Coupling of epoxides and carbon dioxide catalyzed by Br?nsted acid ionic liquids

Article abstract of DOI:10.1016/S1872-2067(14)60227-8

A series of Br?nsted acid ionic liquids (BAILs) containing a long chain Br?nsted acid site in the cationic part and a Lewis basic site in the anionic part were designed, synthesized, and used as catalyst for the coupling of epoxides and carbon dioxide to cyclic carbonates without a co-catalyst or co-solvent. The effects of catalyst structure and other parameters on the catalytic performance were investigated. The long chain 2-(N,N-dimethyldodecylammonium) acetic acid bromide ([(CH₂COOH)DMDA]Br) showed high catalytic activity and good reusability. This protocol was expanded to various epoxides, which gave the corresponding cyclic carbonates in good yields. The acidity of the catalyst influenced its catalytic activity.

Full text of DOI:10.1016/S1872-2067(14)60227-8

ChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ408–413
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
ava i l a b l e a t w w w. s c i e n c ed 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
CouplingꢀofꢀepoxidesꢀandꢀcarbonꢀdioxideꢀcatalyzedꢀbyꢀBrönstedꢀacidꢀ
ionicꢀliquidsꢀ
ꢀa,
ꢀa ꢀ
ꢀa ꢀ
ꢀa
ꢀa ꢀ
ꢀb,#
TaoꢀChang *,ꢀXiaoruiꢀGao ,LiꢀBian ,XiyingꢀFu ,ꢀMingxiaꢀYuan ,HuanwangꢀJing
ꢀ
a
ꢀ
EngineeringꢀLaboratoryꢀforꢀCoalbedꢀGasꢀExploitationꢀofꢀHebeiꢀProvince,ꢀCollegeꢀofꢀScience,ꢀHebeiꢀUniversityꢀofꢀEngineering,ꢀHandanꢀ056038,ꢀHebei,ꢀ ꢀ
Chinaꢀ
bꢀStateꢀKeyꢀLaboratoryꢀofꢀAppliedꢀOrganicꢀChemistry,ꢀCollegeꢀofꢀChemistryꢀandꢀChemicalꢀEngineering,ꢀLanzhouꢀUniversity,ꢀLanzhouꢀ730000,ꢀGansu,ꢀChinaꢀ ꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
AꢀseriesꢀofꢀBrönstedꢀacidꢀionicꢀliquidsꢀ(BAILs)ꢀcontainingꢀaꢀlongꢀchainꢀBrönstedꢀacidꢀsiteꢀinꢀtheꢀcati‐
onicꢀpartꢀandꢀaꢀLewisꢀbasicꢀsiteꢀinꢀtheꢀanionicꢀpartꢀwereꢀdesigned,ꢀsynthesized,ꢀandꢀusedꢀasꢀcatalystꢀ
forꢀ theꢀ couplingꢀ ofꢀ epoxidesꢀ andꢀ carbonꢀ dioxideꢀ toꢀ cyclicꢀ carbonatesꢀ withoutꢀ aꢀ co‐catalystꢀ orꢀ
co‐solvent.ꢀTheꢀeffectsꢀofꢀcatalystꢀstructureꢀandꢀotherꢀparametersꢀonꢀtheꢀcatalyticꢀperformanceꢀwereꢀ
investigated.ꢀ Theꢀ longꢀ chainꢀ 2‐(N,N‐dimethyldodecylammonium)ꢀ aceticꢀ acidꢀ bromideꢀ
Receivedꢀ11ꢀAugustꢀ2014ꢀ
Acceptedꢀ15ꢀSeptemberꢀ2014ꢀ
Publishedꢀ20ꢀMarchꢀ2015ꢀ
(
[(CH COOH)DMDA]Br)ꢀshowedꢀhighꢀcatalyticꢀactivityꢀandꢀgoodꢀreusability.ꢀThisꢀprotocolꢀwasꢀex‐
2
Keywords:ꢀ
pandedꢀtoꢀvariousꢀepoxides,ꢀwhichꢀgaveꢀtheꢀcorrespondingꢀcyclicꢀcarbonatesꢀinꢀgoodꢀyields.ꢀTheꢀ
acidityꢀofꢀtheꢀcatalystꢀinfluencedꢀitsꢀcatalyticꢀactivity.ꢀ
Carbonꢀdioxideꢀfixationꢀ
Couplingꢀreactionꢀ
Brönstedꢀacidicꢀionicꢀliquidꢀ
Cyclicꢀcarbonateꢀ
©ꢀ2015,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
Hammettꢀacidity
1.ꢀ ꢀ Introductionꢀ
drogenꢀbondingꢀbetweenꢀtheꢀcatalystꢀandꢀepoxideꢀmayꢀbeꢀtheꢀ
keyꢀ factorꢀ inꢀ theꢀ couplingꢀ ofꢀ epoxidesꢀ andꢀ CO .ꢀ However,ꢀ
2
Carbonꢀ dioxideꢀ fixationꢀ isꢀ aꢀ veryꢀ activeꢀ researchꢀ areaꢀ be‐
Brönstedꢀ acidꢀ ionicꢀ liquidsꢀ (BAILs)ꢀ withꢀ imidazoliumꢀ asꢀ theꢀ
cationꢀareꢀexpensive,ꢀwhichꢀhinderedꢀtheirꢀindustrialꢀapplica‐
causeꢀ ofꢀ theꢀ greenhouseꢀ effectꢀ [1].ꢀ Anꢀ importantꢀ productꢀ ofꢀ
carbonꢀdioxideꢀfixationꢀisꢀaꢀcyclicꢀcarbonate,ꢀwhichꢀhasꢀbroadꢀ
applicationsꢀinꢀpolycarbonateꢀsynthesis,ꢀpharmaceuticalꢀinter‐
mediates,ꢀ andꢀ aproticꢀ solventsꢀ [2–4].ꢀ Manyꢀ catalystsꢀ forꢀ theꢀ
synthesisꢀofꢀcyclicꢀcarbonatesꢀhaveꢀbeenꢀdeveloped,ꢀincludingꢀ
tion.ꢀ Furthermore,ꢀ theꢀ commonlyꢀ usedꢀ dialkylimidazolium‐
ꢀ
basedꢀionicꢀliquidsꢀshowedꢀnegligibleꢀbiodegradability.ꢀThus,ꢀitꢀ
isꢀnecessaryꢀtoꢀsynthesizeꢀaꢀlessꢀexpensiveꢀionicꢀliquid.ꢀMean‐
while,ꢀtheꢀfactorsꢀsuchꢀasꢀtheꢀstructureꢀandꢀacidityꢀofꢀtheꢀcata‐
lystꢀhaveꢀnotꢀbeenꢀstudiedꢀwell.ꢀItꢀwasꢀreportedꢀinꢀourꢀpreviousꢀ
reportsꢀthatꢀtheꢀstructureꢀofꢀtheꢀionicꢀliquidꢀhasꢀanꢀimportantꢀ
influenceꢀonꢀtheꢀcatalyticꢀactivityꢀ[38–40].ꢀHere,ꢀseveralꢀnovelꢀ
longꢀchainꢀBAILsꢀfunctionalizedꢀwithꢀaꢀcarboxylꢀgroupꢀ(Schemeꢀ
1)ꢀ wereꢀ synthesized.ꢀ Aꢀ detailedꢀ studyꢀ ofꢀ theꢀ effectsꢀ ofꢀ alkylꢀ
chainꢀlengthꢀandꢀnucleophilicityꢀofꢀtheꢀanionꢀ onꢀtheꢀcouplingꢀ
reactionꢀandꢀrecycleꢀperformanceꢀwasꢀalsoꢀconducted.ꢀToꢀun‐
ꢀ
salenꢀ metalꢀ compoundsꢀ [5–10], metalloporphyrinsꢀ [11–13],ꢀ
andꢀothersꢀ[14–17].ꢀHowever,ꢀtheseꢀcatalystsꢀsufferꢀfromꢀlowꢀ
catalystꢀactivityꢀorꢀtheꢀneedꢀforꢀaꢀco‐solventꢀorꢀaꢀmetalꢀion.ꢀ ꢀ
Inꢀrecentꢀyears,ꢀionicꢀliquidsꢀasꢀcatalystsꢀhaveꢀgainedꢀmuchꢀ
interestꢀ [18–28].ꢀ Someꢀ literatureꢀ reportsꢀ demonstratedꢀ thatꢀ
hydrogenꢀbondingꢀcanꢀactivateꢀanꢀepoxideꢀandꢀallowꢀitsꢀcou‐
plingꢀ reactionꢀ [29–37].ꢀ Theseꢀ investigationsꢀ impliedꢀ thatꢀ hy‐
*Correspondingꢀauthor.ꢀTel:ꢀ+86‐310‐8578760;ꢀFax:ꢀ+86‐310‐6025698;ꢀE‐mail:ꢀchangt03@sina.comꢀ ꢀ ꢀ
ꢀ
#
ꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+86‐931‐8912585;ꢀFax:ꢀ+86‐931‐8912582;ꢀE‐mail:ꢀhwjing@lzu.edu.cnꢀ
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀNaturalꢀScienceꢀFoundationꢀofꢀHebeiꢀProvinceꢀ(B2012402001)ꢀandꢀtheꢀNationalꢀNaturalꢀScienceꢀFoundationꢀofꢀChinaꢀ
51202054,ꢀ21173106).ꢀ ꢀ
DOI:ꢀ10.1016/S1872‐2067(14)60227‐8ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ36,ꢀNo.ꢀ3,ꢀMarchꢀ2015ꢀ ꢀ ꢀ
(

ꢀ
TaoꢀChangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ408–413ꢀ
409ꢀ
1
CH
NMRꢀ(125ꢀM,ꢀD
forꢀC
(CH
3
CH
2
–),ꢀ3.36–3.40ꢀ(m,ꢀ6H,ꢀCH
2
N),ꢀ3.89ꢀ(s,ꢀ2H,ꢀNCH
2
COOH);ꢀ Cꢀ
2
O):ꢀδꢀ=ꢀ7.02,ꢀ54.20,ꢀ55.37,ꢀ167.34;ꢀESI‐MS:ꢀcalcdꢀ
+
8
H
18NO
2
Brꢀm/zꢀ[M] ꢀ=ꢀ160.2,ꢀfoundꢀ160.3.ꢀ
[
2
COOH)DMBA]Brꢀ (3).ꢀ mpꢀ 156–158ꢀ °C,ꢀ yieldꢀ 90%,ꢀ aꢀ
1
whiteꢀsolid;ꢀ HꢀNMRꢀ(500ꢀM,ꢀD
2
O):ꢀδꢀ=ꢀ0.76ꢀ(dd,ꢀJꢀ=ꢀ7.5ꢀHz,ꢀ3H,ꢀ
CH CH CH N),ꢀ 1.53–1.69ꢀ (m,ꢀ
N),ꢀ3.07ꢀ(s,ꢀ6H,ꢀNCH ),ꢀ3.86ꢀ(dd,ꢀJꢀ=ꢀ8.5ꢀHz,ꢀ
N),ꢀ3.97ꢀ(s,ꢀ2H,ꢀNCH O):ꢀ
COOH);ꢀ ꢀ 1CꢀNMRꢀ(125ꢀM,ꢀD
CH
2
2
3
CH
H,ꢀCH
H,ꢀCH
2
–),ꢀ 1.16–1.23ꢀ (m,ꢀ 2H,ꢀ CH
CH CH CH
CH
3
2
2
2
3
2
2
2
3
2
2
2
2
δꢀ=ꢀ12.91,ꢀ19.11,ꢀ24.13,ꢀ51.57,ꢀ65.41,ꢀ167.50;ꢀESI‐MS:ꢀcalcdꢀforꢀ
+
C H
8
18NO
2
Brꢀm/zꢀ[M] ꢀ=ꢀ160.2,ꢀfoundꢀ160.3.ꢀ
[
(CH
2
COOH)DMOA]Brꢀ (4).ꢀ mpꢀ 134–135ꢀ °C,ꢀ yieldꢀ 92%,ꢀ aꢀ
1
whiteꢀsolid;ꢀ HꢀNMRꢀ(500ꢀM,ꢀD
2
O):ꢀδꢀ=ꢀ0.68ꢀ(dd,ꢀJꢀ=ꢀ7.0ꢀHz,ꢀ3H,ꢀ
(CH CH CH N),ꢀ1.59ꢀ(dd,ꢀJꢀ=ꢀ
),ꢀ 3.34–3.37ꢀ (m,ꢀ 2H,ꢀ
O):ꢀδꢀ=ꢀ
CH
.5ꢀ Hz,ꢀ 2H,ꢀ –CH
CH CH
3
CH
2
–),ꢀ1.10–1.18ꢀ(m,ꢀ10H,ꢀCH
3
)
2 5
2
2
8
2
CH
2
N),ꢀ 3.07ꢀ (s,ꢀ 6H,ꢀ NCH
3
1
2
2
N),ꢀ3.99ꢀ(s,ꢀ2H,ꢀNCH
2
COOH);ꢀ CꢀNMRꢀ(125ꢀM,ꢀD
2
1
3.64,ꢀ22.22,ꢀ25.58,ꢀ28.36,ꢀ31.20,ꢀ51.71,ꢀ65.37,ꢀ167.21;ꢀESI‐MS:ꢀ
Schemeꢀ1.ꢀStructureꢀofꢀtheꢀBrӧnstedꢀacidꢀionicꢀliquidsꢀ(BAILs).ꢀ
+
calcdꢀforꢀC12
2
H26NO Brꢀm/zꢀ[M] ꢀ=ꢀ216.3,ꢀfoundꢀ216.3.ꢀ
[
(CH
2
COOH)DMDA]Brꢀ (5a).ꢀ mpꢀ 140–141ꢀ °C,ꢀ yieldꢀ 95%,ꢀ aꢀ
1
derstandꢀ theꢀ relationshipꢀ betweenꢀ acidityꢀ andꢀ activity,ꢀ theꢀ
HammettꢀmethodꢀwasꢀusedꢀtoꢀevaluateꢀtheꢀacidityꢀofꢀtheꢀBAILs.ꢀ
whiteꢀsolid;ꢀ HꢀNMRꢀ(500ꢀM,ꢀD
2
O):ꢀδꢀ=ꢀ0.70ꢀ(d,ꢀ3H,ꢀCH
N),ꢀ1.59ꢀ(s,ꢀ2H,ꢀ–CH CH N),ꢀ3.11ꢀ
CH N),ꢀ3.92ꢀ(s,ꢀ2H,ꢀNCH COOH);ꢀ
O):ꢀ δꢀ =ꢀ 14.01,ꢀ 22.72,ꢀ 22.82,ꢀ 26.41,ꢀ 29.30,ꢀ
9.69,ꢀ29.81,ꢀ29.90,ꢀ30.00,ꢀ 30.07,ꢀ32.16,ꢀ52.12,ꢀ63.96,ꢀ167.50;ꢀ
3 2
CH –),ꢀ
1.16ꢀ(d,ꢀ20H,ꢀCH
s,ꢀ6H,ꢀNCH ),ꢀ3.47ꢀ(m,ꢀ2H,ꢀCH
1Cꢀ NMRꢀ (125ꢀ M,ꢀ D
(CH )10CH CH
3 2 2 2
2
2
(
3
2
2
2
2.ꢀ ꢀ Experimentalꢀ
2
2
+
ꢀ
2.1.ꢀ ꢀ Reagentsꢀandꢀanalysisꢀ
ESI‐MS:ꢀcalcdꢀforꢀC16
H
34NO Brꢀm/zꢀ[M] ꢀ=ꢀ272.4,ꢀfoundꢀ272.4.
2
[
(CH
2
COOH)DMDA]Clꢀ (5b).ꢀ mpꢀ 150–152ꢀ °C,ꢀ yieldꢀ 95%,ꢀ aꢀ
1
1
‐Methylimidazoleꢀ (99%),ꢀ triethylamine,ꢀ N,N‐
ꢀ
dimethyl‐
whiteꢀsolid;ꢀ HꢀNMRꢀ(500ꢀM,ꢀD
2
O):ꢀδꢀ=ꢀ0.66ꢀ(t,ꢀ3H,ꢀCH
3
CH –),ꢀ
2
butylamineꢀ (97%),ꢀ N,N‐dimethyloctylamineꢀ (95%),ꢀ N,N‐
ꢀ
dime‐
1.12ꢀ(t,ꢀ20H,ꢀCH
(s,ꢀ6H,ꢀNCH ),ꢀ3.41ꢀ(t,ꢀ2H,ꢀCH
NMRꢀ(125ꢀM,ꢀD
3
(CH
2
)
10CH
2
CH
2
N),ꢀ1.53ꢀ(d,ꢀ2H,ꢀ–CH
2
CH
2
N),ꢀ3.06ꢀ
1
thyldodecylamine(97%),ꢀ N,N‐dimethylhexadecylamineꢀ (97%),ꢀ
p‐toluenesulfonicꢀ acidꢀ monohydrate,ꢀ 1,3‐propanesultone,ꢀ me‐
thylꢀ chloroacetate,ꢀ andꢀ methylꢀ bromoacetateꢀ wereꢀ obtainedꢀ
fromꢀAladdinꢀReagentꢀCo.ꢀ(Shanghai,ꢀChina).ꢀPropyleneꢀoxide,ꢀ
epichlorohydrin,ꢀstyreneꢀoxide,ꢀbutyleneꢀoxide,ꢀphenylꢀglycidylꢀ
ether,ꢀ andꢀ epoxyꢀ cyclohexaneꢀ wereꢀ obtainedꢀ fromꢀ Energyꢀ
Chemicalsꢀ (Shanghai,ꢀ China).ꢀ Theꢀ otherꢀ reagentsꢀ wereꢀ pur‐
chasedꢀfromꢀTianjinꢀKemioꢀFineꢀChemicalꢀInstituteꢀ(China)ꢀandꢀ
usedꢀ withoutꢀ purification.ꢀ NMRꢀ spectraꢀ wereꢀ recordedꢀ onꢀ aꢀ
Brukerꢀ 500ꢀ MHzꢀ spectrometer.ꢀ ESI‐MSꢀ wasꢀ performedꢀ onꢀ anꢀ
Esquireꢀ 6000ꢀ massꢀ spectrometer.ꢀ Theꢀ Hammettꢀ acidityꢀ ofꢀ
BAILsꢀwasꢀmeasuredꢀusingꢀaꢀPerkinElmerꢀLambdaꢀ35ꢀUV/Visꢀ
spectrometerꢀwithꢀaꢀbasicꢀindicatorꢀasꢀreportedꢀinꢀourꢀpreviousꢀ
paperꢀ [39].ꢀ Theꢀ meltingꢀ pointꢀ wasꢀ determinedꢀ onꢀ anꢀ XT‐4ꢀ
meltingꢀpointꢀapparatusꢀwithoutꢀcalibration.ꢀ ꢀ
3
2
CH
2
N),ꢀ3.91ꢀ(s,ꢀ2H,ꢀNCH
2
COOH);ꢀ Cꢀ
2
O):ꢀδꢀ=ꢀ14.01,ꢀ22.72,ꢀ22.82,ꢀ26.41,ꢀ29.30,ꢀ29.69,ꢀ
29.81,ꢀ29.90,ꢀ30.00,ꢀ30.07,ꢀ32.16,ꢀ52.12,ꢀ63.96,ꢀ167.50;ꢀESI‐MS:ꢀ
+
2
calcdꢀforꢀC16H34NO Clꢀm/zꢀ[M] ꢀ=ꢀ272.4,ꢀfoundꢀ272.4.ꢀ
1
[DDPA]Brꢀ(6).ꢀmpꢀ164–165ꢀ°C,ꢀyieldꢀ96%,ꢀaꢀwhiteꢀsolid;ꢀ Hꢀ
NMRꢀ (500ꢀ M,ꢀ D O):ꢀ δꢀ =ꢀ 0.65ꢀ (t,ꢀ 3H,ꢀ CH CH –),ꢀ 1.06ꢀ (s,ꢀ 16H,ꢀ
CH (CH CH CH CH Nꢀ ),ꢀ 1.54ꢀ (s,ꢀ 2H,ꢀ
–CH CH N),ꢀ1.94–2.00ꢀ(m,ꢀ2H,ꢀNCH CH SO H),ꢀ2.71ꢀ(t,ꢀ2H,ꢀ
NCH CH CH SO H),ꢀ2.91ꢀ(s,ꢀ6H,ꢀNCH CH N),ꢀ
3.25–3.28ꢀ(m,ꢀ2H,ꢀNCH CH CH SO H);ꢀ CꢀNMRꢀ(125ꢀM,ꢀD O):ꢀδꢀ
2
3
2
3
)
2 8
2
2
N),ꢀ1.15ꢀ (s,ꢀ 2H,ꢀ–CH
2
CH
2
2
2
2
2
CH
2
2
3
2
2
2
3
3
),ꢀ3.13ꢀ(t,ꢀ2H,ꢀ–CH
2
2
1
2
2
2
3
2
=ꢀ13.99,ꢀ18.44,ꢀ22.41,ꢀ22.79,ꢀ26.25,ꢀ29.26,ꢀ29.67,ꢀ29.76,ꢀ29.90,ꢀ
29.99,ꢀ30.04,ꢀ32.12,ꢀ47.51,ꢀ50.77,ꢀ62.22,ꢀ64.32;ꢀESI‐MS:ꢀcalcdꢀforꢀ
+
C
17
H
38NSO
3
Brꢀm/zꢀ[M] ꢀ=ꢀ336.6,ꢀfoundꢀ336.5.ꢀ
[(CH
2
COOH)DMHA]Brꢀ (7).ꢀ mpꢀ 146–147ꢀ °C,ꢀ yieldꢀ 93%,ꢀ aꢀ
1
whiteꢀsolid;ꢀ HꢀNMRꢀ(500ꢀM,ꢀDMSO):ꢀδꢀ=ꢀ0.84ꢀ(t,ꢀ3H,ꢀCH
3 2
CH –),ꢀ
1
.22ꢀ (s,ꢀ 28,ꢀ CH
2.44–2.49ꢀ(m,ꢀ6H,ꢀNCH
H,ꢀ NCH COOH);ꢀ ESI‐MS:ꢀ calcdꢀ forꢀ C20
3
(CH
2
)
14CH
),ꢀ3.21ꢀ(t,ꢀ2H,ꢀCH
2
CH
2
N),ꢀ 1.63ꢀ (s,ꢀ 2H,ꢀ –CH
2
CH
2
N),ꢀ
2.2.ꢀ ꢀ Catalystꢀpreparationꢀ
3
2 2
CH N),ꢀ3.34–3.74ꢀ(m,ꢀ
+
2
2
2
H42NO Brꢀ m/zꢀ [M] ꢀ =ꢀ
TheꢀBAILsꢀwereꢀpreparedꢀaccordingꢀtoꢀreportedꢀproceduresꢀ
328.6,ꢀfoundꢀ328.6.ꢀ
[41].ꢀAꢀtypicalꢀsynthesisꢀrouteꢀofꢀ[(CH
2
COOH)DMDA]Brꢀ(5a)ꢀisꢀ
2
asꢀ follows.ꢀ Underꢀ anꢀ inertꢀ atmosphereꢀ ofꢀ N ,ꢀ aꢀ mixtureꢀ ofꢀ
2.3.ꢀ ꢀ HammettꢀacidityꢀofꢀtheꢀBAILsꢀ
N,N‐dimethyldodecylamineꢀ (0.01ꢀ mol,ꢀ 1.27ꢀ mL)ꢀ andꢀ methylꢀ
bromoacetateꢀ(0.01ꢀmol,ꢀ0.6ꢀmL)ꢀwasꢀstirredꢀatꢀroomꢀtempera‐
tureꢀforꢀ12ꢀh,ꢀduringꢀwhichꢀtimeꢀtheꢀreactionꢀmixtureꢀturnedꢀ
Theꢀ Hammettꢀ acidityꢀ (H
equation:ꢀH ꢀ=ꢀpK(Iaq)ꢀ+ꢀlg([I]
baseꢀ indicator,ꢀ andꢀ [IH+]
ꢀandꢀ[I]
concentrationꢀofꢀtheꢀprotonatedꢀandꢀnon‐protonatedꢀformsꢀofꢀ
theꢀindicator.ꢀTheꢀvalueꢀofꢀ[I] ꢀwasꢀdeterminedꢀandꢀcal‐
/[IH+]
culatedꢀfromꢀtheꢀUV‐Visꢀspectrum.ꢀInꢀtheꢀexperiment,ꢀdimethylꢀ
yellowꢀ(pK ꢀ=ꢀ3.3)ꢀwasꢀchosenꢀasꢀtheꢀbaseꢀindicatorꢀandꢀethanolꢀ
asꢀtheꢀsolvent.ꢀTheꢀmaximumꢀabsorbanceꢀofꢀtheꢀnon‐protonat‐
0
)ꢀ functionꢀ wasꢀ calculatedꢀ byꢀ theꢀ
/[IH+]
).ꢀHere,ꢀ"I"ꢀrepresentsꢀtheꢀ
ꢀ are,ꢀ respectively,ꢀ theꢀ molarꢀ
0
s
s
intoꢀaꢀsolid.ꢀAꢀmixtureꢀofꢀtheꢀsolidꢀandꢀHClꢀ(37%ꢀH
2
Oꢀsolution,ꢀ
s
s
0.012ꢀmol)ꢀwasꢀrefluxedꢀforꢀ1ꢀh.ꢀTheꢀsolventꢀwasꢀremovedꢀun‐
derꢀvacuum,ꢀandꢀtheꢀremainingꢀsolidꢀwasꢀwashedꢀthreeꢀtimesꢀ
withꢀcoldꢀdiethylꢀetherꢀtoꢀgiveꢀtheꢀproductꢀasꢀaꢀwhiteꢀpowder.ꢀ ꢀ
s
s
[
(CH
2
COOH)TEA]Brꢀ(2).ꢀmpꢀ188–190ꢀ°C,ꢀyieldꢀ86%,ꢀaꢀwhiteꢀ
a
1
ꢀ
solid;ꢀ Hꢀ NMRꢀ (500ꢀ M,ꢀ D O):ꢀ δꢀ =ꢀ 1.12ꢀ (dd,ꢀ Jꢀ =ꢀ 7.5ꢀ Hz,ꢀ 9H,ꢀ
2

410ꢀ
TaoꢀChangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ408–413ꢀ
edꢀformꢀofꢀdimethylꢀyellowꢀwasꢀobservedꢀatꢀ432.5ꢀnmꢀinꢀetha‐
nol.ꢀWithꢀtheꢀincreaseꢀinꢀacidityꢀofꢀtheꢀBAILs,ꢀtheꢀabsorbanceꢀofꢀ
theꢀnon‐protonatedꢀformꢀofꢀtheꢀbaseꢀindicatorꢀdecreased,ꢀwhileꢀ
theꢀ protonatedꢀ formꢀ ofꢀ theꢀ indicatorꢀ couldꢀ notꢀ beꢀ observedꢀ
BAILsꢀcatalyticꢀactivityꢀforꢀtheꢀcouplingꢀreaction.ꢀTheꢀBAILꢀofꢀ6ꢀ
incorporatedꢀwithꢀaꢀsulfonicꢀacidicꢀgroupꢀinsteadꢀofꢀaꢀcarbox‐
ylicꢀ oneꢀ showedꢀ theꢀ strongestꢀ acidityꢀ (entryꢀ 7ꢀ versusꢀ entriesꢀ
2–6ꢀandꢀ8).ꢀHowever,ꢀ6ꢀexhibitedꢀtheꢀlowestꢀactivityꢀevenꢀatꢀaꢀ
highꢀtemperatureꢀ(entryꢀ7).ꢀTheꢀresultꢀimpliedꢀthatꢀmoderateꢀ
acidityꢀwasꢀbeneficialꢀforꢀtheꢀreaction.ꢀAccordingꢀtoꢀtheꢀreactionꢀ
mechanism,ꢀhydrogenꢀbondingꢀbetweenꢀtheꢀprotonꢀofꢀtheꢀcar‐
bonylꢀgroupꢀandꢀoxygenꢀofꢀtheꢀepoxideꢀhasꢀaꢀpositiveꢀeffectꢀonꢀ
activatingꢀtheꢀringꢀopeningꢀofꢀtheꢀepoxide.ꢀHowever,ꢀhydrogenꢀ
bondingꢀthatꢀisꢀtooꢀstrong,ꢀformedꢀwhenꢀtheꢀacidityꢀofꢀtheꢀionicꢀ
becauseꢀ ofꢀ itsꢀ smallꢀ molarꢀ absorptivity.ꢀ Soꢀ [I]
terminedꢀfromꢀtheꢀdifferenceꢀinꢀmeasuredꢀabsorbanceꢀafterꢀtheꢀ
additionꢀofꢀcatalyst,ꢀandꢀthenꢀH ꢀcanꢀbeꢀcalculated.ꢀ
s
/[IH+]sꢀwasꢀ de‐
0
2
.4.ꢀ ꢀ GeneralꢀprocedureꢀforꢀtheꢀcouplingꢀofꢀepoxideꢀandꢀCO
2
ꢀ ꢀ
catalyzedꢀbyꢀBAILsꢀ
liquidꢀwasꢀstrong,ꢀimpededꢀtheꢀinsertionꢀofꢀCO
ꢀintoꢀtheꢀhydro‐
2
AꢀsolutionꢀofꢀBAILꢀ(0.1ꢀmmol)ꢀinꢀepoxideꢀ(0.1ꢀmol)ꢀwasꢀin‐
troducedꢀintoꢀaꢀ100ꢀmLꢀstainlessꢀsteelꢀautoclave.ꢀItꢀwasꢀpurgedꢀ
genꢀbondꢀbetweenꢀtheꢀhydrogenꢀatomꢀandꢀoxygenꢀatomꢀ[35].ꢀ
Moreover,ꢀ weꢀ proposeꢀthatꢀtheꢀlongꢀchainꢀcatalystsꢀ5aꢀandꢀ7ꢀ
threeꢀ timesꢀ withꢀ CO
roomꢀtemperature.ꢀThen,ꢀtheꢀmixtureꢀwasꢀstirredꢀandꢀheatedꢀtoꢀ
20ꢀ°C.ꢀAfterꢀtheꢀreaction,ꢀtheꢀreactorꢀwasꢀcooledꢀandꢀvented.ꢀ
2
ꢀ andꢀ thenꢀ filledꢀ withꢀ CO
2
ꢀ toꢀ 0.9ꢀ MPaꢀ atꢀ
haveꢀ theꢀ abilityꢀtoꢀincreaseꢀtheꢀsolubilityꢀofꢀ CO
2
.ꢀ Zhangꢀ etꢀ al.ꢀ
[42]ꢀ reportedꢀ thatꢀ theꢀ solubilityꢀ ofꢀ CO ꢀ increasedꢀ withꢀ theꢀ
2
1
lengthꢀofꢀtheꢀpolyethoxylꢀchain.ꢀHence,ꢀconsideringꢀtheꢀcost,ꢀweꢀ
Theꢀremainingꢀmixtureꢀwasꢀdistilledꢀunderꢀreducedꢀpressureꢀorꢀ
selectedꢀ5aꢀasꢀaꢀmodelꢀcatalystꢀforꢀfurtherꢀinvestigation.ꢀ
recrystallizedꢀwithꢀethanolꢀtoꢀobtainꢀtheꢀpureꢀcyclicꢀcarbonate.ꢀ
1
4
,5‐Tetramethylene‐1,3‐dioxolan‐2‐one.ꢀ Hꢀ NMRꢀ (500ꢀ M,ꢀ
3.2.ꢀ ꢀ Effectꢀofꢀreactionꢀtemperatureꢀonꢀtheꢀcouplingꢀreactionꢀ
CDCl
3
):ꢀδꢀ=ꢀ1.38–1.43ꢀ(m,ꢀ2H),ꢀ1.56–1.61ꢀ(m,ꢀ2H),ꢀ1.86–1.89ꢀ(m,ꢀ
1
4H),ꢀ 4.66–4.68ꢀ (m,ꢀ 2H);ꢀ Cꢀ NMRꢀ (125ꢀ M,ꢀ CDCl
3
):ꢀ δꢀ =ꢀ 19.39,ꢀ
Theꢀeffectꢀofꢀreactionꢀtemperatureꢀonꢀtheꢀcouplingꢀreactionꢀ
26.99,ꢀ76.02,ꢀ155.84.ꢀ
ofꢀ ECHꢀandꢀ CO ꢀisꢀ shownꢀinꢀFig.ꢀ1.ꢀTheꢀcatalyticꢀactivityꢀwasꢀ
2
sensitiveꢀtoꢀtemperature.ꢀTheꢀyieldꢀincreasedꢀsharplyꢀwhenꢀtheꢀ
temperatureꢀincreasedꢀfromꢀ60ꢀ°Cꢀtoꢀ120ꢀ°C.ꢀFurtherꢀtempera‐
tureꢀincreaseꢀhadꢀnoꢀsignificantꢀeffectꢀonꢀtheꢀconversionꢀwithꢀaꢀ
slightꢀ decreaseꢀ ofꢀ theꢀ yieldꢀ becauseꢀ ofꢀ sideꢀ reactionsꢀ [43].ꢀ
Therefore,ꢀtheꢀoptimumꢀreactionꢀtemperatureꢀisꢀ120ꢀ°C.ꢀ
3
.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
3.1.ꢀ ꢀ Hammettꢀacidityꢀfunction‐activityꢀrelationshipꢀ
0
TheꢀH ꢀfunctionꢀexpressesꢀtheꢀacidityꢀstrengthꢀofꢀanꢀacidꢀinꢀ
0
anꢀorganicꢀsolvent.ꢀTheꢀH ꢀofꢀtheꢀBAILsꢀisꢀlistedꢀinꢀTableꢀ1.ꢀUn‐
3.3.ꢀ ꢀ Effectꢀofꢀcatalystꢀamountꢀonꢀtheꢀcouplingꢀreactionꢀ
fortunatelyꢀ twoꢀ ionicꢀ liquidsꢀ showedꢀ noꢀ protonation,ꢀ butꢀ theꢀ
otherꢀresultsꢀeffectivelyꢀdistinguishedꢀtheꢀacidityꢀofꢀtheꢀvariousꢀ
ionicꢀliquids.ꢀTheꢀBrönstedꢀacidityꢀofꢀtheꢀBAILsꢀwithꢀdifferentꢀ
cationsꢀwasꢀdeterminedꢀ(entriesꢀ2–5,ꢀ7,ꢀandꢀ8).ꢀTheꢀacidityꢀofꢀ
theꢀBAILsꢀfollowedꢀtheꢀorderꢀ6ꢀ>ꢀ7ꢀ>ꢀ5aꢀ>ꢀ4ꢀ>ꢀ2,ꢀwhichꢀclearlyꢀ
indicatedꢀthatꢀtheꢀlengthꢀofꢀtheꢀcarbonꢀchainꢀinꢀtheꢀcationꢀin‐
fluencedꢀtheꢀacidityꢀofꢀtheꢀBAILs.ꢀAꢀlongerꢀcarbonꢀchainꢀinꢀtheꢀ
catalystꢀgaveꢀaꢀstrongerꢀacidity,ꢀwhichꢀwasꢀinꢀagreementꢀwithꢀ
ourꢀpreviousꢀreportedꢀworkꢀ(entriesꢀ2–5ꢀandꢀ8)ꢀ[38–40].ꢀItꢀwasꢀ
postulatedꢀthatꢀanꢀincreaseꢀinꢀtheꢀbulkinessꢀofꢀtheꢀalkylꢀchainꢀ
resultsꢀ inꢀ aꢀ decreaseꢀ inꢀ theꢀ electrostaticꢀ interactionꢀ betweenꢀ
theꢀcationꢀandꢀanion,ꢀconsequently,ꢀtheꢀacidityꢀincreasedꢀ[36].ꢀ
Also,ꢀ theꢀ acidityꢀ orderꢀ wasꢀ correlatedꢀ withꢀ theꢀ orderꢀ ofꢀ theꢀ
Theꢀ catalystꢀ amountꢀ wasꢀ alsoꢀ ofꢀ greatꢀ importanceꢀ forꢀ theꢀ
couplingꢀreaction.ꢀTheꢀeffectꢀofꢀtheꢀmolarꢀratioꢀofꢀtheꢀcatalystꢀ
onꢀtheꢀreactionꢀillustratedꢀthatꢀthereꢀ wereꢀnotꢀenoughꢀactiveꢀ
sitesꢀforꢀtheꢀreactionꢀwhenꢀtheꢀcatalystꢀamountꢀwasꢀlowꢀ(Fig.ꢀ
2).ꢀTheꢀyieldꢀincreasedꢀwithꢀtheꢀcatalystꢀamountꢀfromꢀ0.2ꢀmol%ꢀ
toꢀ0.8ꢀmol%,ꢀandꢀtheꢀyieldꢀremainedꢀconstantꢀwhenꢀtheꢀmolarꢀ
ratioꢀwasꢀaboveꢀ1.0ꢀmol%.ꢀOnꢀfurtherꢀincreaseꢀinꢀtheꢀamountꢀofꢀ
catalyst,ꢀ theꢀ yieldꢀ decreasedꢀ slightly,ꢀ therefore,ꢀ 1ꢀ mol%ꢀ wasꢀ
selectedꢀasꢀtheꢀbestꢀcatalystꢀamount.ꢀ
100
80
Tableꢀ1ꢀ ꢀ
H ꢀofꢀtheꢀBAILsꢀandꢀtheirꢀactivityꢀforꢀtheꢀcouplingꢀofꢀepichlorohydrinꢀ
0
withꢀCO
2
.ꢀ
60
Entryꢀ
BAILsꢀ
COOH)MIM]Brꢀ(1)ꢀ
COOH)TEA]Brꢀ(2)ꢀ
COOH)DMBA]Brꢀ(3)ꢀ
COOH)DMOA]Brꢀ(4)ꢀ
COOH)DMDA]Brꢀ(5a)ꢀ
COOH)DMDA]Clꢀ(5b)ꢀ
[DDPA]Brꢀ(6)ꢀ
H
Npꢀ
4.39ꢀ
Npꢀ
4.26ꢀ
4.03ꢀ
4.70ꢀ
2.51ꢀ
3.65ꢀ
0
ꢀ
Yieldꢀ(%)ꢀ
20.5ꢀ
38.1ꢀ
37.4ꢀ
45.4ꢀ
48.4ꢀ
42.5ꢀ
16.8ꢀ
49.8ꢀ
1
ꢀ
[(CH
[(CH
[(CH
[(CH
[(CH
2
40
2
ꢀ
2
3
ꢀ
2
4
ꢀ
2
20
0
5
ꢀ
2
ꢀ
a
6
7
8
ꢀ
[(CH
2
ꢀaꢀ
50
60 70 80 90 100 110 120 130 140
ꢀ
[(CH
2
COOH)DMHA]Brꢀ(7)ꢀ
o
T/ C
ConditionsꢀforꢀUV‐Visꢀspectrumꢀmeasurement:ꢀsolventꢀethanol,ꢀindica‐
torꢀdimethylꢀyellowꢀ(pK ꢀ=ꢀ3.3,ꢀ54ꢀμmol/L),ꢀBAILsꢀ30ꢀmmol/L,ꢀ25ꢀ°C.ꢀ
ꢀ
a
Fig.ꢀ1.ꢀEffectꢀofꢀreactionꢀtemperatureꢀonꢀtheꢀcouplingꢀreactionꢀinꢀtheꢀ
presenceꢀofꢀ5a.ꢀReactionꢀconditions:ꢀECHꢀ0.1ꢀmol,ꢀ5aꢀ1ꢀmol%,ꢀpꢀ=ꢀ0.9ꢀ
MPa,ꢀtꢀ=ꢀ0.5ꢀh.ꢀ
Reactionꢀconditions:ꢀepichlorohydrinꢀ(ECH)ꢀ0.1ꢀmol,ꢀcatalystꢀ1ꢀmol%,ꢀT
a
=
ꢀ100ꢀ°C,ꢀpꢀ=ꢀ0.9ꢀMPa,ꢀtꢀ=ꢀ0.5ꢀh.ꢀ ꢀ120ꢀ°C.ꢀNp:ꢀNoꢀprotonation.ꢀ

ꢀ
TaoꢀChangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ408–413ꢀ
Tableꢀ2ꢀ ꢀ
411ꢀ
100
Synthesisꢀofꢀotherꢀcyclicꢀcarbonatesꢀcatalyzedꢀbyꢀ5a.
ꢀ
9
8
7
6
5
4
3
2
0
0
0
0
0
0
0
0
Entryꢀ
Substrateꢀ
Productꢀ
tꢀ(h)ꢀ Yieldꢀ(%)
TOFꢀ
O
O
1
ꢀ
O
O
ꢀ 1.5ꢀ
ꢀ 0.5ꢀ
ꢀ 1.5ꢀ
ꢀ 2.5ꢀ
90.2ꢀ
96.7ꢀ
92.1ꢀ
89.6ꢀ
ꢀ 60.1ꢀ
193.4ꢀ
ꢀ 61.4ꢀ
ꢀ 35.8ꢀ
ꢀ
Oꢀ
O
2ꢀ
O
O
Cl
ꢀ
Cl
ꢀ
O
O
3ꢀ
O
O
ꢀ
ꢀ
O
O
4ꢀ
O
O
0.2
0.4
Catalyst amount (mol%)
Fig.ꢀ2.ꢀEffectꢀofꢀcatalystꢀamountꢀonꢀtheꢀcouplingꢀreactionꢀwithꢀcatalyst
0.6
0.8
1.0
1.2
Ph
ꢀ
Ph
Oꢀ
O
5
ꢀ
O
O
2ꢀ
90.6ꢀ
81.2ꢀ
ꢀ 40.3ꢀ
ꢀ ꢀ 5.4ꢀ
PhO
ꢀ
5
a.ꢀReactionꢀconditions:ꢀECHꢀ0.1ꢀmol,ꢀpꢀ=ꢀ0.9ꢀMPa,ꢀtꢀ=ꢀ0.5ꢀh.ꢀ
PhO
ꢀ
ꢀ
O
6ꢀ
O
O
15ꢀ
O
3.4.ꢀ ꢀ Reusabilityꢀofꢀ5aꢀforꢀtheꢀcouplingꢀreactionꢀ
Reactionꢀconditions:ꢀepoxidesꢀ0.1ꢀmol,ꢀcatalystꢀ5aꢀ1ꢀmol%,ꢀTꢀ=ꢀ120ꢀ°C,ꢀp
=ꢀ0.9ꢀMPa.ꢀ
Itꢀisꢀwellꢀknownꢀthatꢀtheꢀstabilityꢀandꢀreusabilityꢀofꢀaꢀcata‐
lystꢀsystemꢀareꢀtwoꢀkeyꢀfactorsꢀthatꢀidentifyꢀwhetherꢀitꢀcanꢀbeꢀ
appliedꢀinꢀindustry.ꢀToꢀtestꢀtheseꢀcharacteristicsꢀforꢀtheꢀcatalystꢀ
system,ꢀtheꢀcouplingꢀreactionꢀwasꢀcarriedꢀoutꢀunderꢀtheꢀopti‐
mumꢀ conditionsꢀ withꢀ theꢀ bestꢀ catalystꢀ 5a.ꢀ Afterꢀ theꢀ reaction,ꢀ
theꢀcatalystꢀwasꢀseparatedꢀfromꢀtheꢀvolatileꢀorganicꢀproductsꢀ
andꢀ startingꢀ materialsꢀ byꢀ distillationꢀ andꢀ reusedꢀ forꢀ theꢀ nextꢀ
cycle.ꢀAsꢀshownꢀinꢀFig.ꢀ3,ꢀafterꢀfiveꢀsuccessiveꢀrecycles,ꢀnoꢀsig‐
nificantꢀdropꢀinꢀtheꢀyieldꢀwasꢀdetected.ꢀ
inꢀparticular,ꢀtheꢀreactionꢀofꢀECHꢀandꢀCO ꢀwasꢀcompletedꢀwith‐
2
inꢀ30ꢀminꢀ(entryꢀ2).ꢀAromaticꢀepoxides,ꢀdueꢀtoꢀhindranceꢀfromꢀ
theꢀphenylꢀgroup,ꢀneedꢀaꢀlongerꢀreactionꢀtimeꢀtoꢀreachꢀaꢀgoodꢀ
conversionꢀ(entryꢀ4).ꢀAꢀmoreꢀhinderedꢀepoxideꢀneedsꢀaꢀlongerꢀ
reactionꢀtimeꢀ(entryꢀ6).ꢀItꢀcanꢀbeꢀseenꢀthatꢀtheꢀstericꢀeffectꢀisꢀ
veryꢀimportantꢀinꢀthisꢀcouplingꢀreaction.ꢀ
3.6.ꢀ ꢀ MechanismꢀforꢀtheꢀBAIL‐catalyzedꢀcouplingꢀreactionꢀ
3
.5.ꢀ ꢀ CyclicꢀcarbonateꢀsynthesisꢀfromꢀvariousꢀepoxidesꢀandꢀCO
2
ꢀ
Aꢀ mechanismꢀ forꢀ theꢀ BAIL‐catalyzedꢀ couplingꢀ ofꢀ epoxidesꢀ
catalyzedꢀbyꢀ5aꢀ
withꢀCO ꢀinꢀaccordanceꢀwithꢀpreviousꢀreportsꢀ[29–37]ꢀisꢀpro‐
2
posedꢀ inꢀ Schemeꢀ 2.ꢀ Theꢀ Brönstedꢀ acidꢀ centerꢀ ofꢀ theꢀ catalystꢀ
activatesꢀtheꢀepoxideꢀthroughꢀaꢀhydrogenꢀbondingꢀinteraction.ꢀ
TheꢀLewisꢀ basicꢀcenterꢀ (bromideꢀ anion)ꢀ attacksꢀtheꢀ activatedꢀ
carbonꢀofꢀtheꢀepoxideꢀleadingꢀtoꢀringꢀopeningꢀtoꢀgenerateꢀtheꢀ
alkoxideꢀ intermediate.ꢀ Finally,ꢀ theꢀ alkoxideꢀ intermediateꢀ un‐
Toꢀ furtherꢀ extendꢀ theꢀ scopeꢀ ofꢀ theꢀ reaction,ꢀ severalꢀ otherꢀ
epoxidesꢀwereꢀutilizedꢀasꢀtheꢀsubstrateꢀinꢀtheꢀcouplingꢀreactionꢀ
inꢀtheꢀpresenceꢀofꢀtheꢀbestꢀcatalystꢀ5a.ꢀTheꢀresultsꢀareꢀsumma‐
rizedꢀinꢀTableꢀ2.ꢀTheꢀcyclicꢀcarbonatesꢀwereꢀsynthesizedꢀwithꢀ
yieldsꢀfromꢀgoodꢀtoꢀexcellentꢀ(entriesꢀ1–6).ꢀAliphaticꢀepoxidesꢀ
wereꢀpreferredꢀsubstratesꢀforꢀtheꢀreactionꢀ(entriesꢀ1–3ꢀandꢀ5),ꢀ
2
dergoesꢀ theꢀ insertionꢀ ofꢀ CO ꢀ andꢀ subsequentꢀ ringꢀ closureꢀ toꢀ
O
O
R
100
O
A
N
COOH
Br-
O
R
80
60
40
20
0
BAILs
O
N
O
H
R
O
H O
N
O
O
O
Br-
A
O
A
Br
O
R
O
H
N
A
CO2
O
R
1
2
3
4
5
Catalytic run
Br
Fig.ꢀ 3.ꢀ Reusabilityꢀ ofꢀ catalystꢀ 5aꢀ forꢀ theꢀ couplingꢀ reaction.ꢀ Reactionꢀ
conditions:ꢀECHꢀ0.1ꢀmol,ꢀcatalystꢀ5aꢀ1ꢀmol%,ꢀpꢀ=ꢀ0.9ꢀMPa,ꢀtꢀ=ꢀ0.5ꢀh.ꢀ
Schemeꢀ2.ꢀProposedꢀmechanismꢀforꢀtheꢀBAIL‐catalyzedꢀcouplingꢀreac‐
tion.ꢀ

412ꢀ
TaoꢀChangꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ36ꢀ(2015)ꢀ408–413ꢀ
formꢀ theꢀ cyclicꢀ carbonateꢀ alongꢀ withꢀ theꢀ regenerationꢀ ofꢀ theꢀ
catalyst.ꢀ ꢀ
[16] LiꢀCꢀY,ꢀWuꢀCꢀR,ꢀLiuꢀYꢀC,ꢀKoꢀBꢀT.ꢀChemꢀCommun,ꢀ2012,ꢀ48:ꢀ9628ꢀ ꢀ
[17] RoeserꢀJ,ꢀKailasamꢀK,ꢀThomasꢀA.ꢀChemSusChem,ꢀ2012,ꢀ5:ꢀ1793ꢀ ꢀ
18] DaiꢀWꢀL,ꢀJinꢀB,ꢀLuoꢀSꢀL,ꢀLuoꢀXꢀB,ꢀTuꢀXꢀM,ꢀAuꢀCꢀT.ꢀCatalꢀToday,ꢀ2014,ꢀ
[
2
33:ꢀ92ꢀ
4.ꢀ ꢀ Conclusionsꢀ
[
19] ChenꢀJꢀX,ꢀJinꢀB,ꢀDaiꢀWꢀL,ꢀDengꢀSꢀL,ꢀCaoꢀLꢀR,ꢀCaoꢀZꢀJ,ꢀLuoꢀSꢀL,ꢀLuoꢀXꢀB,ꢀ
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LongꢀchainꢀBAILsꢀareꢀefficientꢀcatalystsꢀforꢀtheꢀcouplingꢀofꢀ
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Tetrahedron,ꢀ2012,ꢀ68:ꢀ3835ꢀ ꢀ
epoxidesꢀ andꢀ CO .ꢀ Theyꢀ areꢀ easyꢀ toꢀ synthesizeꢀ andꢀ areꢀ ther‐
2
[
mallyꢀstableꢀandꢀenvironmentallyꢀbenign.ꢀTheꢀrelationshipꢀbe‐
tweenꢀtheꢀacidityꢀandꢀcatalyticꢀactivityꢀofꢀtheꢀcatalystꢀwasꢀin‐
[
22] HeꢀQ,ꢀO’BrienꢀJꢀW,ꢀKitselmanꢀKꢀA,ꢀTompkinsꢀLꢀE,ꢀCurtisꢀGꢀCꢀT,ꢀKer‐
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