

ꢀ
MaoxiangꢀZhouꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1764–1770ꢀ
1765ꢀ
1
.0ꢀgꢀofꢀPdCl ꢀinꢀ1.5ꢀmLꢀHClꢀ(12ꢀmol/L),ꢀandꢀthenꢀdilutedꢀtoꢀ50.0ꢀ
2
mLꢀ withꢀ milli‐Qꢀ water.ꢀ Theꢀ 717#ꢀ resinꢀ afterꢀ anionꢀ exchangeꢀ
wasꢀwashedꢀwithꢀwaterꢀseveralꢀtimesꢀuntilꢀtheꢀfiltrateꢀbecameꢀ
clean.ꢀAfterꢀdryingꢀatꢀ60ꢀ°C,ꢀtheꢀresinꢀwasꢀcrushedꢀwithꢀaꢀballꢀ
millꢀatꢀ250ꢀr/minꢀforꢀ1ꢀhꢀandꢀthenꢀsievedꢀtoꢀ100‒180ꢀmeshꢀforꢀ
useꢀasꢀtheꢀcatalystꢀsupport.ꢀTheꢀresinꢀsupportꢀwasꢀthenꢀsoakedꢀ
sequentiallyꢀinꢀNaOHꢀ(1.0ꢀmol/L),ꢀHNO3ꢀ(1.0ꢀmol/L),ꢀandꢀNaOHꢀ
(
1.0ꢀmol/L)ꢀforꢀ8ꢀh,ꢀandꢀfinallyꢀinꢀK
2
CO ꢀsolutionꢀ(2.0ꢀmol/L)ꢀforꢀ
3
24ꢀh.ꢀTheꢀresultantꢀionꢀexchangeꢀresinꢀwasꢀfilteredꢀandꢀwashedꢀ
withꢀ waterꢀ untilꢀ theꢀ filtrateꢀ becameꢀ neutralꢀ andꢀ thenꢀ driedꢀ
underꢀvacuumꢀatꢀ60ꢀ°Cꢀforꢀ12ꢀh.ꢀ
Schemeꢀ1.ꢀDifferentꢀprotocolsꢀofꢀC‒Cꢀcross‐couplingꢀreactionꢀofꢀprima‐
ryꢀandꢀsecondaryꢀalcohols.ꢀ
Monometallicꢀ Au/resin,ꢀ Pd/resinꢀ andꢀ bimetallicꢀ
Au‐Pd/resinꢀ withꢀ differentꢀ Au/Pdꢀ ratiosꢀ wereꢀ preparedꢀ withꢀ
theꢀ ionꢀ exchange‐NaBH
literatureꢀ[5].ꢀWithꢀAu Pd/resinꢀasꢀanꢀexample,ꢀ1.92ꢀmLꢀHAuCl
solutionꢀ (C(Au)ꢀ =ꢀ 9.56ꢀ mg/mL)ꢀ andꢀ 0.14ꢀ mLꢀ H PdCl
2.00ꢀmg/mL)ꢀwereꢀmixedꢀtogetherꢀinꢀ200ꢀmLꢀH O,ꢀfollowedꢀ
byꢀtheꢀadditionꢀofꢀ1.0ꢀgꢀ717#ꢀresinꢀandꢀstirringꢀforꢀ2ꢀhꢀinꢀdark.ꢀ
Theꢀ recoveredꢀ solidꢀ wasꢀ re‐dispersedꢀ inꢀ 30.0ꢀ mLꢀ water,ꢀ fol‐
4
ꢀ reductionꢀ methodꢀ reportedꢀ inꢀ theꢀ
first,ꢀtheꢀhomogeneousꢀmetalꢀcomplexꢀandꢀligandsꢀareꢀdifficultꢀ
toꢀrecycleꢀandꢀareꢀsensitiveꢀtoꢀmoistureꢀandꢀair;ꢀsecond,ꢀdueꢀtoꢀ
theꢀsluggishꢀdehydrogenationꢀofꢀalcohols,ꢀharshꢀreactionꢀcondi‐
tionsꢀareꢀemployedꢀ(temperatureꢀusuallyꢀaboveꢀ115ꢀ°Cꢀandꢀanꢀ
organicꢀsolventꢀisꢀused).ꢀForꢀthisꢀreason,ꢀitꢀisꢀhighlyꢀdesirableꢀtoꢀ
developꢀanꢀefficientꢀheterogeneousꢀcatalystꢀtoꢀaccomplishꢀtheꢀ
couplingꢀreactionsꢀofꢀalcoholsꢀunderꢀmildꢀreactionꢀconditions.ꢀ
Goldꢀandꢀgold‐containingꢀbimetallicꢀcatalystsꢀhaveꢀattractedꢀ
increasingꢀattentionꢀforꢀaꢀbroadꢀarrayꢀofꢀorganicꢀreactionsꢀbe‐
causeꢀofꢀtheirꢀuniqueꢀactivityꢀandꢀselectivity,ꢀasꢀwellꢀasꢀtheꢀmildꢀ
conditionsꢀ needed,ꢀ especiallyꢀ forꢀ aerobicꢀ oxidativeꢀ reactionsꢀ
6
4
ꢀ
2
4
ꢀ (C(Pd)ꢀ =ꢀ
1
2
lowedꢀbyꢀtheꢀadditionꢀofꢀ15.0ꢀmLꢀNaBH ꢀsolutionꢀ(10.0ꢀequiv.)ꢀ
4
andꢀstirredꢀforꢀ0.5ꢀhꢀinꢀdarkꢀtoꢀreduceꢀtheꢀmetalꢀprecursor.ꢀAf‐
terꢀfiltration,ꢀwashing,ꢀandꢀdryingꢀatꢀ60ꢀ°Cꢀforꢀ8ꢀhꢀunderꢀvacu‐
um,ꢀtheꢀcatalystꢀwasꢀobtainedꢀandꢀdenotedꢀasꢀAu Pd/resin.ꢀTheꢀ
6
otherꢀcatalystsꢀwereꢀpreparedꢀwithꢀtheꢀsameꢀmethodꢀexceptꢀforꢀ
aꢀ differentꢀ volumeꢀ ofꢀ theꢀ precursorꢀ solution.ꢀ Theꢀ totalꢀ metalꢀ
loadingꢀwasꢀcontrolledꢀatꢀ2.0ꢀwt%ꢀforꢀallꢀtheꢀcatalysts.ꢀAllꢀofꢀtheꢀ
catalystsꢀwereꢀstoredꢀinꢀairꢀbeforeꢀuse.ꢀ
[13‒16].ꢀ Recently,ꢀ ourꢀ groupꢀ developedꢀ aꢀ seriesꢀ ofꢀ Au‐basedꢀ
catalystsꢀforꢀtheꢀaerobicꢀoxidationꢀofꢀalcoholsꢀandꢀsilanes,ꢀandꢀ
theꢀaerobicꢀC‒Cꢀcross‐couplingꢀofꢀalcoholsꢀandꢀaminesꢀ[17‒19].ꢀ
Withꢀourꢀongoingꢀinterestꢀinꢀtheꢀaerobicꢀoxidativeꢀreaction,ꢀweꢀ
turnedꢀourꢀattentionꢀtoꢀanꢀalternativeꢀroute:ꢀanꢀaerobicꢀoxida‐
tiveꢀstrategyꢀtoꢀaccomplishꢀtheꢀdirectꢀcross‐couplingꢀreactionsꢀ
ofꢀsecondaryꢀandꢀprimaryꢀalcohols.ꢀToꢀourꢀdelight,ꢀbyꢀemploy‐
ingꢀanꢀionꢀexchangeꢀresinꢀsupportedꢀAu‐Pdꢀalloyꢀasꢀcatalyst,ꢀweꢀ
succeededꢀ inꢀ accomplishingꢀ theꢀ directꢀ cross‐couplingꢀ ofꢀ sec‐
ondaryꢀ andꢀ primaryꢀ alcoholsꢀ toꢀ produceꢀ higherꢀ ketonesꢀ
2.2.ꢀ ꢀ Catalystꢀcharacterizationsꢀ ꢀ
X‐rayꢀpowderꢀdiffractionꢀ(XRD)ꢀanalysisꢀwasꢀcarriedꢀoutꢀonꢀ
aꢀPANalyticalꢀX’pertꢀdiffractometerꢀusingꢀnickel‐filteredꢀCuꢀKαꢀ
radiationꢀwithꢀaꢀscanningꢀangleꢀ(2θ)ꢀofꢀ10°‒80°,ꢀoperatedꢀatꢀ40ꢀ
kVꢀ andꢀ 40ꢀ mA.ꢀ Highꢀ resolutionꢀ transmissionꢀ electronꢀ micro‐
scopeꢀ(HRTEM)ꢀcharacterizationꢀwasꢀcarriedꢀoutꢀwithꢀaꢀTecnaiꢀ
G2ꢀSpiritꢀ(FEI)ꢀmicroscopeꢀoperatingꢀatꢀ200ꢀkV.ꢀPriorꢀtoꢀobser‐
vation,ꢀaꢀpowderꢀsampleꢀofꢀtheꢀcatalystꢀwasꢀultrasonicallyꢀdis‐
persedꢀ inꢀ ethanolꢀ andꢀ aꢀ fewꢀ dropletsꢀ ofꢀ theꢀ suspensionꢀ wereꢀ
putꢀonꢀaꢀcopperꢀgridꢀcoveredꢀwithꢀaꢀholeyꢀcarbonꢀfilmꢀandꢀdriedꢀ
atꢀroomꢀtemperature.ꢀ
(Schemeꢀ 1(B))ꢀ underꢀ mildꢀ reactionꢀ conditionsꢀ underꢀ anꢀ O
2
ꢀ
balloonꢀatmosphere.ꢀAꢀwideꢀscopeꢀofꢀsubstratesꢀandꢀfunctionalꢀ
groupsꢀ canꢀ beꢀ usedꢀ inꢀ theꢀ reactionꢀ system,ꢀ andꢀ moderateꢀ toꢀ
goodꢀ yieldsꢀ ofꢀ theꢀ productsꢀ wereꢀ obtained.ꢀ Furthermore,ꢀ theꢀ
catalystꢀcanꢀbeꢀrecoveredꢀandꢀreusedꢀforꢀatꢀleastꢀ5ꢀtimesꢀwith‐
outꢀlossꢀofꢀactivity.ꢀ
X‐rayꢀ absorptionꢀ fineꢀ structureꢀ (XAFS)ꢀ spectraꢀ atꢀ theꢀ Auꢀ
L
III‐edgeꢀandꢀPdꢀK‐edgeꢀwereꢀmeasuredꢀatꢀtheꢀ14Wꢀbeamꢀlineꢀofꢀ
2
.ꢀ ꢀ Experimentalꢀ
.1.ꢀ ꢀ Catalystꢀpreparationꢀ
HAuCl ∙3H Oꢀ andꢀ PdCl ꢀ wereꢀ purchasedꢀ fromꢀ Shanghaiꢀ
ShanghaiꢀSynchrotronꢀRadiationꢀFacilityꢀ(SSRF)ꢀandꢀtheꢀinser‐
tion‐deviceꢀbeamlineꢀ10‐ID‐BꢀofꢀtheꢀMaterialsꢀResearchꢀCollab‐
orativeꢀAccessꢀTeamꢀ(MRCAT)ꢀatꢀtheꢀAdvancedꢀPhotonꢀSourceꢀ
atꢀArgonneꢀNationalꢀLaboratory.ꢀTheꢀX‐rayꢀabsorptionꢀspectraꢀ
wereꢀrecordedꢀatꢀroomꢀtemperatureꢀinꢀtheꢀtransmissionꢀmode.ꢀ
AuꢀfoilꢀandꢀPdꢀfoilꢀasꢀreferencesꢀwereꢀmeasuredꢀsimultaneouslyꢀ
usingꢀtheꢀthirdꢀionizationꢀchamberꢀsoꢀthatꢀtheꢀenergyꢀcalibra‐
tionꢀ couldꢀ beꢀ performedꢀ scan‐by‐scan.ꢀ Theꢀ X‐rayꢀ absorptionꢀ
dataꢀwereꢀprocessedꢀbyꢀtheꢀAthenaꢀsoftwareꢀpackage.ꢀ
2
4
2
2
ChemicalꢀReagentꢀCo.,ꢀLtd.,ꢀandꢀ717#ꢀionꢀexchangeꢀresinꢀ wasꢀ
providedꢀ byꢀ Sinopharmꢀ Chemicalꢀ Reagentꢀ Co.,ꢀ Ltd.ꢀ Otherꢀ
chemicalsꢀwereꢀpurchasedꢀfromꢀTianjinꢀKemiouꢀChemicalꢀRea‐
gentꢀCo.,ꢀLtd.ꢀAllꢀchemicalsꢀwereꢀanalyticalꢀgradeꢀandꢀusedꢀasꢀ
receivedꢀ withoutꢀ furtherꢀ purification.ꢀ Theꢀ waterꢀ usedꢀ inꢀ thisꢀ
studyꢀwasꢀdeionizedꢀbyꢀaꢀmilli‐QꢀPlusꢀsystem,ꢀhavingꢀ18.2ꢀMΩꢀ
electricalꢀresistivity.ꢀ ꢀ
2.3.ꢀ ꢀ Catalystꢀevaluationꢀ
Anꢀ aqueousꢀ solutionꢀ ofꢀ HAuCl
.56ꢀmg/mLꢀwasꢀpreparedꢀbyꢀdissolvingꢀ1.0ꢀgꢀofꢀHAuCl
inꢀ50.0ꢀmLꢀmilli‐Qꢀwater.ꢀAnꢀaqueousꢀsolutionꢀofꢀH PdCl
Pdꢀconcentrationꢀofꢀ12.00ꢀmg/mLꢀwasꢀpreparedꢀbyꢀdissolvingꢀ
4
ꢀ withꢀ Auꢀ concentrationꢀ ofꢀ
∙3H Oꢀ
ꢀwithꢀ
Unlessꢀotherwiseꢀnoted,ꢀtheꢀ reactionsꢀ wereꢀcarriedꢀoutꢀasꢀ
follows.ꢀ Aꢀ mixtureꢀ ofꢀ primaryꢀ alcoholꢀ (1.0ꢀ mmol),ꢀ secondaryꢀ
alcoholꢀ (0.5ꢀ mmol),ꢀ KOHꢀ (2.0ꢀ mmol)ꢀ andꢀ catalystꢀ (1.0‒3.0ꢀ
9
4
2
2
4

1766ꢀ
MaoxiangꢀZhouꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1764–1770ꢀ
2
mol%)ꢀ wasꢀ addedꢀ toꢀ 2ꢀ mLꢀ H Oꢀ inꢀ aꢀ testꢀ tube.ꢀ Theꢀ tubeꢀ wasꢀ
Tableꢀ1ꢀ
sealedꢀbeforeꢀevacuationꢀandꢀpurgingꢀwithꢀO
2
ꢀthreeꢀtimes.ꢀTheꢀ
CatalyticꢀperformanceꢀofꢀAu‐Pd/resinꢀforꢀC‒Cꢀcross‐couplingꢀreactionsꢀ
ofꢀalcohols.ꢀ
aꢀ
reactionꢀmixtureꢀwasꢀvigorouslyꢀstirredꢀatꢀ60ꢀ°Cꢀforꢀ6ꢀhꢀunderꢀ
anꢀ oxygenꢀ balloon.ꢀ Afterꢀ coolingꢀ downꢀ toꢀ roomꢀ temperature,ꢀ
theꢀ catalystꢀ wasꢀ separatedꢀ byꢀ filtrationꢀ andꢀ theꢀ filtrateꢀ wasꢀ
extractedꢀwithꢀethylꢀacetateꢀ(2ꢀ×ꢀ20.0ꢀmL).ꢀTheꢀorganicꢀlayerꢀ
wasꢀdriedꢀoverꢀanhydrousꢀmagnesiumꢀsulfate.ꢀAfterꢀaddingꢀ100ꢀ
μLꢀ n‐dodecaneꢀ asꢀ theꢀ internalꢀ standard,ꢀ theꢀ organicꢀ mixtureꢀ
wasꢀ submittedꢀ toꢀGCꢀ analysisꢀ forꢀconversionꢀandꢀyieldꢀ deter‐
mination.ꢀTheꢀcrudeꢀproductꢀwasꢀpurifiedꢀbyꢀflashꢀchromatog‐
raphyꢀonꢀaꢀshortꢀsilicaꢀgelꢀ(eluent:ꢀpetroleumꢀether/ethylꢀace‐
tateꢀ=ꢀ10/1,ꢀ2/1).ꢀ
Yieldꢀ(%)ꢀbꢀ
Conversion
ofꢀ1bꢀ(%)
Entryꢀ
Catalystꢀ
1cꢀ
18ꢀ
11ꢀ
26ꢀ
28ꢀ
ꢀ 5ꢀ
ꢀ 3ꢀ
1dꢀ
ꢀ 0ꢀ
ꢀ 0ꢀ
13ꢀ
16ꢀ
45ꢀ
70ꢀ
1eꢀ
16ꢀ
37ꢀ
29ꢀ
18ꢀ
30ꢀ
25ꢀ
1
2
3
ꢀ
ꢀ
ꢀ
34ꢀ
48ꢀ
68ꢀ
62ꢀ
80ꢀ
98ꢀ
Pd/resinꢀ
Au/resinꢀ
AuPd
2
/resinꢀ
4ꢀ
5ꢀ
Au
4
Au
6
Au
6
Pd/resinꢀ
Pd/resinꢀ
Pd/resinꢀ
6
aꢀ
cꢀ
Reactionꢀconditions:ꢀ1ꢀmmolꢀ1a,ꢀ0.5ꢀmmolꢀ1b,ꢀ2ꢀmmolꢀKOH,ꢀcatalystꢀ(1ꢀ
3.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
bꢀ
2
mol%),ꢀ2ꢀmLꢀH O,ꢀP(O
2
)=0.1ꢀMPaꢀ,ꢀ60ꢀ°C,ꢀ6ꢀh.ꢀ DeterminedꢀbyꢀGCꢀusingꢀ
n‐dodecaneꢀasꢀanꢀinternalꢀstandardꢀandꢀcalculatedꢀbasedꢀonꢀ1b.ꢀInꢀallꢀ
experiments,ꢀ 1aꢀ wereꢀ totallyꢀ converted,ꢀ andꢀ theꢀ correspondingꢀ
by‐productꢀwasꢀbenzoicꢀacid.ꢀ ꢀ3mol%ꢀcatalyst,ꢀ1.5ꢀmmolꢀ1a.ꢀ
3.1.ꢀ ꢀ XRDꢀandꢀSTEMꢀcharacterizationꢀresultsꢀ
c
ꢀ
Theꢀ Au/resin,ꢀ Pd/resinꢀ andꢀ Au‐Pd/resinꢀ catalystsꢀ wereꢀ
preparedꢀ withꢀ theꢀ ionꢀ exchange‐NaBH ꢀ reductionꢀ method.ꢀ
4
benzylꢀ alcoholꢀ andꢀ 1‐phenylethanolꢀ wasꢀ selectedꢀ asꢀ theꢀ testꢀ
reaction.ꢀ Theꢀ reactionꢀ wasꢀ firstꢀ conductedꢀ atꢀ 60ꢀ °Cꢀ forꢀ 6ꢀ hꢀ
STEMꢀimagesꢀ(Fig.ꢀ1(a)–(c))ꢀshowedꢀthatꢀnanoparticlesꢀwithꢀanꢀ
averageꢀsizeꢀofꢀ2–3ꢀnmꢀwereꢀhighlyꢀdispersedꢀonꢀtheꢀsupport.ꢀ
Inꢀ agreementꢀ withꢀ theꢀ STEMꢀ images,ꢀ theꢀ XRDꢀ patternsꢀ (Fig.ꢀ
underꢀ O ꢀ atmosphereꢀ inꢀ aqueousꢀ mediaꢀ toꢀ haveꢀ anꢀ
2
environmentallyꢀ benignꢀ process.ꢀ Asꢀ shownꢀ inꢀ Tableꢀ 1,ꢀ
monometallicꢀAu/resinꢀandꢀPd/resinꢀgaveꢀpoorꢀselectivityꢀforꢀ
theꢀ couplingꢀ reaction,ꢀ givingꢀ theꢀ unsaturatedꢀ chalconeꢀ withꢀ
1(d))ꢀshowedꢀbroadꢀpeaksꢀofꢀtheꢀ(111)ꢀreflection.ꢀTheꢀsizeꢀofꢀ
theꢀnanoparticlesꢀinꢀAu/resinꢀandꢀAu Pd/resinꢀsamplesꢀcalcu‐
6
latedꢀbyꢀtheꢀScherrerꢀequationꢀwasꢀ2.5ꢀnm,ꢀinꢀgoodꢀagreementꢀ
withꢀthatꢀestimatedꢀfromꢀtheꢀSTEMꢀimages.ꢀOnꢀcomparingꢀwithꢀ
monometallicꢀ Au/resinꢀ andꢀ Pd/resinꢀ catalysts,ꢀ theꢀ (111)ꢀ re‐
1
8%ꢀandꢀ11%ꢀyield,ꢀrespectively.ꢀTheꢀmainꢀsideꢀproductsꢀwereꢀ
benzoicꢀ acidꢀ andꢀ hypnoneꢀ whichꢀ cameꢀ fromꢀ theꢀ
over)oxidationꢀofꢀbenzylꢀaldoholꢀandꢀ1‐phenylethanolꢀthatꢀdidꢀ
(
flectionꢀofꢀtheꢀAu
them,ꢀ suggestingꢀ theꢀ formationꢀ ofꢀ aꢀ Au‐Pdꢀ alloyꢀ inꢀ theꢀ
Au Pd/resinꢀsampleꢀ[20–22].ꢀ
6
Pd/resinꢀwasꢀfoundꢀtoꢀbeꢀpositionedꢀbetweenꢀ
Tableꢀ2ꢀ
Substrateꢀ scopeꢀ ofꢀ theꢀ Au
cross‐couplingꢀofꢀalcohols.ꢀ ꢀ
6
Pd/resinꢀ catalystꢀ forꢀ aerobicꢀ C‒Cꢀ
6
a
O
OH
Au6Pd/resin
3.2.ꢀ ꢀ Catalyticꢀperformanceꢀ
R1 OH
+
R1
R2
R2
O balloon, KOH,
2
Toꢀ evaluateꢀ theꢀ catalysts,ꢀ aerobicꢀ C‒Cꢀ cross‐couplingꢀ ofꢀ
H2O 2mL
o
7
0 C, 6 h
Productꢀ
Molecularꢀformulaꢀ
Isolatedꢀyieldꢀ(%)
60ꢀ
80
70
60
50
40
30
20
10
0
100
80
(a)
(b)
2.3 + 0.6 nm
2
.1±0.7 nm
O
60
1ꢀ
40
20
ꢀ
O
0
0
1
2
3
4
5
6
1
2
3
4
5
6
Particle size (nm)
Partical size (nm)
2
3
ꢀ
ꢀ
71ꢀ
61ꢀ
ꢀ
O
(c)
(d)
1
40
O
2
.2 + 0.7 nm
120
Au/resin
Pd/resin
ꢀ
100
O
O
8
0
AuPd/resin
6
6
0
4
5
ꢀ
ꢀ
46ꢀ
18ꢀ
4
0
2
0
ꢀ
ꢀ
0
1
2
3
4
5
6
7
Partical size (nm)
aꢀReactionꢀconditions:ꢀprimaryꢀalcoholꢀ1.0ꢀmmol,ꢀsecondaryꢀalcoholꢀ0.5ꢀ
mmol,ꢀ2ꢀmmolꢀKOH,ꢀcatalystꢀ3ꢀmol%,ꢀ2ꢀmLꢀH O,ꢀP(O )ꢀ=ꢀ0.1ꢀMPa,ꢀ60–70
C,ꢀ6ꢀh.ꢀTheꢀyieldsꢀreferꢀtoꢀtheꢀisolatedꢀproducts.ꢀInꢀallꢀexperiments,ꢀtheꢀ
10
20
30
40
50
60
70
80
o
2
2
2
/ ( )
°
Fig.ꢀ1.ꢀSTEMꢀimagesꢀofꢀ(a)ꢀAu/resin,ꢀ(b)ꢀAu
d)ꢀXRDꢀpatternsꢀofꢀtheꢀsamples.ꢀ
6
Pd/resin,ꢀ(c)ꢀPd/resinꢀand
secondaryꢀalcoholsꢀwereꢀtotallyꢀconverted,ꢀandꢀtheꢀonlyꢀby‐productꢀwasꢀ
hypnone.ꢀ
(

ꢀ
MaoxiangꢀZhouꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1764–1770ꢀ
1767ꢀ
notꢀ undergoꢀ theꢀ cross‐couplingꢀ reaction.ꢀ Inꢀ contrast,ꢀ theꢀ
bimetallicꢀAu‐Pd/resinꢀcatalystsꢀgaveꢀaꢀsignificantlyꢀincreasedꢀ
yieldꢀ ofꢀ theꢀ productꢀ inꢀ comparisonꢀ withꢀ theꢀ monometallicꢀ
Tableꢀ4ꢀ
Controlꢀexperiment.ꢀaꢀ
O
O
Au6Pd/resin
counterparts.ꢀForꢀexample,ꢀAuPd
theꢀcouplingꢀproductsꢀofꢀ39%,ꢀwhileꢀAu
yieldꢀ ofꢀ 50%.ꢀ Theꢀ yieldꢀ reachedꢀ asꢀ highꢀ asꢀ 73%ꢀ whenꢀ theꢀ
amountꢀofꢀcatalystꢀwasꢀincreasedꢀtoꢀ3.0ꢀmol%ꢀunderꢀoptimizedꢀ
reactionꢀ conditions,ꢀ demonstratingꢀ aꢀ strongꢀ synergisticꢀ effectꢀ
betweenꢀAuꢀandꢀPd.ꢀ
Afterꢀ establishingꢀ theꢀ optimumꢀ reactionꢀ conditions,ꢀ weꢀ
addressedꢀ theꢀ issuesꢀ ofꢀ substrateꢀ scopeꢀ andꢀ functionalꢀ groupꢀ
toleranceꢀ ofꢀ theꢀ catalyticꢀ system.ꢀ Asꢀ shownꢀ inꢀ Tableꢀ 2,ꢀ theꢀ
Au‐Pd/resinꢀ catalystꢀ exhibitedꢀ goodꢀ toleranceꢀ forꢀ variousꢀ
substratesꢀ withꢀ differentꢀ functionalꢀ groups,ꢀ andꢀ moderateꢀ toꢀ
goodꢀ yieldsꢀ wereꢀ obtained.ꢀ Notably,ꢀ aliphaticꢀ alcohols,ꢀ e.g.,ꢀ
biomassꢀderivedꢀ1‐butanolꢀthatꢀareꢀusuallyꢀslowꢀtoꢀoxidize,ꢀwasꢀ
convertedꢀreadilyꢀtoꢀtheꢀproductꢀalthoughꢀrelativelyꢀlowꢀyieldsꢀ
wereꢀobtained.ꢀMoreꢀimportantly,ꢀtheꢀAu‐Pd/resinꢀcatalystꢀcanꢀ
beꢀ easilyꢀ recoveredꢀ fromꢀ theꢀ reactionꢀ systemꢀ byꢀ simpleꢀ
2
/resinꢀaffordedꢀaꢀtotalꢀyieldꢀofꢀ
OH
+
O
O2 balloon,
KOH (4.0 equiv)
H2O (2 mL),
+
6
Pd/resinꢀgaveꢀaꢀtotalꢀ
1
a
1c
1d
0 oC, 6 h
6
b
b
Entryꢀ
Catalystꢀ
Conversionꢀofꢀ1cꢀ
ꢀ
Yieldꢀofꢀ1dꢀ ꢀ(%)ꢀ
(%)ꢀ
0ꢀ
0ꢀ
1
2
3
aꢀ
ꢀ
ꢀ
ꢀ
Au/resinꢀ
Pd/resinꢀ
Pd/resinꢀ
0ꢀ
0ꢀ
92.7ꢀ
Au
6
100ꢀ
Reactionꢀconditions:ꢀ1aꢀ1.0ꢀmmol,ꢀ1cꢀ0.5ꢀmmol,ꢀKOHꢀ2.0ꢀmmol,ꢀH
2
Oꢀ2ꢀ
bꢀ
2
mL,ꢀP(O )ꢀ=ꢀ0.1ꢀMPa,ꢀcatalystꢀ1.0ꢀmol%,ꢀ60ꢀ°C,ꢀ6ꢀh.ꢀ DeterminedꢀbyꢀGCꢀ
usingꢀn‐dodecaneꢀasꢀanꢀinternalꢀstandard.ꢀ
condensationꢀ toꢀ produceꢀ α,β‐unsaturatedꢀ ketone,ꢀ whereasꢀ inꢀ
theꢀ bimetallicꢀ Au‐Pd/resinꢀ system,ꢀ hydrogenꢀ auto‐transferꢀ
occurredꢀ afterꢀ theꢀ aldolꢀ condensationꢀ reaction,ꢀ thusꢀ yieldingꢀ
theꢀ saturatedꢀ product.ꢀ Toꢀ showꢀ theꢀ transferꢀ reductionꢀ
mechanism,ꢀcontrolꢀexperimentsꢀofꢀcouplingꢀofꢀbenzylꢀalcoholꢀ
andꢀ chalconeꢀ underꢀ theꢀ sameꢀ reactionꢀ conditionsꢀ wereꢀ
conductedꢀ(Tableꢀ4).ꢀItꢀcanꢀbeꢀseenꢀthatꢀoverꢀtheꢀmonometallicꢀ
Au/resinꢀandꢀPd/resin,ꢀtheꢀchalconeꢀremainedꢀintact,ꢀwhereasꢀ
itꢀwasꢀtransformedꢀtoꢀtheꢀcorrespondingꢀsaturatedꢀketoneꢀoverꢀ
filtration.ꢀ Afterꢀ washingꢀ andꢀ drying,ꢀ theꢀ Au
Pd/resinꢀ catalystꢀ
6
wasꢀdirectlyꢀsubmittedꢀtoꢀanotherꢀcycleꢀofꢀreaction.ꢀAsꢀshownꢀ
inꢀ Tableꢀ 3,ꢀ theꢀ catalystꢀ couldꢀ beꢀ reusedꢀ forꢀ atꢀ leastꢀ 5ꢀ timesꢀ
withoutꢀ significantꢀ decreaseꢀ inꢀ productꢀ yield,ꢀ demonstratingꢀ
theꢀhighꢀstabilityꢀofꢀtheꢀAu‐Pd/resinꢀcatalyst.ꢀ
theꢀ bimetallicꢀ Au
Pd/resinꢀ catalyst.ꢀ Thisꢀ confirmedꢀ thatꢀ theꢀ
hydrogenꢀ auto‐transferedꢀ indeedꢀ occurredꢀ onꢀ theꢀ bimetallicꢀ
Au‐Pd/resinꢀsystem.ꢀ
6
3.3.ꢀ ꢀ Reactionꢀmechanismꢀ
Toꢀunderstandꢀhowꢀtheꢀtransferredꢀhydrogenationꢀoccurredꢀ
onꢀ theꢀ bimetallicꢀ Au‐Pd/resinꢀ catalyst,ꢀ weꢀ thenꢀ performedꢀ
XAFSꢀ characterizationsꢀ toꢀ determineꢀ theꢀ valenceꢀ stateꢀ ofꢀ Auꢀ
andꢀPdꢀinꢀtheꢀcatalyst.ꢀFig.ꢀ2ꢀshowsꢀtheꢀXANESꢀspectraꢀatꢀtheꢀPdꢀ
K‐edgeꢀofꢀtheꢀAu‐Pd/resinꢀcatalystsꢀasꢀwellꢀasꢀofꢀtheꢀreferenceꢀ
samples.ꢀTheꢀE
withꢀanꢀincreaseꢀofꢀtheꢀoxidationꢀstateꢀofꢀPdꢀ[24],ꢀfollowedꢀtheꢀ
orderꢀofꢀPdꢀfoilꢀ<ꢀAu Pd/resinꢀ<ꢀAu Pd/resinꢀ<ꢀAuPd /resinꢀ<ꢀ
Pdꢀresinꢀ≈ꢀPdOꢀ(Fig.ꢀ2,ꢀinsetꢀandꢀFig.ꢀ3).ꢀThisꢀindicatedꢀthatꢀtheꢀ
Itꢀ isꢀ interestingꢀ toꢀ noteꢀ thatꢀ theꢀ bimetallicꢀ Au‐Pd/resinꢀ
catalystsꢀshowedꢀaꢀdistinctꢀproductꢀdistributionꢀdifferentꢀfromꢀ
theirꢀ monometallicꢀ counterparts.ꢀ Theꢀ mainꢀ productꢀ overꢀ theꢀ
Au‐Pd/resinꢀ catalystsꢀ wasꢀ theꢀ saturatedꢀ ketones.ꢀ Itꢀ isꢀ widelyꢀ
acceptedꢀ thatꢀ inꢀ theꢀ couplingꢀ reactionsꢀ ofꢀ primaryꢀ andꢀ
secondaryꢀ alcoholsꢀ theꢀ substratesꢀ areꢀ firstꢀ convertedꢀ toꢀ theꢀ
aldehydeꢀandꢀketones,ꢀwhichꢀthenꢀundergoꢀaldolꢀcondensationꢀ
reactionꢀ underꢀ basicꢀ conditionsꢀ toꢀ yieldꢀ theꢀ unsaturatedꢀ
ketones.ꢀ Whenꢀ underꢀ inertꢀ orꢀ reducedꢀ conditions,ꢀ thisꢀ isꢀ
followedꢀ byꢀ hydrogenationꢀ toꢀ yieldꢀ theꢀ saturatedꢀ productsꢀ
0
ꢀvaluesꢀofꢀtheꢀcatalysts,ꢀwhichꢀusuallyꢀincreaseꢀ
6
4
2
Pdꢀ componentꢀ inꢀ theꢀ Au
6
Pdꢀ catalystꢀ wasꢀ mainlyꢀ inꢀ metallicꢀ
0
stateꢀ (Pd ).ꢀ Inꢀ otherꢀ words,ꢀ Pdꢀ becameꢀ moreꢀ resistantꢀ toꢀ
oxidationꢀ whenꢀ alloyedꢀ withꢀ Au,ꢀ whichꢀ wasꢀ furtherꢀ
demonstratedꢀbyꢀtheꢀEXAFSꢀfittingꢀresults.ꢀAsꢀshownꢀinꢀTableꢀ5,ꢀ
PdꢀwasꢀtotallyꢀoxidizedꢀtoꢀPdOꢀinꢀtheꢀPd/resinꢀsampleꢀwhenꢀitꢀ
wasꢀstoredꢀatꢀambientꢀconditionsꢀforꢀaꢀlongꢀtime.ꢀHowever,ꢀtheꢀ
[12,23].ꢀBasedꢀonꢀthisꢀreactionꢀmechanism,ꢀweꢀenvisionꢀthatꢀinꢀ
theꢀ caseꢀ ofꢀ theꢀ monometallicꢀ Au/resinꢀ andꢀ Pd/resin,ꢀ theꢀ
alcoholsꢀ underwentꢀ sequentialꢀ aerobicꢀ oxidation‐aldolꢀ
Tableꢀ3ꢀ
Recoveryꢀ andꢀ reuseꢀ ofꢀ Au
alcohols.ꢀ
6
Pd/resinꢀ forꢀ theꢀ C‒Cꢀ cross‐couplingꢀ ofꢀ
aꢀ
Reuseꢀ
Yieldꢀ(%)ꢀ
70ꢀ
1
2
3
4
5
stꢀ
ndꢀ
rdꢀ
thꢀ
thꢀ
54ꢀ
68ꢀ
59ꢀ
57ꢀ
aꢀReactionꢀconditions:ꢀ1.5ꢀmmolꢀ1a,ꢀ0.5ꢀmmolꢀ1b,ꢀ2ꢀmmolꢀKOH,ꢀcatalystꢀ
ꢀmol%,ꢀ2ꢀmLꢀH O,ꢀP(O )ꢀ=ꢀ0.1ꢀMPa,ꢀ60ꢀ°C,ꢀ6ꢀh.ꢀYieldꢀwasꢀdeterminedꢀbyꢀ
GCꢀusingꢀn‐dodecaneꢀasꢀanꢀinternalꢀstandardꢀandꢀcalculatedꢀbasedꢀonꢀ
b.ꢀ
3
2
2
Fig.ꢀ2.ꢀNormalizedꢀXANESꢀspectraꢀatꢀPdꢀK‐edgeꢀforꢀdifferentꢀsamples.ꢀ
1
InsetꢀshowsꢀtheꢀE ꢀshiftꢀofꢀdifferentꢀsamples.ꢀ
0

1768ꢀ
MaoxiangꢀZhouꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1764–1770ꢀ
theꢀ Pd(0)ꢀ catalystꢀ [25].ꢀ Similarly,ꢀ theꢀ Pd(0)ꢀ sitesꢀ inꢀ ourꢀ
Au
Pd/resinꢀ catalystꢀ probablyꢀ canꢀ abstractꢀ theꢀ β‐C‐Hꢀ ofꢀ
6
alcoholsꢀtoꢀformꢀaꢀPd‐Hꢀspecies,ꢀwhichꢀwouldꢀbeꢀtheꢀsourceꢀofꢀ
hydrogenꢀ inꢀ theꢀ auto‐transferredꢀ hydrogenationꢀ reaction.ꢀ
However,ꢀ underꢀ ourꢀ aerobicꢀ oxidativeꢀ conditions,ꢀ theꢀ
super‐oxoꢀspeciesꢀactivatedꢀonꢀAuꢀsitesꢀcanꢀalsoꢀdissociateꢀtheꢀ
β‐C‐Hꢀbond.ꢀGivenꢀtheꢀsimilarꢀroleꢀofꢀtheꢀsuper‐oxoꢀspeciesꢀandꢀ
Pd(0)ꢀ sitesꢀ inꢀ theꢀ reaction,ꢀ aꢀ contradictionꢀ wouldꢀ be:ꢀ (1)ꢀ ifꢀ
Pd(0)ꢀsitesꢀwereꢀresponsibleꢀforꢀtheꢀabstractionꢀofꢀtheꢀβ‐C‐Hꢀofꢀ
alcohols,ꢀ theꢀ couplingꢀ reactionꢀ ofꢀ primaryꢀ andꢀ secondaryꢀ
alcoholsꢀ wouldꢀ readilyꢀ occurꢀ underꢀ inertꢀ atmosphereꢀ
conditions,ꢀ whereasꢀ ourꢀ controlꢀ experimentꢀ resultsꢀ showedꢀ
thatꢀ noꢀ anyꢀ couplingꢀ productsꢀ wasꢀ detected;ꢀ (2)ꢀ ifꢀ theꢀ
super‐oxoꢀ speciesꢀ contributedꢀ toꢀ theꢀ dissociationꢀ ofꢀ β‐C‐Hꢀ
bond,ꢀthenꢀtheꢀauto‐transferꢀhydrogenationꢀreactionꢀwouldꢀnotꢀ
occurꢀbecauseꢀofꢀtheꢀtransformationꢀofꢀtheꢀβ‐HꢀtoꢀH
O.ꢀ
2
Toꢀ gainꢀ moreꢀ insightꢀ intoꢀ theꢀ reactionꢀ mechanismꢀ andꢀ
discriminateꢀ betweenꢀ theꢀ roleꢀ ofꢀ theꢀ super‐oxoꢀ speciesꢀ andꢀ
Pd(0)ꢀ sitesꢀ inꢀ theꢀ reaction,ꢀ anotherꢀ controlꢀ experimentꢀ ofꢀ
Fig.ꢀ3.ꢀTheꢀXANESꢀspectraꢀatꢀPdꢀLIII‐edgeꢀofꢀPd/resinꢀandꢀdifferentꢀAu‐
Pd/resin.ꢀ
Au
‐phenylethanolꢀ underꢀ anꢀ inertꢀ atmosphereꢀ conditionꢀ wasꢀ
performed.ꢀBenzylꢀalcoholꢀwasꢀsmoothlyꢀconvertedꢀtoꢀbenzoicꢀ
acidꢀ withꢀ aꢀ GCꢀ yieldꢀ ofꢀ 23.1%ꢀ overꢀ Au Pd/resinꢀ underꢀ Ar,ꢀ
whereasꢀ 1‐phenylethanolꢀ remainedꢀ intact.ꢀ Theꢀ resultsꢀ
suggestedꢀ thatꢀ forꢀ primaryꢀ alcoholsꢀ thatꢀ areꢀ usuallyꢀ easilyꢀ
6
Pd/resinꢀ catalysedꢀ transformationꢀ ofꢀ benzylꢀ alcoholꢀ andꢀ
1
Tableꢀ5ꢀ
EXAFSꢀ dataꢀ fittingꢀ resultsꢀ ofꢀ Au‐Pd/resin,ꢀ Au/resinꢀ andꢀ Pd/resinꢀ
6
aꢀ
catalysts.ꢀ
2
3
Sampleꢀ
Scatterꢀ
Au‐Auꢀ
Au‐Auꢀ
Au‐Pdꢀ
Pd‐Auꢀ
Pd‐Oꢀ
Au‐Auꢀ
Au‐Pdꢀ
Pd‐Pdꢀ
Pd‐Auꢀ
Pd‐Oꢀ
Nꢀ
R/nmꢀ  ꢀ(10 ) ΔE0ꢀ(eV)
Au/resinꢀ
7.9ꢀ
8.2ꢀ
1.1ꢀ
5.0ꢀ
1.4ꢀ
8.0ꢀ
1.4ꢀ
0.9ꢀ
5.2ꢀ
1.8ꢀ
6.0ꢀ
4.0ꢀ
3.7ꢀ
4.0ꢀ
0.282ꢀ
0.281ꢀ
0.279ꢀ
0.279ꢀ
0.200ꢀ
0.280ꢀ
0.272ꢀ
0.278ꢀ
0.280ꢀ
0.204ꢀ
0.280ꢀ
0.276ꢀ
0.204ꢀ
0.204ꢀ
2.0ꢀ
1.0ꢀ
1.15ꢀ
0.88ꢀ
0.15ꢀ
1.5ꢀ
1.5ꢀ
2.0ꢀ
2.0ꢀ
3.0ꢀ
1.5ꢀ
1.5ꢀ
3.0ꢀ
3.0ꢀ
–0.8ꢀ
3.0ꢀ
3.0ꢀ
–4.4ꢀ
–4.4ꢀ
–1.7ꢀ
3.7ꢀ
oxidised,ꢀ theꢀ Pd(0)ꢀ sitesꢀ inꢀ Au Pd/resinꢀ canꢀ directlyꢀ abstractꢀ
6
6
Au Pd/resinꢀ
theꢀ β‐C‐Hꢀ withoutꢀ theꢀ assistanceꢀ ofꢀ oxygen,ꢀ whereasꢀ forꢀ
secondaryꢀ alcoholsꢀ whichꢀ areꢀ moreꢀ difficultꢀ toꢀ transform,ꢀ
oxygenꢀisꢀneededꢀforꢀtheꢀdissociationꢀofꢀtheꢀβ‐C‐Hꢀbond.ꢀ ꢀ
Basedꢀ onꢀ theꢀ controlꢀ experimentsꢀ andꢀ characterizationꢀ
results,ꢀaꢀreactionꢀmechanismꢀofꢀhydrogenꢀauto‐transferꢀinꢀtheꢀ
couplingꢀ reactionsꢀ ofꢀ primaryꢀ andꢀ secondaryꢀ alcoholsꢀ onꢀ theꢀ
4
Au Pd/resinꢀ
–5.2ꢀ
–3.8ꢀ
–1.7ꢀ
–1.9ꢀ
4.6ꢀ
bimetallicꢀAu Pd/resinꢀcatalystꢀwasꢀproposedꢀ(Fig.ꢀ4).ꢀFirst,ꢀtheꢀ
6
metallicꢀ Pdꢀ sitesꢀ onꢀ Au‐Pdꢀ alloysꢀ abstractꢀ theꢀ β‐Hꢀ inꢀ theꢀ
primaryꢀ alcoholsꢀ toꢀ fromꢀ Pd‐Hꢀ species,ꢀ andꢀ theꢀ alcoholsꢀ areꢀ
convertedꢀ toꢀ theꢀ correspondingꢀ aldehydes.ꢀ Theꢀ super‐oxoꢀ
speciesꢀonꢀtheꢀAuꢀsitesꢀreadilyꢀdissociateꢀtheꢀβ‐C‐Hꢀbondꢀinꢀtheꢀ
secondaryꢀalcohols,ꢀandꢀketoneꢀisꢀthenꢀproduced.ꢀSecond,ꢀtheꢀ
2
AuPd /resinꢀ
Au‐Auꢀ
Au‐Pdꢀ
Pd‐Oꢀ
–0.3ꢀ
–0.1ꢀ
Pd/resinꢀ
Pd‐Oꢀ
aꢀ
N—theꢀ coordinationꢀ numberꢀ forꢀ theꢀ absorber‐backscattererꢀ pair.ꢀ
2
R—theꢀaverageꢀabsorberꢀbackscattererꢀdistance.ꢀσ —theꢀDebyeꢀWallerꢀ
0
factor.ꢀΔE －theꢀinnerꢀpotentialꢀcorrection.ꢀ
0
proportionꢀofꢀPd ꢀ(coordinationꢀnumberꢀofꢀPd‐AuꢀandꢀPd‐Pd)ꢀ
increasedꢀ inꢀ theꢀ bimetallicꢀ Au‐Pd/resinꢀ samplesꢀ withꢀ anꢀ
increaseꢀ ofꢀ Au/Pdꢀ ratio.ꢀ Basedꢀ onꢀ theseꢀ results,ꢀ itꢀ wasꢀ
concludedꢀthatꢀtheꢀformingꢀofꢀanꢀalloyꢀwithꢀAuꢀpreventedꢀtheꢀ
oxidationꢀ ofꢀ Pdꢀ andꢀ allowedꢀ Pdꢀ toꢀ keepꢀ itsꢀ metallicꢀ state.ꢀ
Interestingly,ꢀinꢀallꢀofꢀtheꢀsamplesꢀinvestigated,ꢀAuꢀalwaysꢀkeptꢀ
itsꢀ metallicꢀ state.ꢀ Asꢀ mentionedꢀ before,ꢀ theꢀ productsꢀ overꢀ
Au/resinꢀ wasꢀ anꢀ unsaturatedꢀ ketone.ꢀ Therefore,ꢀ weꢀ canꢀ
excludeꢀtheꢀpossibilityꢀthatꢀtheꢀtransferredꢀreductionꢀoccurredꢀ
onꢀ Auꢀ sites.ꢀ Takenꢀ together,ꢀ theꢀ metallicꢀ Pdꢀ sitesꢀ onꢀ theꢀ
Au‐Pd/resinꢀcatalystsꢀwereꢀbelievedꢀtoꢀbeꢀresponsibleꢀforꢀtheꢀ
auto‐transferredꢀhydrogenationꢀreaction.ꢀ
ItꢀisꢀwellꢀknownꢀthatꢀinꢀtheꢀPdꢀcatalysedꢀoxidationꢀreactionꢀ
ofꢀalcohols,ꢀtheꢀabstractionꢀofꢀβ‐H,ꢀwhichꢀisꢀusuallyꢀregardedꢀasꢀ
theꢀrateꢀdeterminingꢀstepꢀinꢀtheꢀreaction,ꢀcanꢀdirectlyꢀoccurꢀonꢀ
Fig.ꢀ4.ꢀProposedꢀreactionꢀmechanismꢀofꢀhydrogenꢀauto‐transferꢀinꢀtheꢀ
aerobicꢀC‒Cꢀcross‐couplingꢀofꢀalcohols.ꢀ

ꢀ
MaoxiangꢀZhouꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1764–1770ꢀ
1769ꢀ
aldehydeꢀandꢀketoneꢀundergoꢀaldolꢀcondensationꢀcatalysedꢀbyꢀ
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ofꢀ Chinaꢀ (21373206,ꢀ 21202163,ꢀ 21303194,ꢀ 21476227,ꢀ
21503219)ꢀforꢀtheꢀfinancialꢀsupports.ꢀJTMꢀwasꢀfundedꢀbyꢀtheꢀ
U.S.ꢀ Departmentꢀ ofꢀ Energy,ꢀ Officeꢀ ofꢀ Basicꢀ Energyꢀ Sciences,ꢀ
Chemicalꢀ Sciencesꢀ underꢀ Contractꢀ DE‐AC‐02‐06CH11357.ꢀ Useꢀ
ofꢀ theꢀ Advancedꢀ Photonꢀ Sourceꢀ isꢀ supportedꢀ byꢀ theꢀ U.S.ꢀ De‐
partmentꢀofꢀEnergy,ꢀOfficeꢀofꢀScience,ꢀandꢀOfficeꢀofꢀBasicꢀEnergyꢀ
Sciences,ꢀunderꢀContractꢀDE‐AC02‐06CH11357.ꢀMRCATꢀopera‐
tionsꢀ areꢀ supportedꢀ byꢀ theꢀ Departmentꢀ ofꢀ Energyꢀ andꢀ theꢀ
MRCATꢀmemberꢀinstitutions.ꢀWeꢀalsoꢀthankꢀtheꢀBLꢀ14Wꢀatꢀtheꢀ
Shanghaiꢀ Synchrotronꢀ Radiationꢀ Facilityꢀ (SSRF)ꢀ forꢀ theꢀ XAFSꢀ
experiments.ꢀ
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[
2
GraphicalꢀAbstractꢀ
Chin.ꢀJ.ꢀCatal.,ꢀ2016,ꢀ37:ꢀ1764–1770ꢀ ꢀ ꢀ doi:ꢀ10.1016/S1872‐2067(16)62511‐1
Hydrogenꢀauto‐transferꢀunderꢀaerobicꢀoxidativeꢀconditions:ꢀEfficientꢀ
synthesisꢀofꢀsaturatedꢀketonesꢀbyꢀaerobicꢀC‒Cꢀcross‐couplingꢀofꢀ ꢀ
primaryꢀandꢀsecondaryꢀalcoholsꢀcatalyzedꢀbyꢀaꢀAu Pd/resinꢀcatalystꢀ
6
MaoxiangꢀZhou,ꢀLeileiꢀZhang,ꢀJeffreyꢀT.ꢀMiller,ꢀXiaofengꢀYang,ꢀXiaoyanꢀLiu,ꢀ
AiqinꢀWangꢀ*,ꢀTaoꢀZhangꢀ*ꢀ ꢀ ꢀ
DalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences,ꢀChina;ꢀUni‐
versityꢀofꢀChineseꢀAcademyꢀofꢀSciences,ꢀChina;ꢀArgonneꢀNationalꢀLaboratory,ꢀ
USAꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Aerobicꢀ C‒Cꢀ cross‐couplingꢀ ofꢀ primaryꢀ andꢀ secondaryꢀ alcoholsꢀ wasꢀ cata‐
lyzedꢀbyꢀAu Pd/resinꢀunderꢀmildꢀconditions.ꢀ
6

1770ꢀ
MaoxiangꢀZhouꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ1764–1770ꢀ
[
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