Synthesis of hexahydroquinolines using the new ionic liquid sulfonic acid functionalized pyridinium chloride as a catalyst

Article abstract of DOI:10.1016/S1872-2067(12)60678-0

Sulfonic acid functionalized pyridinium chloride [pyridine-SO ₃H]Cl has been synthesized as a novel Broensted acidic ionic liquid and characterized on the basis of its FT-IR, ¹H and ¹³C NMR, MS, thermogravimetry, and derivative thermogravimetry data. The material has also been used as a highly efficient, homogeneous, and reusable catalyst for the preparation of hexahydroquinolines according to the one-pot multi-component condensation of arylaldehydes, dimedone (5,5- dimethylcyclohexane-1,3-dione), β-ketoesters, and ammonium acetate under solvent-free conditions.

Full text of DOI:10.1016/S1872-2067(12)60678-0

ChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
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
Synthesisꢀofꢀhexahydroquinolinesꢀusingꢀtheꢀnewꢀionicꢀliquidꢀsulfonicꢀ
acidꢀfunctionalizedꢀpyridiniumꢀchlorideꢀasꢀaꢀcatalystꢀ
ꢀ
a,
ꢀa,#
ꢀb,‡
ꢀa
ArdeshirꢀKhazaei *,ꢀMohammadꢀAliꢀZolfigol ,ꢀAhmadꢀRezaꢀMoosavi‐Zare ,ꢀJavadꢀAfsar ,ꢀ ꢀ
ꢀc
ꢀa
ꢀd
AbdolkarimꢀZare ,ꢀVahidꢀKhakyzadeh ,ꢀMohammadꢀHassanꢀBeyzavi
ꢀ
aꢀFacultyꢀofꢀChemistry,ꢀBu‐AliꢀSinaꢀUniversity,ꢀHamedan,ꢀ6517838683,ꢀIranꢀ
bꢀDepartmentꢀofꢀChemistry,ꢀUniversityꢀofꢀSayyedꢀJamaleddinꢀAsadabadi,ꢀAsadabad,ꢀ6541835583,ꢀIranꢀ
cꢀDepartmentꢀofꢀChemistry,ꢀPayameꢀNoorꢀUniversity,ꢀPOꢀBOXꢀ19395‐4697ꢀTehran,ꢀIranꢀ
dꢀInstitutꢀfürꢀChemieꢀundꢀBiochemie,ꢀFreieꢀUniversitätꢀBerlin,ꢀTakustr.ꢀ3,ꢀ14195ꢀBerlin,ꢀGermanyꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Sulfonicꢀacidꢀfunctionalizedꢀpyridiniumꢀchlorideꢀ[pyridine‐SO H]Clꢀhasꢀbeenꢀsynthesizedꢀasꢀaꢀnovelꢀ
BrönstedꢀacidicꢀionicꢀliquidꢀandꢀcharacterizedꢀonꢀtheꢀbasisꢀofꢀitsꢀFT‐IR,ꢀ Hꢀandꢀ CꢀNMR,ꢀMS,ꢀther‐
mogravimetry,ꢀandꢀderivativeꢀthermogravimetryꢀdata.ꢀTheꢀmaterialꢀhasꢀalsoꢀbeenꢀusedꢀasꢀaꢀhighlyꢀ
efficient,ꢀhomogeneous,ꢀandꢀreusableꢀcatalystꢀforꢀtheꢀpreparationꢀofꢀhexahydroquinolinesꢀaccordingꢀ
Articleꢀhistory:ꢀ
3
1
13
Receivedꢀ31ꢀMayꢀ2013ꢀ
Acceptedꢀ14ꢀAugustꢀ2013ꢀ
Publishedꢀ20ꢀOctoberꢀ2013ꢀ
toꢀtheꢀone‐potꢀmulti‐componentꢀcondensationꢀofꢀarylaldehydes,ꢀdimedoneꢀ(5,5‐
ꢀ
dimethylcyclohex‐
ane‐1,3‐dione),ꢀβ‐ketoesters,ꢀandꢀammoniumꢀacetateꢀunderꢀsolvent‐freeꢀconditions.ꢀ
Keywords:ꢀ
Brönstedꢀacidicꢀionicꢀliquidꢀ
Sulfonicꢀacidꢀfunctionalizedꢀpyridinium
©ꢀ2013,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
3
chlorideꢀ[Pyridine‐SO H]Clꢀ
Hexahydroquinolineꢀ
Solvent‐freeꢀsynthesis
1
.ꢀ ꢀ Introductionꢀ
ronmentallyꢀ friendlyꢀ acidꢀ catalystsꢀ forꢀ organicꢀ synthesisꢀ be‐
causeꢀ theyꢀ effectivelyꢀ combineꢀ theꢀ advantagesꢀ ofꢀ liquidꢀ andꢀ
solidꢀ acidsꢀ andꢀ provideꢀ highꢀ levelsꢀ ofꢀ operationalꢀ simplicity,ꢀ
efficacy,ꢀandꢀselectivityꢀcoupledꢀwithꢀaꢀlowꢀenvironmentalꢀim‐
pactꢀ[11–18].ꢀ
Multi‐componentꢀreactionsꢀplayꢀanꢀimportantꢀroleꢀinꢀcom‐
binatorialꢀ chemistryꢀ becauseꢀ theyꢀ allowꢀ forꢀ complexꢀ targetꢀ
compoundsꢀ toꢀ beꢀ synthesizedꢀ inꢀ aꢀ singleꢀ stepꢀ fromꢀ threeꢀ orꢀ
moreꢀ reactantsꢀ withꢀ greaterꢀ simplicity,ꢀ efficiency,ꢀ andꢀ atomꢀ
economyꢀ thanꢀ theꢀ correspondingꢀ conventionalꢀ chemicalꢀ ap‐
proachesꢀ[5,19–21].ꢀ
Ionicꢀliquidsꢀ(ILs)ꢀhaveꢀattractedꢀconsiderableꢀinterestꢀfromꢀ
chemistsꢀduringꢀtheꢀcourseꢀofꢀtheꢀlastꢀtwoꢀdecadesꢀbecauseꢀofꢀ
theirꢀ uniqueꢀ properties,ꢀ includingꢀ theirꢀ non‐flammability,ꢀ
non‐volatility,ꢀwideꢀliquid‐stateꢀtemperatureꢀrange,ꢀhighꢀther‐
malꢀandꢀchemicalꢀstability,ꢀlargeꢀelectrochemicalꢀwindow,ꢀandꢀ
favorableꢀ solvationꢀ behaviorsꢀ [1,2].ꢀ Theseꢀ compoundsꢀ haveꢀ
beenꢀ appliedꢀ extensivelyꢀ toꢀ aꢀ numberꢀ ofꢀ differentꢀ areas,ꢀ in‐
cludingꢀspectroscopy,ꢀextraction,ꢀseparation,ꢀandꢀelectrochem‐
istryꢀ processesꢀ [1,3]ꢀ andꢀ areꢀ usedꢀ asꢀ solvents,ꢀ catalysts,ꢀ andꢀ
reagentsꢀinꢀaꢀvarietyꢀofꢀorganicꢀtransformationsꢀ[1,2,4–10].ꢀOfꢀ
theꢀmanyꢀdifferentꢀkindsꢀofꢀILsꢀavailable,ꢀtheꢀBrönstedꢀacidicꢀ
ILsꢀ offerꢀ theꢀ greatestꢀ potentialꢀ forꢀ theꢀ developmentꢀ ofꢀ envi‐
Someꢀ pharmaceuticalꢀ agentsꢀ canꢀ beꢀ photolabile,ꢀ andꢀ theꢀ
photochemicalꢀdecompositionꢀofꢀsuchꢀmaterialsꢀfollowingꢀtheirꢀ
exposureꢀtoꢀlightꢀcouldꢀresultꢀinꢀtheꢀreductionꢀorꢀcompleteꢀlossꢀ
*
ꢀCorrespondingꢀauthor.ꢀTel:ꢀ+98‐8118282807;ꢀFax:ꢀ+98‐8118257407;ꢀE‐mail:ꢀKhazaei_1326@yahoo.comꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+98‐8118282807;ꢀFax:ꢀ+98‐8118257407;ꢀE‐mail:ꢀmzolfigol@yahoo.comꢀ
Correspondingꢀauthor.ꢀTel:ꢀ+98‐8123237450;ꢀFax:ꢀ+98‐8123237451;ꢀE‐mail:ꢀmoosavizare@yahoo.comꢀ ꢀ
#
ꢀ
‡ꢀ
DOI:ꢀ10.1016/S1872‐2067(12)60678‐0ꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ34,ꢀNo.ꢀ10,ꢀOctoberꢀ2013ꢀ ꢀ ꢀ

ꢀ
ArdeshirꢀKhazaeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944ꢀ
ofꢀtheirꢀdesiredꢀpharmacologicalꢀactivity.ꢀFurthermore,ꢀphoto‐
chemicalꢀ decompositionꢀ couldꢀ evenꢀ leadꢀ toꢀ changesꢀ inꢀ theirꢀ
propertiesꢀ thatꢀ couldꢀ turnꢀ themꢀ intoꢀ potentiallyꢀ toxicꢀ com‐
pounds.ꢀ Inꢀ someꢀ cases,ꢀ theꢀ productsꢀ resultingꢀ fromꢀ photo‐
chemicalꢀdecompositionꢀcouldꢀinduceꢀhypersensitivityꢀtoꢀlightꢀ
andꢀpotentiallyꢀgiveꢀriseꢀtoꢀphotoallergicꢀandꢀphototoxicꢀeffectsꢀ
theꢀ preparationꢀ ofꢀ hexahydroquinolinesꢀ inꢀ theꢀ one‐potꢀ mul‐
ti‐componentꢀ condensationꢀ ofꢀ dimedone,ꢀ arylaldehydes,ꢀ
β‐ketoesters,ꢀandꢀammoniumꢀacetateꢀunderꢀsolvent‐freeꢀcondi‐
tionsꢀ(Schemeꢀ2).ꢀ
2.ꢀ ꢀ Experimental
[
22,23].ꢀ Forꢀ example,ꢀ 1,4‐dihydropyridineꢀ (DHP)ꢀ derivativesꢀ
areꢀincludedꢀinꢀtheꢀlongꢀlistꢀofꢀphotosensitiveꢀpharmaceuticalsꢀ
24,25].ꢀ
Accordingꢀ toꢀ researchꢀ availableꢀ inꢀ theꢀ literature,ꢀ oneꢀ ap‐
Allꢀ ofꢀ theꢀ chemicalsꢀ usedꢀ inꢀ theꢀ currentꢀ studyꢀ wereꢀ pur‐
chasedꢀ fromꢀ Merckꢀ orꢀ Flukaꢀ Chemical.ꢀ Theꢀ knownꢀ productsꢀ
wereꢀ identifiedꢀ byꢀ comparisonꢀ ofꢀ theirꢀ meltingꢀ pointsꢀ andꢀ
spectralꢀdataꢀwithꢀthoseꢀreportedꢀinꢀtheꢀliterature.ꢀTheꢀchemi‐
calꢀreactionsꢀwereꢀmonitoredꢀbyꢀTLCꢀusingꢀsilicaꢀgelꢀSILꢀG/UVꢀ
254ꢀplates.ꢀ HꢀNMRꢀ(400ꢀorꢀ300ꢀMHz)ꢀandꢀ CꢀNMRꢀ(100ꢀorꢀ75ꢀ
MHz)ꢀanalysesꢀwereꢀrunꢀonꢀaꢀBrukerꢀAvanceꢀDPX‐250ꢀFT‐NMRꢀ
spectrometer.ꢀTheꢀchemicalꢀshiftsꢀ(δ)ꢀhaveꢀbeenꢀreportedꢀrela‐
tiveꢀtoꢀTMS,ꢀwhichꢀwasꢀusedꢀasꢀanꢀinternalꢀreference.ꢀMeltingꢀ
pointsꢀwereꢀrecordedꢀonꢀaꢀBüchiꢀB‐545ꢀapparatusꢀinꢀopenꢀca‐
pillaryꢀtubes.ꢀ ꢀ
[
proachꢀ forꢀ reducingꢀ theꢀ photosensitivityꢀ ofꢀ pharmaceuticalꢀ
agentsꢀisꢀtoꢀmodifyꢀtheirꢀstructureꢀandꢀtheirꢀcoreꢀscaffold.ꢀMod‐
ificationsꢀ toꢀ theꢀ DHPꢀ ring,ꢀ suchꢀ asꢀ theꢀ introductionꢀ ofꢀ heteroꢀ
atomsꢀ orꢀ differentꢀ substituents,ꢀ couldꢀ notꢀ onlyꢀ resultꢀ inꢀ de‐
creasedꢀ photosensitivityꢀ inꢀ theseꢀ compoundsꢀ butꢀ couldꢀ alsoꢀ
enrichꢀ theꢀ diversityꢀ ofꢀ DHP‐basedꢀ chemistryꢀ andꢀ provideꢀ
structure‐activityꢀ relationshipsꢀ thatꢀ wouldꢀ provideꢀ novelꢀ in‐
sightsꢀintoꢀtheꢀmolecularꢀinteractionsꢀofꢀtheseꢀcompoundsꢀwithꢀ
theirꢀtargetꢀ[26,27].ꢀItꢀisꢀalsoꢀrecognizedꢀthatꢀstructuralꢀmodifi‐
cationsꢀtoꢀtheꢀDHPꢀperipheryꢀcouldꢀhaveꢀaꢀsignificantꢀimpactꢀonꢀ
theirꢀpharmacologicalꢀactivityꢀ[28–30].ꢀOneꢀseriesꢀofꢀDHPꢀde‐
rivativesꢀwithꢀanꢀimprovedꢀstructuralꢀscaffold,ꢀtheꢀhexahydro‐
quinolineꢀderivativesꢀ(HHQs),ꢀcanꢀbeꢀsynthesizedꢀaccordingꢀtoꢀ
1
13
2.1.ꢀ ꢀ Generalꢀprocedureꢀforꢀtheꢀpreparationꢀofꢀtheꢀ ꢀ
[pyridine‐SO H]Clꢀionicꢀliquidꢀ
3
Aꢀsolutionꢀofꢀpyridineꢀ(0.36ꢀg,ꢀ5ꢀmmol)ꢀinꢀCH
wasꢀaddedꢀdrop‐wiseꢀtoꢀaꢀstirredꢀsolutionꢀofꢀchlorosulfonicꢀacidꢀ
(0.58ꢀg,ꢀ5ꢀmmol)ꢀinꢀdryꢀCH Cl ꢀ(40ꢀmL)ꢀatꢀ0ꢀ°Cꢀoverꢀaꢀperiodꢀofꢀ
10ꢀmin,ꢀandꢀtheꢀresultingꢀmixtureꢀwasꢀstirredꢀforꢀ20ꢀminꢀbeforeꢀ
beingꢀ allowedꢀtoꢀ standꢀforꢀ 5ꢀ min.ꢀTheꢀCH Cl ꢀ layerꢀwasꢀthenꢀ
decantedꢀandꢀtheꢀresultingꢀresidueꢀwasꢀtrituratedꢀwithꢀCH Cl
(3ꢀ×ꢀ10ꢀmL)ꢀbeforeꢀbeingꢀdriedꢀunderꢀvacuumꢀatꢀ90ꢀ°Cꢀtoꢀgiveꢀ
2 2
Cl ꢀ(40ꢀmL)ꢀ
aꢀHantzschꢀ synthesisꢀusingꢀarylꢀaldehydes,ꢀdimedoneꢀ(5,5‐
di‐
ꢀ
methylcyclohexane‐1,3‐dione),ꢀ β‐ketoesters,ꢀ andꢀ ammoniumꢀ
acetateꢀ inꢀ aꢀ one‐potꢀ multi‐componentꢀ condensationꢀ reactionꢀ
2
2
[31,32].ꢀQuinolinesꢀbearingꢀaꢀ1,4‐dihydropyridineꢀscaffoldꢀhaveꢀ
2
2
beenꢀidentifiedꢀasꢀpromisingꢀstructureꢀinꢀmedicinalꢀchemistryꢀ
becauseꢀ ofꢀ theirꢀ manyꢀ pharmacologicalꢀ properties,ꢀ includingꢀ
theirꢀ antibacterialꢀ antihypertensive,ꢀ anti‐inflammatory,ꢀ anti‐
malarial,ꢀantiasthmatic,ꢀandꢀtyrosineꢀkinaseꢀinhibitoryꢀactivityꢀ
2
2
ꢀ
3
[pyridine‐SO H]Clꢀasꢀaꢀviscousꢀcolorlessꢀoilꢀinꢀ95ꢀ%ꢀyieldꢀ(0.93ꢀ
g).ꢀ
[33–38].ꢀ Furthermore,ꢀ variousꢀ methodsꢀ andꢀ catalystsꢀ haveꢀ
3
Spectralꢀ dataꢀ ofꢀ [pyridine‐SO H]Clꢀ areꢀ asꢀ follows.ꢀ Viscousꢀ
beenꢀdevelopedꢀforꢀtheꢀpreparationꢀofꢀHHQsꢀ[39–47].ꢀ
colorlessꢀ oil;ꢀ IRꢀ (Nujol):ꢀ 750,ꢀ 866,ꢀ 1042,ꢀ 1174,ꢀ 1488,ꢀ
–1 1
Herein,ꢀweꢀreportꢀforꢀtheꢀfirstꢀtimeꢀtheꢀsynthesisꢀofꢀsulfonicꢀ
2650–3550ꢀcm ;ꢀ HꢀNMRꢀ(300ꢀMHz,ꢀDMSO‐d
7.45ꢀHz,ꢀ2H),ꢀ8.65ꢀ(t,ꢀJꢀ=ꢀ7.81ꢀHz,ꢀ1H),ꢀ8.94ꢀ(d,ꢀJꢀ=ꢀ5.76ꢀHz,ꢀ2H),ꢀ
13.67ꢀ (s,ꢀ 1H);ꢀ 13Cꢀ NMRꢀ (75ꢀ MHz,ꢀ DMSO‐d
):ꢀ δꢀ 127.9,ꢀ 142.4,ꢀ
6
):ꢀδꢀ8.11ꢀ(t,ꢀJꢀ=ꢀ
acidꢀfunctionalizedꢀpyridiniumꢀchlorideꢀ[Pyridine‐SO
H]Clꢀasꢀaꢀ
3
newꢀ Brönstedꢀ acidicꢀ ionicꢀ liquidꢀ fromꢀ inexpensiveꢀ andꢀ com‐
merciallyꢀ availableꢀ startingꢀ materialsꢀ (Schemeꢀ 1),ꢀ andꢀ itsꢀ fullꢀ
characterizationꢀ usingꢀ FT‐IR,ꢀ Hꢀ andꢀ 13CꢀNMR,ꢀthermalꢀgravi‐
metricꢀanalysisꢀ(TGA)ꢀandꢀderivativeꢀthermalꢀgravimetricꢀanal‐
ysisꢀ(DTGA).ꢀFurthermore,ꢀweꢀreportꢀtheꢀuseꢀofꢀthisꢀionicꢀliquidꢀ
asꢀaꢀhighlyꢀefficient,ꢀhomogeneous,ꢀandꢀrecyclableꢀcatalystꢀforꢀ
6
+
+
147.1;ꢀMS:ꢀm/zꢀ=ꢀ196ꢀ[M+H] ,ꢀ195ꢀ[M] .ꢀ
2.2.ꢀ ꢀ Generalꢀprocedureꢀforꢀtheꢀsynthesisꢀofꢀhexahydroquinolinesꢀ
[Pyridine‐SO H]Clꢀ(11.7ꢀmg,ꢀ0.06ꢀmmol,ꢀ3ꢀmol%)ꢀwasꢀaddedꢀ
1
3
toꢀ aꢀ mixtureꢀ ofꢀ dimedoneꢀ (0.28ꢀ g,ꢀ 2ꢀ mmol),ꢀ arylaldehydeꢀ (2ꢀ
mmol),ꢀβ‐ketoesterꢀ(2ꢀmmol),ꢀandꢀammoniumꢀacetateꢀ(0.185ꢀg,ꢀ
Sulfur trioxide
pyridine complex
2
.4ꢀmmol)ꢀinꢀaꢀtestꢀtube,ꢀandꢀtheꢀresultingꢀmixtureꢀwasꢀinitiallyꢀ
stirredꢀmagneticallyꢀbeforeꢀbeingꢀagitatedꢀwithꢀaꢀsmallꢀrodꢀatꢀ
0ꢀ °Cꢀ followingꢀ solidificationꢀ ofꢀ theꢀ reactionꢀ mixture.ꢀ Uponꢀ
Pyridine
+
5
N
-
-
N
SO3
Cl
CH Cl
Ar
H
2
2
O
O
Ar
O
+
ClSO3H(neat)
3
[pyridine-SO H]Cl
O
R = Me, Et
HCl
O
O
(
3 mol%)
OR
N
Solvent-free
N
H
SO H
3
O
RO
o
5
0 C
-
Schemeꢀ1.ꢀPreparationꢀofꢀsulfonicꢀacidꢀfunctionalizedꢀpyridiniumꢀchlo‐
rideꢀ [pyridine‐SO H]Cl.ꢀ Left:ꢀ Theꢀ reactionꢀ ofꢀ pyridineꢀ (1ꢀ equiv.)ꢀ with
chlorosulfonicꢀacidꢀ(1ꢀequiv.)ꢀinꢀdryꢀCH Cl ꢀatꢀ0ꢀ°C;ꢀRight:ꢀTheꢀreaction
ofꢀsulfurꢀtrioxideꢀpyridineꢀcomplexꢀwithꢀanꢀexcessꢀofꢀHClꢀgasꢀatꢀroomꢀ
temperature.ꢀ
1 19
NH4OAc
3
2
2
Schemeꢀ2.ꢀOne‐potꢀmulti‐componentꢀpreparationꢀofꢀhexahydroquino‐
linesꢀcatalyzedꢀbyꢀ[pyridine‐SO H]Cl.ꢀ
3

ꢀ
ArdeshirꢀKhazaeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944ꢀ
ꢀ
completionꢀofꢀtheꢀreaction,ꢀasꢀdeterminedꢀbyꢀTLC,ꢀtheꢀreactionꢀ
mixtureꢀ wasꢀ cooledꢀ toꢀ roomꢀ temperatureꢀ andꢀ dilutedꢀ withꢀ
ethylꢀacetateꢀ(20ꢀmL).ꢀTheꢀresultingꢀmixtureꢀwasꢀthenꢀstirredꢀatꢀ
refluxꢀforꢀ3ꢀminꢀandꢀtheꢀsolventꢀdecantedꢀ(theꢀproductꢀisꢀsolu‐
droquinoline‐3‐carboxylateꢀ(5).ꢀWhiteꢀsolid;ꢀisolatedꢀyieldꢀ92%ꢀ
(0.32ꢀg);ꢀmeltingꢀpoint:ꢀ259–262ꢀ°Cꢀ(Ref.ꢀ[33]:ꢀ260–261ꢀ°C);ꢀ Hꢀ
1
NMRꢀ(500ꢀMHz,ꢀCDCl ):ꢀδꢀ0.96ꢀ(s,ꢀ3H),ꢀ1.08ꢀ(s,ꢀ3H),ꢀ1.24ꢀ(t,ꢀJꢀ=ꢀ
3
7.1ꢀHz,ꢀ3H),ꢀ2.15–2.31ꢀ(m,ꢀ7H),ꢀ2.35ꢀ(s,ꢀ3H),ꢀ4.09ꢀ(q,ꢀJꢀ=ꢀ7.1ꢀHz,ꢀ
2H),ꢀ5.04ꢀ(s,ꢀ1H),ꢀ6.76ꢀ(s,ꢀ1H),ꢀ7.02ꢀ(d,ꢀJꢀ=ꢀ7.8ꢀHz,ꢀ2H),ꢀ7.21ꢀ(d,ꢀJꢀ=ꢀ
bleꢀinꢀhotꢀethylꢀacetate;ꢀhowever,ꢀ[pyridine‐SO H]Clꢀisꢀnotꢀsolu‐
3
13
bleꢀ inꢀ thisꢀ solvent).ꢀ Theꢀ remainingꢀ viscousꢀ residueꢀ (oil)ꢀ wasꢀ
washedꢀwithꢀhotꢀethylꢀacetateꢀ(10ꢀmL)ꢀtoꢀgiveꢀtheꢀpureꢀrecycledꢀ
catalyst.ꢀTheꢀdecantedꢀsolutionsꢀwereꢀthenꢀcombined,ꢀwashedꢀ
withꢀ waterꢀ (20ꢀ mL),ꢀ andꢀ dried.ꢀ Theꢀ solventꢀ wasꢀ thenꢀ evapo‐
ratedꢀtoꢀgiveꢀtheꢀcrudeꢀproduct,ꢀwhichꢀwasꢀpurifiedꢀbyꢀrecrys‐
tallizationꢀ fromꢀ ethanolꢀ (95%)ꢀ orꢀ columnꢀ chromatographyꢀ
usingꢀ n‐hexane/ethylꢀ acetateꢀ (4/1,ꢀ v/v)ꢀ asꢀ anꢀ eluent.ꢀ Inꢀ theꢀ
7.8ꢀHz,ꢀ2H);ꢀ CꢀNMRꢀ(125ꢀMHz,ꢀCDCl ):ꢀδꢀ14.7,ꢀ19.7,ꢀ21.5,ꢀ27.6,ꢀ
3
29.8,ꢀ 33.1,ꢀ 36.6,ꢀ 41.3,ꢀ 51.2,ꢀ 60.2,ꢀ 106.6,ꢀ 112.4,ꢀ 128.3,ꢀ 129.0,ꢀ
135.8,ꢀ143.9,ꢀ144.7,ꢀ149.3,ꢀ167.9,ꢀ196.1.ꢀ
Ethylꢀ 4‐(4‐hydroxyphenyl)‐2,7,7‐trimethyl‐5‐oxo‐
ꢀ
1,4,5,6,7,ꢀ
8‐
ꢀ
hexahydroquinoline‐3‐carboxylateꢀ (6).ꢀWhiteꢀsolid;ꢀisolatedꢀ
yieldꢀ 94%ꢀ (0.33ꢀ g);ꢀ meltingꢀ point:ꢀ 234–236ꢀ °Cꢀ (Ref.ꢀ [33]:ꢀ
1
232–234ꢀ°C);ꢀ HꢀNMRꢀ(300ꢀMHz,ꢀDMSO‐d
6
):ꢀδꢀ0.86ꢀ(s,ꢀ3H),ꢀ1.00ꢀ
currentꢀwork,ꢀ[Pyridine‐SO
timesꢀwithoutꢀsignificantꢀlossꢀofꢀitsꢀcatalyticꢀactivity.ꢀ
Ethylꢀ 2,7,7‐trimethyl‐5‐oxo‐4‐phenyl‐1,4,5,6,7,8‐
droquinoline‐
3
H]Clꢀwasꢀrecycledꢀandꢀreusedꢀfourꢀ
(s,ꢀ3H),ꢀ1.14ꢀ(t,ꢀJꢀ=ꢀ7.0ꢀHz,ꢀ3H),ꢀ1.96ꢀ(d,ꢀJꢀ=ꢀ16.0ꢀHz,ꢀ1H),ꢀ2.15ꢀ(d,ꢀJꢀ
=ꢀ16.1ꢀHz,ꢀ1H),ꢀ2.26ꢀ(s,ꢀ3H),ꢀ2.36–2.49ꢀ(m,ꢀ2H),ꢀ3.96ꢀ(q,ꢀJꢀ=ꢀ7.0ꢀ
Hz,ꢀ2H),ꢀ4.74ꢀ(s,ꢀ1H),ꢀ6.56ꢀ(d,ꢀJꢀ=ꢀ8.1ꢀHz,ꢀ2H),ꢀ6.93ꢀ(d,ꢀJꢀ=ꢀ8.1ꢀHz,ꢀ
ꢀ
hexahy‐
13
ꢀ
3‐carboxylateꢀ(1).ꢀWhiteꢀsolid;ꢀisolatedꢀyieldꢀ94%ꢀ
2H),ꢀ8.94ꢀ(s,ꢀ1H),ꢀ9.01ꢀ(s,ꢀ1H);ꢀ CꢀNMRꢀ(75ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ
6
1
(0.32ꢀg);ꢀmeltingꢀpoint:ꢀ206–208ꢀ°Cꢀ(Ref.ꢀ[30]:ꢀ203–205ꢀ°C);ꢀ Hꢀ
14.6,ꢀ18.7,ꢀ26.9,ꢀ29.6,ꢀ32.6,ꢀ35.3,ꢀ50.8,ꢀ59.4,ꢀ104.6,ꢀ110.8,ꢀ114.9,ꢀ
128.8,ꢀ138.9,ꢀ144.8,ꢀ149.6,ꢀ155.7,ꢀ167.5,ꢀ194.7.ꢀ
6
NMRꢀ(300ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ0.85ꢀ(s,ꢀ3H),ꢀ1.00ꢀ(s,ꢀ3H),ꢀ1.13ꢀ(t,ꢀJꢀ
=
2
=
ꢀ 7.0ꢀ Hz,ꢀ 3H),ꢀ 2.01–2.20ꢀ (m,ꢀ 2H),ꢀ 2.29ꢀ (s,ꢀ 3H),ꢀ 2.38–2.50ꢀ (m,ꢀ
Ethylꢀ 4‐(4‐bromophenyl)‐2,7,7‐trimethyl‐5‐oxo‐1,4,5,6,7,8‐ꢀ
hexahydroquinoline‐3‐carboxylateꢀ (7).ꢀ Whiteꢀ solid;ꢀ isolatedꢀ
yieldꢀ 91%ꢀ (0.38ꢀ g);ꢀ meltingꢀ point:ꢀ 252–254ꢀ °Cꢀ (Ref.ꢀ [30]:ꢀ
ꢀ
H),ꢀ3.97ꢀ(q,ꢀJꢀ=ꢀ7.0ꢀHz,ꢀ2H),ꢀ4.82ꢀ(s,ꢀ1H),ꢀ7.05ꢀ(m,ꢀ1H),ꢀ7.18ꢀ(t,ꢀJꢀ
13
ꢀ6.7ꢀHz,ꢀ2H),ꢀ7.21ꢀ(t,ꢀJꢀ=ꢀ6.5ꢀHz,ꢀ2H),ꢀ9.12ꢀ(s,ꢀ1H);ꢀ CꢀNMRꢀ(75ꢀ
):ꢀδꢀ14.5,ꢀ18.8,ꢀ26.8,ꢀ29.5,ꢀ32.6,ꢀ36.5,ꢀ50.6,ꢀ59.6,ꢀ
03.4,ꢀ 109.9,ꢀ 113.5,ꢀ 126.9,ꢀ 128.8,ꢀ 130.5,ꢀ 146.0,ꢀ 150.3,ꢀ 167.0,ꢀ
94.7.ꢀ
Ethylꢀ 2,7,7‐trimethyl‐4‐(4‐nitrophenyl)‐5‐oxo‐
1
MHz,ꢀDMSO‐d
1
1
6
255–257ꢀ°C);ꢀ HꢀNMRꢀ(300ꢀMHz,ꢀDMSO‐d
6
):ꢀδꢀ0.83ꢀ(s,ꢀ3H),ꢀ0.99ꢀ
(s,ꢀ3H),ꢀ1.10ꢀ(t,ꢀJꢀ=ꢀ6.9ꢀHz,ꢀ3H),ꢀ1.96ꢀ(d,ꢀJꢀ=ꢀ16.0ꢀHz,ꢀ1H),ꢀ2.16ꢀ(d,ꢀJꢀ
=ꢀ16.1ꢀHz,ꢀ1H),ꢀ2.29ꢀ(s,ꢀ3H),ꢀ2.38–2.49ꢀ(m,ꢀ2H),ꢀ3.97ꢀ(q,ꢀJꢀ=ꢀ7.0ꢀ
Hz,ꢀ2H),ꢀ4.84ꢀ(s,ꢀ1H),ꢀ7.11ꢀ(d,ꢀJꢀ=ꢀ7.2ꢀHz,ꢀ2H),ꢀ7.37ꢀ(d,ꢀJꢀ=ꢀ7.2ꢀHz,ꢀ
ꢀ
1,4,5,6,7,8‐
ꢀ
hexahydroquinoline‐3‐carboxylateꢀ (2).ꢀ Whiteꢀ solid;ꢀ isolatedꢀ
2H),ꢀ 9.09ꢀ (s,ꢀ 1H);ꢀ 13Cꢀ NMRꢀ (75ꢀ MHz,ꢀ DMSO‐d
):ꢀ δꢀ 14.6,ꢀ 18.8,ꢀ
6
yieldꢀ 95%ꢀ (0.37ꢀ g);ꢀ meltingꢀ point:ꢀ 245–248ꢀ °Cꢀ (Ref.ꢀ [34]:ꢀ
26.9,ꢀ 29.5,ꢀ 32.6,ꢀ 36.2,ꢀ 50.6,ꢀ 59.5,ꢀ 103.5,ꢀ 110.1,ꢀ 119.1,ꢀ 130.2,ꢀ
131.0,ꢀ145.8,ꢀ147.4,ꢀ150.0,ꢀ167.1,ꢀ194.7.ꢀ
1
3
242–244ꢀ°C);ꢀ HꢀNMRꢀ(500ꢀMHz,ꢀCDCl ):ꢀδꢀ0.92ꢀ(s,ꢀ3H),ꢀ1.10ꢀ(s,ꢀ
3H),ꢀ1.19ꢀ(t,ꢀJꢀ=ꢀ7.1ꢀHz,ꢀ3H),ꢀ2.16ꢀ(d,ꢀJꢀ=ꢀ16.4ꢀHz,ꢀ2H),ꢀ2.24–2.29ꢀ
Ethylꢀ 4‐(4‐chlorophenyl)‐2,7,7‐trimethyl‐5‐oxo‐
ꢀ
1,4,5,6,7,8‐
ꢀ
(
5
distortedꢀABꢀsystem,ꢀ2H),ꢀ2.41ꢀ(s,ꢀ3H),ꢀ4.07ꢀ(q,ꢀJꢀ=ꢀ7.1ꢀHz,ꢀ2H),ꢀ
.18ꢀ(s,ꢀ1H),ꢀ6.68ꢀ(s,ꢀ1H),ꢀ7.51ꢀ(d,ꢀJꢀ=ꢀ8.5ꢀHz,ꢀ2H),ꢀ8.09ꢀ(d,ꢀJꢀ=ꢀ8.5ꢀ
Hz,ꢀ 2H);ꢀ 13Cꢀ NMRꢀ (125ꢀ MHz,ꢀ CDCl
):ꢀ δꢀ 14.6,ꢀ 19.8,ꢀ 27.5,ꢀ 29.8,ꢀ
3.1,ꢀ 37.7,ꢀ 41.3,ꢀ 51.0,ꢀ 60.5,ꢀ 105.3,ꢀ 111.4,ꢀ 123.7,ꢀ 129.4,ꢀ 145.0,ꢀ
hexahydroquinoline‐3‐carboxylateꢀ (9).ꢀ Whiteꢀ solid;ꢀ isolatedꢀ
yieldꢀ 91%ꢀ (0.35ꢀ g);ꢀ meltingꢀ point:ꢀ 244–246ꢀ °Cꢀ (Ref.ꢀ [32]:ꢀ
–1
1
3
245–246ꢀ°C);ꢀIRꢀ(KBr):ꢀ3274,ꢀ1707,ꢀ1605,ꢀ1489,ꢀ1382ꢀcm ;ꢀ Hꢀ
NMRꢀ(400ꢀMHZ,ꢀDMSO‐d ):ꢀδꢀ0.82ꢀ(s,ꢀ3H),ꢀ0.99ꢀ(s,ꢀ3H),ꢀ1.11ꢀ(t,ꢀJꢀ
3
1
6
46.6,ꢀ149.6,ꢀ154.9,ꢀ167.3,ꢀ195.9.ꢀ
=ꢀ7.08Hz,ꢀ3H),ꢀ1.97ꢀ(d,ꢀJꢀ=ꢀ16.08,ꢀ3H),ꢀ2.16ꢀ(ꢀd,ꢀJꢀ=ꢀ16.12ꢀHz,1H),ꢀ
2.43–2.50ꢀ(distortedꢀABꢀsystem,ꢀ2H),ꢀ3.96ꢀ(d,ꢀJꢀ=ꢀ7.08ꢀHz,ꢀ2H),ꢀ
4.83ꢀ(s,ꢀ1H),ꢀ7.15ꢀ(d,ꢀJꢀ=ꢀ8.48,ꢀ2H),ꢀ7.24ꢀ(d,ꢀJꢀ=ꢀ8.44,ꢀ2H),ꢀ9.01ꢀ(s,ꢀ
1H).ꢀ
Ethylꢀ 2,7,7‐trimethyl‐4‐(3‐nitrophenyl)‐5‐oxo‐1,4,5,6,7,8‐
ꢀ
hexahydroquinoline‐3‐carboxylateꢀ (3).ꢀ Whiteꢀ solid;ꢀ isolatedꢀ
yieldꢀ 94%ꢀ (0.36ꢀ g);ꢀ meltingꢀ point:ꢀ 179–181ꢀ °Cꢀ (Ref.ꢀ [32]:ꢀ
1
1
1
1
2
77–178ꢀ °C);ꢀ IRꢀ (KBr):ꢀ 3285,ꢀ 2959,ꢀ 1705,ꢀ 1606,ꢀ 1487,ꢀ 1380,ꢀ
Ethylꢀ 4‐(2‐methoxyphenyl)‐2,7,7‐trimethyl‐5‐oxo‐
hexahydroquinoline‐3‐carboxylateꢀ(10).ꢀWhiteꢀsolid;ꢀisolatedꢀ
yieldꢀ 96%ꢀ (0.35ꢀ g);ꢀ meltingꢀ point:257–259ꢀ °Cꢀ (Ref.ꢀ [10]:ꢀ
256–257ꢀ °C);ꢀ IRꢀ (KBr):ꢀ 3285,ꢀ 2957,ꢀ 1689,ꢀ 1611,ꢀ 1488,ꢀ 1381,ꢀ
ꢀ
1,4,5,6,7,ꢀ
–1 1
6
212ꢀcm ;ꢀ HꢀNMRꢀ(400ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ(s,ꢀ3H),ꢀ1.00ꢀ(s,ꢀ3H),ꢀ
8‐
ꢀ
.10ꢀ(t,ꢀJꢀ=7.04ꢀHz,ꢀ3H),ꢀ1.98ꢀ(d,ꢀJꢀ=ꢀ16.12ꢀHz,ꢀ1H),ꢀ2.19ꢀ(d,ꢀJꢀ=ꢀ
6.12ꢀ Hz,ꢀ 1H),ꢀ 2.31ꢀ (s,ꢀ 3H),ꢀ 2.42–2.50ꢀ (distortedꢀ ABꢀ system,ꢀ
H),ꢀ3.99–3.94ꢀ(m,ꢀ2H),ꢀ4.95ꢀ(s,ꢀ1H),ꢀ7.52ꢀ(t,ꢀJꢀ=ꢀ8.0ꢀHz,ꢀ1H),ꢀ7.61ꢀ
–1 1
1216ꢀcm ;ꢀ HꢀNMRꢀ(400ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ0.83ꢀ(s,ꢀ3H),ꢀ0.99ꢀ(s,ꢀ
6
13
(
d,ꢀ7.68ꢀHz,ꢀ1H),ꢀ7.97ꢀ(t,ꢀJꢀ=ꢀ2.16ꢀHz,ꢀ2H),ꢀ9.25ꢀ(s,ꢀ1H);ꢀ CꢀNMRꢀ
400ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ13.99,ꢀ18.31,ꢀ26.30,ꢀ29.01,ꢀ32.16,ꢀ36.36,ꢀ
8.8,ꢀ 49.98,ꢀ 59.22,ꢀ 102.59,ꢀ 109.17,ꢀ 120.89,ꢀ 121.95,ꢀ 129.41,ꢀ
34.28,ꢀ146.11,ꢀ147.34,ꢀ149.69,ꢀ150.12,ꢀ166.36,ꢀ194.31.ꢀ ꢀ
Ethylꢀ 4‐(4‐methoxyphenyl)‐2,7,7‐trimethyl‐5‐oxo‐1,4,5,6,7,ꢀ
ꢀꢀhexahydroquinoline‐3‐carboxylateꢀ (4).ꢀWhiteꢀsolid;ꢀisolatedꢀ
3H),ꢀ1.10ꢀ(t,ꢀJꢀ=ꢀ7.08ꢀHz,ꢀ3H),ꢀ1.89ꢀ(d,ꢀJꢀ=ꢀ16.08ꢀHz,ꢀ1H),ꢀ2.11ꢀ(d,ꢀJꢀ
=ꢀ16.08ꢀHz,ꢀ1H),ꢀ2.18ꢀ(s,ꢀ3H),ꢀ2.40–2.50ꢀ(distortedꢀABꢀsystem,ꢀ
2H),ꢀ3.68ꢀ(s,ꢀ3H),ꢀ3.91ꢀ(q,ꢀJꢀ=ꢀ3.64ꢀHz,ꢀ2H),ꢀ5.04ꢀ(s,ꢀ1H),ꢀ6.75ꢀ(d,ꢀJꢀ
=ꢀ7.44ꢀHz,ꢀ1H),ꢀ6.82ꢀ(d,ꢀJꢀ=ꢀ8.04ꢀHz,ꢀ1H),ꢀ7.03ꢀ(d,ꢀJꢀ=ꢀ7.36ꢀHz,ꢀ1H),ꢀ
7.09ꢀ (q,ꢀ Jꢀ =ꢀ 1.44ꢀ Hz,ꢀ 1H),ꢀ 8.93ꢀ (s,ꢀ 1H);ꢀ 13Cꢀ NMRꢀ (400ꢀ MHz,ꢀ
(
3
1
6
ꢀ
8‐
DMSO‐d ):ꢀ δꢀ 14.05,ꢀ 18.00,ꢀ 26.15,ꢀ 29.28,ꢀ 31.95,ꢀ 32.77,ꢀ 50.36,ꢀ
6
yieldꢀ 95%ꢀ (0.35ꢀ g);ꢀ meltingꢀ point:ꢀ 256–258ꢀ °Cꢀ (Ref.ꢀ [33]:ꢀ
55.14,ꢀ 58.72,ꢀ 102.89,ꢀ 108.64,ꢀ 110.96,ꢀ 119.44,ꢀ 126.90,ꢀ 130.46,ꢀ
134.93,ꢀ144.08,ꢀ149.94,ꢀ157.10,ꢀ167.26,ꢀ193.79.ꢀ ꢀ
1
6
257–259ꢀ°C);ꢀ HꢀNMRꢀ(300ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ0.85ꢀ(s,ꢀ3H),ꢀ1.00ꢀ
(
=
3
s,ꢀ3H),ꢀ1.14ꢀ(t,ꢀJꢀ=ꢀ7.0ꢀHz,ꢀ3H),ꢀ1.96ꢀ(d,ꢀJꢀ=ꢀ16.0ꢀHz,ꢀ1H),ꢀ2.15ꢀ(d,ꢀJꢀ
ꢀ 16.1ꢀ Hz,ꢀ 1H),ꢀ 2.27ꢀ (s,ꢀ 3H),ꢀ 2.37–2.49ꢀ (m,ꢀ 2H),ꢀ 3.66ꢀ (s,ꢀ 3H),ꢀ
.97ꢀ(q,ꢀJꢀ=ꢀ7.0ꢀHz,ꢀ2H),ꢀ4.79ꢀ(s,ꢀ1H),ꢀ6.73ꢀ(d,ꢀJꢀ=ꢀ8.3ꢀHz,ꢀ2H),ꢀ7.05ꢀ
Ethylꢀ 4‐(2,4‐dichlorophenyl)‐2,7,7‐trimethyl‐5‐oxo‐
7,8‐hexahydroquinoline‐3‐carboxylateꢀ (11).ꢀ Whiteꢀ solid;ꢀ iso‐
latedꢀyieldꢀ94%ꢀ(0.38ꢀg);ꢀmeltingꢀpoint:ꢀ243–245ꢀ°C;ꢀIRꢀ(KBr):ꢀ
ꢀ
1,4,5,6,ꢀ
ꢀ
13
–1 1
(d,ꢀJꢀ=ꢀ8.3ꢀHz,ꢀ2H),ꢀ8.99ꢀ(s,ꢀ1H);ꢀ CꢀNMRꢀ(75ꢀMHz,ꢀDMSO‐d
6
):ꢀδꢀ
4.6,ꢀ18.7,ꢀ26.9,ꢀ29.6,ꢀ32.6,ꢀ35.4,ꢀ50.6,ꢀ55.3,ꢀ59.4,ꢀ104.4,ꢀ110.7,ꢀ
13.5,ꢀ128.8,ꢀ140.5,ꢀ145.1,ꢀ149.7,ꢀ157.7,ꢀ167.4,ꢀ194.7.ꢀ ꢀ
Ethylꢀ 2,7,7‐trimethyl‐5‐oxo‐4‐p‐tolyl‐1,4,5,6,7,8‐
3285,ꢀ1706,ꢀ1609,ꢀ1493,ꢀ1381,ꢀ1214ꢀcm ;ꢀ HꢀNMRꢀ(400ꢀMHz,ꢀ
DMSO‐d ):ꢀδꢀ0.83ꢀ(s,ꢀ3H),ꢀ0.92ꢀ(s,ꢀ3H),ꢀ1.07ꢀ(t,ꢀJꢀ=ꢀ7.08ꢀHz,ꢀ3H),ꢀ
1
1
6
1.91ꢀ(d,ꢀJꢀ=ꢀ16.04ꢀHz,ꢀ1H),ꢀ2.14ꢀ(d,ꢀJꢀ=ꢀ16.08ꢀHz,ꢀ1H),ꢀ2.22ꢀ(s,ꢀ3H),ꢀ
2.49–2.50ꢀ(distortedꢀABꢀsystem,ꢀ2H),ꢀ3.95–3.91ꢀ(m,ꢀ2H),ꢀ5.14ꢀ(s,ꢀ
ꢀ
hexahy‐

ꢀ
ArdeshirꢀKhazaeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944ꢀ
1
3
(KBr):ꢀ3284,ꢀ3215,ꢀ2961,ꢀ1702,ꢀ1612,ꢀ1493,ꢀ1379,ꢀ1218ꢀcm–1;ꢀ
1HꢀNMRꢀ(400ꢀMHz,ꢀDMSO‐d
):ꢀδꢀ0.97ꢀ(s,ꢀ12H),ꢀ1.06ꢀ(t,ꢀJꢀ=ꢀ6.96ꢀ
1
H),ꢀ7.31ꢀ(s,ꢀ2H),ꢀ7.34ꢀ(s,ꢀ1H),ꢀ9.12ꢀ(s,ꢀ1H);ꢀ CꢀNMRꢀ(400ꢀMHz,ꢀ
):ꢀ δꢀ 14.07,ꢀ 18.19,ꢀ 26.37,ꢀ 29.01,ꢀ 31.94,ꢀ 34.73,ꢀ 50.14,ꢀ
8.99,ꢀ 102.69,ꢀ 109.18,ꢀ 126.83,ꢀ 128.16,ꢀ 130.70,ꢀ 132.75,ꢀ
DMSO‐d
5
1
6
6
Hz,ꢀ6H),ꢀ2.09–2.13ꢀ(m,ꢀ2H),ꢀ2.26ꢀ(s,ꢀ6H)ꢀ2.45–2.50ꢀ(m,ꢀ2H),ꢀ3.96ꢀ
+
13
32.82,144.19,ꢀ145.44,ꢀ149.85,ꢀ196.3;ꢀMS:ꢀm/zꢀ=ꢀ373ꢀ[M] ;ꢀCHNꢀ
NO :ꢀCꢀ61.77,ꢀHꢀ5.68,ꢀNꢀ3.43;ꢀ
(q,ꢀJꢀ=ꢀ3.96ꢀHz,ꢀ4H),ꢀ4.79ꢀ(s,ꢀ2H),ꢀ6.92ꢀ(s,ꢀ4H),ꢀ9.01ꢀ(s,ꢀ2H);ꢀ Cꢀ
Analysis:ꢀAnal.ꢀCalcdꢀforꢀC21
FoundꢀCꢀ61.43,ꢀHꢀ5.96,ꢀNꢀ3.27.ꢀ
Ethylꢀ 2,7,7‐trimethyl‐5‐oxo‐4‐(naphthalen‐2‐yl)‐1,4,5,6,7,8‐
H23Cl
2
3
NMRꢀ(400ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ14.08,ꢀ18.28,ꢀ26.75,ꢀ27.91,ꢀ28.85,ꢀ
6
32.13,ꢀ 34.77,ꢀ 50.22,ꢀ 58.97,ꢀ 102.38,ꢀ 103.35,ꢀ 109.82,ꢀ 126.61,ꢀ
+
ꢀ
144.65,ꢀ 149.61,ꢀ 166.90;ꢀ MS:ꢀ m/zꢀ =ꢀ 600ꢀ [M] ;ꢀ CHNꢀ Analysis:ꢀ
hexahydroquinoline‐3‐carboxylateꢀ (12).ꢀ Whiteꢀ solid;ꢀ isolatedꢀ
Anal.ꢀ Calcdꢀ forꢀ C36
H
44
N
2
O :ꢀ Cꢀ 71.97,ꢀ Hꢀ 7.38,ꢀ Nꢀ 4.66;ꢀ Foundꢀ Cꢀ
6
yieldꢀ92%ꢀ(0.36ꢀg);ꢀmeltingꢀpoint:ꢀ235–237ꢀ°C;ꢀIRꢀ(KBr):ꢀ3253,ꢀ
71.68,ꢀHꢀ7.23,ꢀNꢀ4.71.ꢀ
–1 1
1
0
1
701,ꢀ1607,ꢀ1493,ꢀ1217ꢀcm ;ꢀ HꢀNMRꢀ(400ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ
.82ꢀ(s,ꢀ3ꢀH),ꢀ1.00ꢀ(s,ꢀ3H),ꢀ1.12ꢀ(t,ꢀJꢀ=ꢀ7.08ꢀHz,ꢀ3H),ꢀ1.95ꢀ(d,ꢀJꢀ=ꢀ
6.12ꢀHz,ꢀ1H),ꢀ2.18ꢀ(d,ꢀJꢀ=ꢀ16.16ꢀHz,ꢀ1H),ꢀ2.31ꢀ(s,ꢀ3H),ꢀ2.42–2.50ꢀ
6
3.ꢀ ꢀ Resultsꢀandꢀdiscussion
3.1.ꢀ ꢀ Characterizationꢀofꢀ[pyridine‐SO
Theꢀstructureꢀofꢀtheꢀsulfonicꢀacidꢀfunctionalizedꢀpyridiniumꢀ
chlorideꢀwasꢀcharacterizedꢀonꢀtheꢀbasisꢀofꢀitsꢀ Hꢀandꢀ CꢀNMR,ꢀ
IR,ꢀUV,ꢀandꢀMSꢀdata,ꢀwhichꢀwereꢀpresentedꢀinꢀtheꢀExperimentalꢀ
section.ꢀ
(
7
distortedꢀABꢀsystem,ꢀ2H),ꢀ3.95ꢀ(q,ꢀJꢀ=ꢀ7.12ꢀHz,ꢀ2H),ꢀ5.03ꢀ(s,ꢀ1H),ꢀ
.43–7.36ꢀ(m,ꢀ3H),ꢀ7.58ꢀ(s,ꢀ1H),ꢀ7.79–7.78ꢀ(m,ꢀ3H),ꢀ9.11ꢀ(s,ꢀ1H),;ꢀ
13Cꢀ NMRꢀ (400ꢀ MHz,ꢀ DMSO‐d
):ꢀ δꢀ 14.12,ꢀ 18.29,ꢀ 26.35,ꢀ 29.12,ꢀ
2.10,ꢀ 36.20,ꢀ 50.21,ꢀ 59.02,ꢀ 103.38,ꢀ 109.74,ꢀ 125.11,ꢀ 125.32,ꢀ
3
H]Cl
6
1
13
3
1
1
25.73,ꢀ126.68,ꢀ127.22,ꢀ127.28,ꢀ127.56,ꢀ131.60,ꢀ132.72,ꢀ144.99,ꢀ
+
45.14,ꢀ 149.64,ꢀ 166.81,ꢀ 194.30;ꢀ MS:ꢀ m/zꢀ =ꢀ 389ꢀ [M] ;ꢀ CHNꢀ
Analysis:ꢀ Anal.ꢀ Calcdꢀ forꢀ C25
FoundꢀCꢀ76.88,ꢀHꢀ6.91,ꢀNꢀ3.68.ꢀ
Ethylꢀ 4‐(3‐hydroxyphenyl)‐2,7,7‐trimethyl‐5‐oxo‐
hexahydroquinoline‐3‐carboxylateꢀ(13).ꢀWhiteꢀsolid;ꢀisolatedꢀ
yieldꢀ92%ꢀ(0.33ꢀg);ꢀmeltingꢀpoint:ꢀ211–213ꢀ°C;ꢀIRꢀ(KBr):ꢀ3408,ꢀ
H
27NO
3
:ꢀ Cꢀ 77.09,ꢀ Hꢀ 6.99,ꢀ Nꢀ 3.60;ꢀ
TheꢀIRꢀspectrumꢀofꢀtheꢀcatalystꢀcontainedꢀaꢀbroadꢀpeakꢀatꢀ
–1
2650–3550ꢀcm ,ꢀwhichꢀwasꢀattributedꢀtoꢀtheꢀO–Hꢀstretchingꢀofꢀ
theꢀSO Hꢀgroup.ꢀInꢀaddition,ꢀtheꢀtwoꢀpeaksꢀobservedꢀatꢀ1042ꢀ
andꢀ1174ꢀcm ꢀwereꢀassignedꢀtoꢀtheꢀvibrationalꢀmodesꢀofꢀtheꢀ
N–SO ꢀandꢀO–SO ꢀbondsꢀ(Fig.ꢀ1).ꢀ
Theꢀ Hꢀandꢀ CꢀNMRꢀspectraꢀofꢀtheꢀ[pyridine‐SO
ꢀ
1,4,5,6,7,ꢀ
3
–1
8
‐
ꢀ
2
2
–1
1
1
13
3
289,ꢀ 1675,ꢀ 1606,ꢀ 1485,ꢀ 1220ꢀ cm ;ꢀ Hꢀ NMRꢀ (400ꢀ MHz,ꢀ
DMSO‐d ):ꢀδꢀ0.86ꢀ(s,ꢀ3H),ꢀ1.00ꢀ(s,ꢀ3H).ꢀ1.13ꢀ(t,ꢀJꢀ=ꢀ7.04ꢀHz,ꢀ3H),ꢀ
.00ꢀ(s,ꢀ1H),ꢀ2.15ꢀ(d,ꢀJꢀ=ꢀ16.08ꢀHz,ꢀ1H),ꢀ2.26ꢀ(s,ꢀ3H),ꢀ2.38–2.50ꢀ
distortedꢀABꢀsystem,ꢀ2H),ꢀ3.97ꢀ(q,ꢀJꢀ=ꢀ7.08ꢀHz,ꢀ2H),ꢀ4.78ꢀ(s,ꢀ1H),ꢀ
3
H]Clꢀcata‐
1
6
lystꢀareꢀshownꢀinꢀFig.ꢀ2.ꢀTheꢀpeakꢀatꢀδꢀ=ꢀ13.67ꢀinꢀtheꢀ HꢀNMRꢀ
2
(
spectrumꢀ wasꢀ assignedꢀ toꢀ theꢀ acidicꢀ hydrogenꢀ ofꢀ theꢀ SO Hꢀ
3
group.ꢀToꢀconfirmꢀthisꢀassignmentꢀthroughꢀaꢀprocessꢀofꢀelimi‐
1
6
1
1
1
.46–6.43ꢀ(m,ꢀ1ꢀH),ꢀ6.57ꢀ(d,ꢀJꢀ=ꢀ7.24ꢀHz,ꢀ2H),ꢀ6.93ꢀ(t,ꢀJꢀ=ꢀ7.96ꢀHz,ꢀ
nation,ꢀ weꢀ alsoꢀ collectedꢀ theꢀ Hꢀ NMRꢀ spectraꢀ ofꢀ ClSO
3
Hꢀ andꢀ
13
H),ꢀ9.01ꢀ(s,ꢀ1H),ꢀ9.06ꢀ(s,ꢀ1H);ꢀ CꢀNMRꢀ(22.5ꢀMHz,ꢀDMSO‐d
6
):ꢀδꢀ
6
pyridiniumꢀchlorideꢀinꢀDMSO‐d ꢀ(theꢀacidicꢀhydrogensꢀofꢀpyri‐
4.8,ꢀ18.9,ꢀ27.4,ꢀ29.8,ꢀ32.8,ꢀ36.4,ꢀ40.4,ꢀ51.2,ꢀ59.7,ꢀ104.6,ꢀ110.8,ꢀ
13.4,ꢀ 115.4,ꢀ 119.0,ꢀ 129.3,ꢀ 145.4,ꢀ 150.2,ꢀ 157.7,ꢀ 167.8,ꢀ 195.0;ꢀ
diniumꢀ chlorideꢀ andꢀ pyridiniumꢀ chlorosulfonateꢀ gaveꢀ similarꢀ
1
chemicalꢀ shifts).ꢀ Allꢀ ofꢀ theꢀ samplesꢀ involvedꢀ inꢀ thisꢀ Hꢀ NMRꢀ
+
MS:ꢀm/zꢀ=ꢀ355ꢀ[M] ;ꢀCHNꢀAnalysis:ꢀAnal.ꢀCalcdꢀforꢀC21
4
H25NO :ꢀCꢀ
studyꢀ wereꢀ preparedꢀ atꢀ aꢀ concentrationꢀ ofꢀ 0.08ꢀ mol/L.ꢀ Theꢀ
peaksꢀ correspondingꢀ toꢀ theꢀ acidicꢀ hydrogensꢀ ofꢀ pyridiniumꢀ
7
0.96,ꢀHꢀ7.09,ꢀNꢀ3.94;ꢀFoundꢀCꢀ70.67,ꢀHꢀ7.18,ꢀNꢀ3.81.ꢀ
Methylꢀ 4‐(4‐methoxyphenyl)‐2,7,7‐trimethyl‐5‐oxo‐
,8‐hexahydroquinoline‐3‐carboxylateꢀ (17).ꢀ Whiteꢀ solid;ꢀ iso‐
ꢀ
1,4,5,6,ꢀ
chloride,ꢀ ClSO
3
H,ꢀ andꢀ [pyridine‐SO H]Clꢀ wereꢀ detectedꢀ atꢀ δꢀ =ꢀ
3
7
ꢀ
11.37,ꢀ13.45,ꢀandꢀ13.67,ꢀrespectively.ꢀTheꢀdifferencesꢀbetweenꢀ
latedꢀyieldꢀ91%ꢀ(0.32ꢀg);ꢀmeltingꢀpoint:ꢀ257–259ꢀ°Cꢀ(Ref.ꢀ[10]:ꢀ
1
2
56–257ꢀ°C);ꢀ HꢀNMRꢀ(300ꢀMHz,ꢀDMSO‐d
6
):ꢀδꢀ0.84ꢀ(s,ꢀ3H),ꢀ0.99ꢀ
100
(s,ꢀ3H),ꢀ1.97ꢀ(d,ꢀJꢀ=ꢀ16.0ꢀHz,ꢀ1H),ꢀ2.15ꢀ(d,ꢀJꢀ=ꢀ16.1ꢀHz,ꢀ1H),ꢀ2.28ꢀ
(
s,ꢀ 3H),ꢀ 2.37–2.49ꢀ (m,ꢀ 2H),ꢀ 3.52ꢀ (s,ꢀ 3H),ꢀ 3.66ꢀ (s,ꢀ 3H),ꢀ 4.81ꢀ (s,ꢀ
95
Pyridine
1
H),ꢀ6.73ꢀ(d,ꢀJꢀ=ꢀ7.4ꢀHz,ꢀ2H),ꢀ7.05ꢀ(d,ꢀJꢀ=ꢀ7.4ꢀHz,ꢀ2H),ꢀ9.02ꢀ(s,ꢀ1H);ꢀ
13CꢀNMRꢀ(75ꢀMHz,ꢀDMSO‐d
):ꢀδꢀ18.7,ꢀ26.9,ꢀ29.6,ꢀ32.6,ꢀ35.2,ꢀ50.7,ꢀ
1.1,ꢀ55.3,ꢀ104.0,ꢀ110.7,ꢀ113.6,ꢀ128.7,ꢀ140.3,ꢀ145.4,ꢀ149.7,ꢀ157.7,ꢀ
67.9,ꢀ194.7.ꢀ
Methylꢀ 4‐(3‐bromophenyl)‐2,7,7‐trimethyl‐5‐oxo‐
‐hexahydroquinoline‐3‐carboxylateꢀ(18).ꢀWhiteꢀsolid;ꢀisolatedꢀ
90
85
80
75
6
5
1
ꢀ
1,4,5,6,7,ꢀ
8
yieldꢀ 90%ꢀ (0.36ꢀ g);ꢀ meltingꢀ point:ꢀ 233–234ꢀ °Cꢀ (Ref.ꢀ [10]:ꢀ
100
1
6
235–236ꢀ°C);ꢀ HꢀNMRꢀ(300ꢀMHz,ꢀDMSO‐d ):ꢀδꢀ0.83ꢀ(s,ꢀ3H),ꢀ1.00ꢀ
90
3
[Pyridine-SO H]Cl
(s,ꢀ3H),ꢀ1.99ꢀ(d,ꢀJꢀ=ꢀ16.0ꢀHz,ꢀ1H),ꢀ2.18ꢀ(d,ꢀJꢀ=ꢀ16.1ꢀHz,ꢀ1H),ꢀ2.30ꢀ
(s,ꢀ3H),ꢀ2.39–2.49ꢀ(m,ꢀ2H),ꢀ3.53ꢀ(s,ꢀ3H),ꢀ4.85ꢀ(s,ꢀ1H),ꢀ7.14–7.16ꢀ
(
m,ꢀ 2H),ꢀ 7.25–7.27ꢀ (m,ꢀ 2H),ꢀ 9.15ꢀ (s,ꢀ 1H);ꢀ 13Cꢀ NMRꢀ (75ꢀ MHz,ꢀ
80
70
6
DMSO‐d ):ꢀ δꢀ 18.8,ꢀ 26.8,ꢀ 29.5,ꢀ 32.6,ꢀ 36.3,ꢀ 103.1,ꢀ 109.9,ꢀ 121.6,ꢀ
1
26.8,ꢀ 129.1,ꢀ 130.5,ꢀ 130.6,ꢀ 146.3,ꢀ 150.3,ꢀ 150.5,ꢀ 167.5,ꢀ 194.7;ꢀ
60
+
MS:ꢀm/zꢀ=ꢀ404ꢀ[M] ;ꢀCHNꢀAnalysis:ꢀAnal.ꢀCalcdꢀforꢀC20
Cꢀ59.42,ꢀHꢀ5.48,ꢀNꢀ3.46;ꢀFoundꢀCꢀ59.61,ꢀHꢀ5.27,ꢀNꢀ3.39.ꢀ
Diethylꢀ 4,4'‐(1,4‐phenylene)bis(2,7,7‐trimethyl‐5‐oxo‐
,7,8‐hexahydroquinoline‐3‐carboxylate)ꢀ (19).ꢀ Whiteꢀ solid;ꢀ
isolatedꢀ yieldꢀ 76%ꢀ (0.46ꢀ g);ꢀ meltingꢀ point:ꢀ 294–296ꢀ °C;ꢀ IRꢀ
3
H22BrNO :ꢀ
5
0
4
000 3500 3000 2500 2000 1500 1000
1
ꢀ
1,4,5,ꢀ
Wavenumber (cm )
Fig.ꢀ 1.ꢀ IRꢀ spectraꢀ ofꢀ sulfonicꢀ acidꢀ functionalizedꢀ pyridiniumꢀ chlorideꢀ
[pyridine‐SO H]Cl.ꢀ
6
3

ꢀ
ArdeshirꢀKhazaeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944ꢀ
ꢀ
(
a)
(b)
16
14
12
10

8
6
4
160 140 120 100 80
60
40
H]Cl.ꢀ
20

1
13
Fig.ꢀ2.ꢀ Hꢀ(a)ꢀandꢀ Cꢀ(b)ꢀNMRꢀspectraꢀofꢀsulfonicꢀacidꢀfunctionalizedꢀpyridiniumꢀchlorideꢀ[pyridine‐SO
3
theꢀ observedꢀ chemicalꢀ shiftsꢀ ofꢀ theꢀ acidicꢀ hydrogenꢀ inꢀ theseꢀ
threeꢀspeciesꢀconfirmedꢀthatꢀtheꢀpeakꢀdetectedꢀatꢀδꢀ=ꢀ13.67ꢀhadꢀ
temperaturesꢀviaꢀtheꢀdrop‐wiseꢀadditionꢀofꢀchlorosulfonicꢀacidꢀ
(1ꢀequiv.)ꢀtoꢀpyridineꢀ(2ꢀequiv.)ꢀ(Schemeꢀ3).ꢀUnderꢀtheseꢀcondi‐
tions,ꢀbecauseꢀpyridineꢀisꢀalwaysꢀpresentꢀinꢀexcessꢀcomparedꢀ
3
beenꢀ correctlyꢀ assignedꢀ toꢀ theꢀ SO Hꢀ groupꢀ ofꢀ theꢀ [pyri‐
dine‐SO H]Clꢀcatalyst.ꢀ
3
withꢀClSO
(asꢀaꢀnucleophile)ꢀattachesꢀtoꢀtheꢀsulfurꢀofꢀClSO
[pyridine‐SO H]Cl,ꢀwithꢀanotherꢀequiv.ꢀofꢀpyridineꢀfunctioningꢀ
3
H,ꢀitꢀisꢀgenerallyꢀassumedꢀthatꢀ1ꢀequiv.ꢀofꢀpyridineꢀ
TheꢀUV/Visꢀabsorbanceꢀspectrumꢀofꢀtheꢀcatalystꢀwasꢀcom‐
paredꢀwithꢀthoseꢀofꢀpyridineꢀandꢀpyridiniumꢀchlorideꢀtoꢀhigh‐
lightꢀtheꢀdifferencesꢀbetweenꢀtheꢀUV/Visꢀabsorbanceꢀpatternꢀofꢀ
theꢀcatalystꢀandꢀpyridiniumꢀchloride.ꢀAsꢀshownꢀinꢀFig.ꢀ3,ꢀλmaxꢀinꢀ
theꢀUV/Visꢀspectrumꢀofꢀtheꢀcatalystꢀappearedꢀatꢀaboutꢀ285ꢀnm.ꢀ
Inꢀ theꢀ UV/Visꢀ spectraꢀ ofꢀ pyridineꢀ andꢀ pyridiniumꢀ chloride,ꢀ
however,ꢀtheꢀλmaxꢀvaluesꢀappearedꢀatꢀaboutꢀ270ꢀandꢀ295ꢀnm,ꢀ
3
Hꢀtoꢀproduceꢀ
3
asꢀaꢀbaseꢀtoꢀabstractꢀtheꢀacidicꢀhydrogenꢀofꢀ[pyridine‐SO
3
H]Clꢀ
+
–.ꢀInꢀourꢀcurrentꢀprocedureꢀforꢀ
toꢀyieldꢀC
5
H
5
NHClꢀandꢀC
5
H
5
N SO
3
3
theꢀ synthesisꢀ ofꢀ [pyridine‐SO H]Cl,ꢀ 1ꢀ equiv.ꢀ ofꢀ pyridineꢀ wasꢀ
addedꢀdrop‐wiseꢀtoꢀ1ꢀequiv.ꢀofꢀchlorosulfonicꢀacidꢀatꢀlowꢀtem‐
perature.ꢀUnderꢀtheseꢀconditions,ꢀthereꢀisꢀalwaysꢀanꢀexcessꢀofꢀ
respectivelyꢀ (Theꢀ compoundsꢀ wereꢀ dissolvedꢀ inꢀ DMSO‐d
UVꢀstudiesꢀatꢀaꢀconcentrationꢀofꢀ0.005ꢀmol/L).ꢀ
WeꢀalsoꢀstudiedꢀtheꢀformationꢀofꢀanꢀN–Sꢀbondꢀbyꢀexposingꢀ
hydrogenꢀchlorideꢀgasꢀtoꢀsulfurꢀtrioxideꢀpyridineꢀcomplexꢀasꢀaꢀ
whiteꢀ solidꢀ powder.ꢀ Thisꢀ reactionꢀ alsoꢀ representsꢀ anꢀ alterna‐
6
ꢀ forꢀ
ClSO
whenꢀpyridineꢀreactsꢀwithꢀClSO
formedꢀ andꢀ thereꢀ wouldꢀ beꢀ noꢀ baseꢀ presentꢀ inꢀ theꢀ reactionꢀ
3
Hꢀinꢀtheꢀreactionꢀmixtureꢀcomparedꢀwithꢀpyridine.ꢀThus,ꢀ
3
H,ꢀ[pyridine‐SO H]Clꢀwouldꢀbeꢀ
3
+
–ꢀ
mixtureꢀtoꢀabstractꢀtheꢀacidicꢀhydrogenꢀtoꢀproduceꢀC
5
H
5
N SO
3
andꢀC NHCl.ꢀMoreover,ꢀbasedꢀonꢀresultsꢀfromꢀtheꢀliteratureꢀ
5 5
H
tiveꢀ methodꢀ forꢀ theꢀ preparationꢀ ofꢀ [pyridine‐SO
3
H]Cl,ꢀ whereꢀ
[15,48,49],ꢀtheꢀreactionꢀofꢀpyridineꢀwithꢀchlorosulfonicꢀacidꢀatꢀ
lowꢀ temperatureꢀ wouldꢀ occurꢀ viaꢀ aꢀ nucleophilicꢀ substitutionꢀ
1
theꢀwhiteꢀsolidꢀpowderꢀbecomesꢀaꢀviscousꢀcolorlessꢀoil.ꢀTheꢀ Hꢀ
andꢀ 13Cꢀ NMRꢀ andꢀ IRꢀ spectraꢀ ofꢀ theꢀ productꢀ wereꢀ comparedꢀ
withꢀthoseꢀobtainedꢀfromꢀtheꢀotherꢀprocedureꢀdescribedꢀaboveꢀ
andꢀ foundꢀ toꢀ beꢀ identical.ꢀ Thisꢀ resultꢀ clearlyꢀ provesꢀ thatꢀ theꢀ
pathwayꢀ(i.e.,ꢀsubstitutionꢀofꢀtheꢀClꢀinꢀClSO
pyridine)ꢀ ratherꢀthanꢀtheꢀacid‐baseꢀreactionꢀ(i.e.,ꢀ theꢀabstrac‐
tionꢀ ofꢀ theꢀ hydrogenꢀ ofꢀ ClSO Hꢀ byꢀ pyridineꢀ toꢀ affordꢀ
[C N‐H][ClSO ]).ꢀ
Theꢀ sulfonicꢀ acidꢀ functionalizedꢀ pyridiniumꢀ chlorideꢀ wasꢀ
3
Hꢀbyꢀtheꢀnitrogenꢀofꢀ
3
3
structureꢀofꢀtheꢀ[pyridine‐SO H]Clꢀpreparedꢀinꢀtheꢀcurrentꢀhasꢀ
H
5 5
3
beenꢀcorrectlyꢀcharacterizedꢀ(Schemeꢀ1).ꢀ
Moreover,ꢀ basedꢀ onꢀ theꢀ resultsꢀ fromꢀ theꢀ literatureꢀ
15,48,49],ꢀitꢀisꢀwellꢀknownꢀthatꢀsulfurꢀtrioxideꢀpyridineꢀcom‐
alsoꢀstudiedꢀbyꢀTGA.ꢀTheꢀcorrespondingꢀdiagramsꢀareꢀshownꢀinꢀ
Fig.ꢀ4.ꢀTGAꢀandꢀDTGAꢀofꢀtheꢀcatalystꢀshowedꢀthatꢀaꢀmassꢀlossꢀ
[
+
–]ꢀcanꢀbeꢀgeneratedꢀinꢀdichloromethaneꢀatꢀlowꢀ
plexꢀ[C
5
H
5
N SO
3
occurredꢀinꢀoneꢀstep.ꢀTheꢀ[pyridine‐SO
3
H]Clꢀdecomposedꢀafterꢀ
200ꢀ°Cꢀinꢀoneꢀstep.ꢀ
2
.0
.6
.2
.8
.4
.0
3
.2.ꢀ ꢀ Catalyticꢀactivityꢀofꢀ[pyridine‐SO H]Cl
3
1
1
0
0
0
Followingꢀ onꢀ fromꢀ ourꢀ fullꢀ characterizationꢀ ofꢀ [pyri‐
dine‐SO H]Cl,ꢀ weꢀ examinedꢀ itsꢀ catalyticꢀ activityꢀ towardsꢀ theꢀ
3
synthesisꢀofꢀhexahydroquinolines.ꢀTheꢀmulti‐componentꢀreac‐
tionꢀofꢀdimedoneꢀ(2ꢀmmol),ꢀ2‐methoxybenzaldehydeꢀ(2ꢀmmol),ꢀ
(1)
(2)
(3)
2
ClSO
3
H
Cl
N
N
N
2
60 270 280 290 300 310 320 330 340 350 360
H
Wavelength (nm)
SO3
Fig.ꢀ3.ꢀUVꢀspectraꢀofꢀpyridineꢀ(1),ꢀpyridiniumꢀchlorideꢀ(2),ꢀandꢀsulfonic
Schemeꢀ 3.ꢀ Preparationꢀ ofꢀ theꢀ sulfurꢀ trioxideꢀ pyridineꢀ complexꢀ
3
acidꢀfunctionalizedꢀpyridiniumꢀchlorideꢀ[pyridine‐SO H]Clꢀ(3)ꢀatꢀroom
temperatureꢀinꢀdimethylꢀsulfoxide.ꢀ
+
–
[C H
5 5
N SO ]ꢀbyꢀtheꢀreactionꢀofꢀpyridineꢀwithꢀchlorosulfonicꢀacid.
3

ꢀ
ArdeshirꢀKhazaeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944ꢀ
Tableꢀ2ꢀ
100
(a)
Effectꢀ ofꢀ differentꢀ solventsꢀ onꢀ theꢀ reactionꢀ ofꢀ dimedone,ꢀ 2‐
ꢀ
methox‐
8
6
4
2
0
0
0
0
ybenzaldehyde,ꢀethylꢀacetoacetate,ꢀandꢀammoniumꢀacetateꢀinꢀtheꢀpres‐
enceꢀofꢀ[pyridine‐SO
Entryꢀ Solventꢀ
CHCl
3
H]Clꢀ(1ꢀmol%).ꢀ
ꢀ
a
Temperatureꢀ(°C)ꢀ Timeꢀ(min)
Yield ꢀ(%)
38ꢀ
1ꢀ
3
ꢀ
50ꢀ
50ꢀ
50ꢀ
50ꢀ
refluxꢀ
50ꢀ
60ꢀ
60ꢀ
60ꢀ
60ꢀ
60ꢀ
11ꢀ
2
3ꢀ
ꢀ
EtOAcꢀ
EtOHꢀ
45ꢀ
41ꢀ
48ꢀ
42ꢀ
4
5ꢀ
ꢀ
hexaneꢀ
CH Cl ꢀ
700
600
500
400
300
200
100
0
2
2
(b)
6ꢀ
—ꢀ
96ꢀ
aꢀIsolatedꢀyield.
dehydeꢀasꢀwellꢀasꢀarylaldehydeꢀpossessingꢀelectron‐withdraw‐
ꢀ
ingꢀ groups,ꢀ electron‐donatingꢀ groups,ꢀ andꢀ halogens),ꢀ
β‐ketoestersꢀ(ethylꢀandꢀ methylꢀacetoacetate),ꢀ andꢀammoniumꢀ
acetateꢀ underꢀ theꢀ optimizedꢀ reactionꢀ conditions.ꢀ Theꢀ resultsꢀ
areꢀshownꢀinꢀTableꢀ3.ꢀItꢀisꢀclearꢀthatꢀallꢀofꢀreactionsꢀproceededꢀ
efficientlyꢀunderꢀtheꢀoptimizedꢀconditionsꢀtoꢀaffordꢀtheꢀcorre‐
spondingꢀhexahydroquinolinesꢀinꢀhighꢀyieldsꢀoverꢀshortꢀreac‐
0
100
200
300
400
500
600
o
Temperature ( C)
Fig.ꢀ4.ꢀTGAꢀ(a)ꢀandꢀDTGAꢀ(b)ꢀdiagramsꢀofꢀtheꢀ[pyridine‐SO
3
H]Clꢀcata‐
tionꢀ time.ꢀ Thus,ꢀ ourꢀ newꢀ ionicꢀ liquidꢀ [pyridine‐SO H]Clꢀ isꢀ aꢀ
3
lyst.ꢀ
highlyꢀefficientꢀandꢀgeneralꢀcatalystꢀforꢀtheꢀsynthesisꢀofꢀHHQs.ꢀ ꢀ
Itꢀisꢀimportantꢀthatꢀionicꢀliquidsꢀandꢀionicꢀliquidsꢀsupportedꢀ
onꢀsolidsꢀpossessꢀgoodꢀrecyclabilityꢀpropertiesꢀ[5,15,16].ꢀWithꢀ
ethylꢀ acetoacetateꢀ (2ꢀ mmol),ꢀ andꢀ ammoniumꢀ acetateꢀ (2.4ꢀ
mmol)ꢀ wasꢀ selectedꢀ asꢀ aꢀ modelꢀ reaction.ꢀ Theꢀ reactionꢀ wasꢀ
conductedꢀ inꢀ theꢀ presenceꢀ ofꢀ differentꢀ amountsꢀ ofꢀ [pyri‐
thisꢀ inꢀ mind,ꢀ weꢀ assessedꢀ theꢀ recyclabilityꢀ ofꢀ theꢀ [pyridine‐
SO H]Clꢀionicꢀliquidꢀinꢀtermsꢀofꢀitsꢀapplicationꢀasꢀaꢀcatalystꢀ(3ꢀ
mol%)ꢀtoꢀtheꢀmulti‐componentꢀreactionꢀofꢀdimedoneꢀ(2ꢀmmol),ꢀ
‐methoxybenzaldehydeꢀ (2ꢀ mmol),ꢀ methylꢀ acetoacetateꢀ (2ꢀ
ꢀ
3
dine‐SO H]Clꢀatꢀtemperaturesꢀinꢀtheꢀrangeꢀofꢀ25ꢀtoꢀ90ꢀ°Cꢀinꢀtheꢀ
3
absenceꢀ ofꢀ solvent.ꢀ Theꢀ resultsꢀ ofꢀ theseꢀ optimizationꢀ experi‐
mentsꢀareꢀsummarizedꢀinꢀTableꢀ1.ꢀItꢀisꢀclearꢀfromꢀtheꢀresultsꢀ
thatꢀ aꢀ catalystꢀ loadingꢀ ofꢀ 3ꢀ mol%ꢀ wasꢀ sufficientꢀ toꢀ efficientlyꢀ
catalyzeꢀ theꢀ reactionꢀ atꢀ 50ꢀ °C,ꢀ withꢀ theꢀ correspondingꢀ HHQꢀ
beingꢀobtainedꢀinꢀ96%ꢀyieldꢀunderꢀtheseꢀconditionsꢀwithinꢀ11ꢀ
minꢀ(Tableꢀ1,ꢀentryꢀ3).ꢀ
Theꢀ reactionꢀ ofꢀ dimedoneꢀ (2ꢀ mmol),ꢀ 2‐
hydeꢀ (2ꢀ mmol),ꢀ ethylꢀ acetoacetateꢀ (2ꢀ mmol),ꢀ andꢀ ammoniumꢀ
acetateꢀ (2.4ꢀ mmol)ꢀ inꢀ theꢀ presenceꢀ ofꢀ [pyridine‐SO H]Clꢀ wasꢀ
2
mmol),ꢀandꢀammoniumꢀacetateꢀ(2.4ꢀmmol)ꢀatꢀ50ꢀ°C.ꢀUponꢀcom‐
pletionꢀofꢀtheꢀreaction,ꢀtheꢀreactionꢀmixtureꢀwasꢀcooledꢀtoꢀroomꢀ
temperatureꢀ andꢀ dilutedꢀ withꢀ ethylꢀ acetateꢀ (20ꢀ mL).ꢀ Theꢀ re‐
sultingꢀ mixtureꢀ wasꢀ stirredꢀ underꢀ refluxꢀ forꢀ 3ꢀ minꢀ andꢀ thenꢀ
decantedꢀ(theꢀproductꢀwasꢀsolubleꢀinꢀhotꢀethylꢀacetate,ꢀwhereasꢀ
theꢀ catalystꢀ wasꢀ insoluble).ꢀ Theꢀ viscousꢀ oilyꢀ residueꢀ wasꢀ
washedꢀ withꢀ hotꢀ ethylꢀ acetateꢀ (10ꢀ mL)ꢀ andꢀ driedꢀ toꢀ giveꢀ theꢀ
pureꢀrecycledꢀcatalyst,ꢀwhichꢀwasꢀusedꢀforꢀtheꢀnextꢀrunꢀofꢀtheꢀ
ꢀ
methoxybenzalde‐
3
selectedꢀ asꢀ aꢀ modelꢀ reactionꢀ toꢀ compareꢀ theꢀ efficiencyꢀ ofꢀ theꢀ
solutionꢀ versusꢀ solvent‐freeꢀ conditionsꢀ usingꢀ aꢀ varietyꢀ ofꢀ dif‐
ferentꢀsolventsꢀatꢀ50ꢀ°C.ꢀAllꢀofꢀtheꢀsolventsꢀtestedꢀprovidedꢀlowꢀ
yieldsꢀofꢀtheꢀproduct,ꢀevenꢀafterꢀextendedꢀreactionꢀtimeꢀ(Tableꢀ
reaction.ꢀ Theꢀ catalyticꢀ activityꢀ ofꢀ [pyridine‐SO
H]Clꢀ wasꢀ re‐
storedꢀ toꢀ withinꢀ theꢀ limitsꢀ ofꢀ theꢀ experimentalꢀ errorꢀ forꢀ fourꢀ
successiveꢀrunsꢀ(seeꢀTableꢀ4).ꢀ
Aꢀmechanismꢀhasꢀbeenꢀproposedꢀforꢀtheꢀreactionꢀasꢀshownꢀ
inꢀSchemeꢀ4.ꢀThus,ꢀtheꢀconversionꢀofꢀdimedoneꢀtoꢀitsꢀenolꢀformꢀ
3
2).ꢀ
Toꢀassessꢀtheꢀgeneralꢀscopeꢀofꢀtheꢀnewꢀcatalyst,ꢀdimedoneꢀ
usingꢀ [pyridine‐SO H]Clꢀandꢀitsꢀsubsequentꢀ reactionꢀ withꢀtheꢀ
3
wasꢀreactedꢀwithꢀaꢀseriesꢀofꢀdifferentꢀarylꢀaldehydesꢀ(benzal‐
activatedꢀ aldehydeꢀ (activatedꢀ byꢀ theꢀ catalyst)ꢀ wouldꢀ giveꢀ in‐
termediateꢀ I.ꢀ Inꢀ contrast,ꢀ theꢀ reactionꢀ ofꢀ theꢀ activatedꢀ
β‐ketoesterꢀ(activatedꢀbyꢀtheꢀcatalyst)ꢀwithꢀammoniaꢀ(resultedꢀ
fromꢀammoniumꢀacetate)ꢀwouldꢀgiveꢀenamineꢀII.ꢀTheꢀreactionꢀ
ofꢀintermediateꢀIꢀwithꢀenamineꢀIIꢀwouldꢀthenꢀaffordꢀintermedi‐
ateꢀ III,ꢀ whichꢀ wouldꢀ beꢀ convertedꢀ toꢀ IVꢀ byꢀ tautomerization.ꢀ
Thisꢀ intermediateꢀ wouldꢀ thenꢀ undergoꢀ anꢀ intramolecularꢀ nu‐
Tableꢀ1ꢀ
Effectꢀofꢀtheꢀ[pyridine‐SO H]Clꢀcatalystꢀamountꢀandꢀtemperatureꢀonꢀtheꢀ
3
reactionꢀ betweenꢀ dimedone,ꢀ 2‐methoxybenzaldehyde,ꢀ ethylꢀ acetoace‐
tate,ꢀandꢀammoniumꢀacetateꢀinꢀtheꢀabsenceꢀofꢀsolvent.ꢀ
ꢀa
Catalystꢀloadingꢀ
Temperatureꢀ ꢀ
(°C)ꢀ
Timeꢀ
(min)ꢀ
Yield ꢀ
(%)ꢀ
Entryꢀ
(mol%)ꢀ
cleophilicꢀattackꢀfromꢀtheꢀNH
2
ꢀgroupꢀtoꢀtheꢀactivatedꢀcarbonylꢀ
1
2ꢀ
ꢀ
1ꢀ
2ꢀ
3ꢀ
5ꢀ
3ꢀ
3ꢀ
3ꢀ
50ꢀ
50ꢀ
50ꢀ
50ꢀ
25ꢀ
70ꢀ
90ꢀ
25ꢀ
15ꢀ
11ꢀ
11ꢀ
15ꢀ
11ꢀ
11ꢀ
61ꢀ
73ꢀ
96ꢀ
96ꢀ
78ꢀ
96ꢀ
96ꢀ
groupꢀwithꢀtheꢀlossꢀofꢀH OꢀtoꢀaffordꢀV.ꢀTheꢀtautomerizationꢀofꢀVꢀ
2
wouldꢀthenꢀgiveꢀtheꢀobservedꢀhexahydroquinolineꢀproduct.ꢀItꢀisꢀ
noteworthyꢀthatꢀinꢀtheꢀstepsꢀinvolvingꢀtheꢀactivationꢀofꢀcarbon‐
ylꢀ groupsꢀ throughꢀ theꢀ donationꢀ ofꢀ aꢀ protonꢀ fromꢀ theꢀ [pyri‐
3
ꢀ
4
ꢀ
5
ꢀ
dine‐SO H]Cl,ꢀtheꢀprotonꢀwouldꢀbeꢀtransferredꢀbackꢀtoꢀtheꢀcat‐
3
6
ꢀ
alystꢀ inꢀ aꢀ laterꢀ step.ꢀ Thisꢀ mechanismꢀ canꢀ thereforeꢀ beꢀ con‐
firmedꢀbyꢀtheꢀliteratureꢀ[39,41,43].ꢀ
7ꢀ
aꢀIsolatedꢀyield.ꢀ

ꢀ
ArdeshirꢀKhazaeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944ꢀ
ꢀ
Tableꢀ3ꢀ
Theꢀsolvent‐freeꢀsynthesisꢀofꢀHHQsꢀfromꢀdimedone,ꢀarylaldehydes,ꢀβ‐ketoesters,ꢀandꢀammoniumꢀacetateꢀcatalyzedꢀbyꢀ[pyridine‐SO
3
H]Clꢀatꢀ50ꢀ°C.ꢀ
Timeꢀ Yieldꢀaꢀ
min)ꢀ (%)ꢀ
Meltingꢀpointꢀ(°C)ꢀ
(Ref.)ꢀ
Timeꢀ Yieldꢀaꢀ Meltingꢀpointꢀ(°C)ꢀ
Aldehydeꢀ
Productꢀ
ꢀ
Aldehydeꢀ
Productꢀ
ꢀ
(
(min)ꢀ (%)ꢀ
(Ref.)ꢀ
Cl
Cl
O
O
2
06–208ꢀ
Cl
O
243–245ꢀ
ꢀ
CHO
1ꢀ
12ꢀ
8ꢀ
94ꢀ
95ꢀ
O
11
12
10ꢀ
12ꢀ
94ꢀ
92ꢀ
ꢀ
OEt
(203–205ꢀ[30])ꢀ
Cl
CHO
OEt
N
H
ꢀ
N
H
NO2
245–248ꢀ
CHO
O
O
O
O
O
2
N
CHO
2ꢀ
235–237ꢀ
211–213ꢀ
ꢀ
(242–244ꢀ[34])ꢀ
OEt
OEt
N
H
N
H
ꢀ
NO
O
2
OH
O
O
2
N
HO
O
O
179–181ꢀ
3ꢀ
10ꢀ
10ꢀ
94ꢀ
95ꢀ
13
14
8ꢀ
92ꢀ
91ꢀ
CHO
OEt
OEt
OEt
CHO
OEt
(
177–178ꢀ[32])ꢀ
ꢀ
ꢀ
N
H
N
H
ꢀ
OMe
261–263ꢀ
O
O
256–258ꢀ
O
O
MeO
CHO
4ꢀ
CHO
13ꢀ
(260–262ꢀ[10])
ꢀ
ꢀ
(257–259ꢀ[33])ꢀ
ꢀ
OMe
N
N
H
H
ꢀ
Me
NO
O
2
O
2
N
230–232ꢀ
(229–231ꢀ[10])
ꢀ
O
259–262ꢀ
O
O
Me
CHO
5ꢀ
8ꢀ
8ꢀ
92ꢀ
94ꢀ
15
16
12ꢀ
11ꢀ
92ꢀ
90ꢀ
ꢀ
CHO
(260–261ꢀ[33])ꢀ
OMe
N
H
N
H
ꢀ
OH
Me
234–236ꢀ
282–284ꢀ
ꢀ
O
O
O
O
HO
CHO
6ꢀ
Me
CHO
ꢀ
(232–234ꢀ[33])ꢀ
OEt
OMe
N
H
N
H
ꢀ
Br
OMe
2
57–259ꢀ
2
52–254ꢀ
O
O
O
O
Br
CHO
7ꢀ
10ꢀ
8ꢀ
91ꢀ
90ꢀ
MeO
CHO
17
18
12ꢀ
5ꢀ
91ꢀ
90ꢀ
(256–27ꢀ[10])ꢀ
ꢀ
ꢀ
(255–257ꢀ[30])ꢀ
OEt
OMe
N
H
N
H
ꢀ
Br
O
Br
O
Br
Br
O
O
235–236ꢀ
233–234ꢀ
(235–236ꢀ[10])
8ꢀ
CHO
OEt
CHO
(
235–237ꢀ[30])ꢀ
OMe
ꢀ
ꢀ
N
H
N
H
ꢀ
H
N
Cl
OEt
OEt
O
O
O
2
44–246ꢀ
294–296ꢀ
ꢀ
O
O
Cl
CHO
9ꢀ
10ꢀ
91ꢀ
96ꢀ
OHC
CHO
19
8ꢀ
ꢀ
76ꢀ
ꢀ
ꢀ
(245–246ꢀ[32])ꢀ
OEt
O
N
H
ꢀ
N
ꢀ
ꢀ
ꢀ
ꢀ
OMe
CHO
OMe
O
O
257–259ꢀ
256–257ꢀ[10])ꢀ
10ꢀ 11ꢀ
(
ꢀ
OEt
N
H
ꢀ
aꢀIsolatedꢀyield.ꢀ

ꢀ
ArdeshirꢀKhazaeiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ34ꢀ(2013)ꢀ1936–1944ꢀ
Wiley‐VCH,ꢀ2008ꢀ
5] HasaninejadꢀA,ꢀZareꢀA,ꢀShekouhyꢀM,ꢀAmeriꢀRadꢀJ.ꢀJꢀCombꢀChem,ꢀ
Tableꢀ4ꢀ
[
[
[
Theꢀ condensationꢀ ofꢀ dimedoneꢀ withꢀ 2‐methoxybenzaldehyde,ꢀ ethylꢀ
acetoacetate,ꢀandꢀammoniumꢀacetateꢀusingꢀrecycledꢀ[pyridine‐SO
2010,ꢀ12:ꢀ844ꢀ
3
H]Cl.
6] Zareꢀ A,ꢀ Parhamiꢀ A,ꢀ Moosavi‐Zareꢀ Aꢀ R,ꢀ Hasaninejadꢀ A,ꢀ Khala‐
fi‐NezhadꢀA,ꢀBeyzaviꢀMꢀH.ꢀCanꢀJꢀChem,ꢀ2009,ꢀ87:ꢀ416ꢀ
7] EichmannꢀM,ꢀKeimꢀW,ꢀHaumannꢀM,ꢀMelcherꢀBꢀU,ꢀWasserscheidꢀP.ꢀJꢀ
MolꢀCatalꢀA,ꢀ2009,ꢀ314:ꢀ42ꢀ
8] KimꢀYꢀJ,ꢀVarmaꢀRꢀS.ꢀTetrahedronꢀLett,ꢀ2005,ꢀ46:ꢀ1467ꢀ
9] ÖchsnerꢀE,ꢀSchneiderꢀMꢀJ,ꢀMeyerꢀC,ꢀHaumannꢀM,ꢀWasserscheidꢀP.ꢀ
ApplꢀCatalꢀA,ꢀ2011,ꢀ399:ꢀ35ꢀ
a
Runꢀ
Timeꢀ(min)ꢀ
Yieldꢀ ꢀ(%)ꢀ
1
ꢀ
96ꢀ
93ꢀ
90ꢀ
85ꢀ
11ꢀ
13ꢀ
10ꢀ
15ꢀ
2
ꢀ
3
ꢀ
[
4
ꢀ
[
aꢀYieldꢀofꢀpurifiedꢀproduct.
[
10] ZareꢀA,ꢀAbiꢀF,ꢀMoosavi‐ZareꢀAꢀR,ꢀBeyzaviꢀMꢀH,ꢀZolfigolꢀMꢀA.ꢀJꢀMolꢀ
O
O
O
Cl
N
S O
Liq,ꢀ2013,ꢀ178:ꢀ113ꢀ
H
O
S
N
Cl
O
O
S
N
Cl
O
H
H
[11] ShaterianꢀHꢀR,ꢀRanjbarꢀM.ꢀJꢀMolꢀLiq,ꢀ2011,ꢀ160:ꢀ40ꢀ
[12] ZolfigolꢀMꢀA,ꢀKhakyzadehꢀV,ꢀMoosavi‐ZareꢀAꢀR,ꢀZareꢀA,ꢀAzimiꢀSꢀB,ꢀ
AsgariꢀZ,ꢀHasaninejadꢀA.ꢀCꢀRꢀChim,ꢀ2012,ꢀ15:ꢀ719ꢀ
[13] ZolfigolꢀMꢀA,ꢀKhazaeiꢀA,ꢀMoosavi‐ZareꢀAꢀR,ꢀZareꢀA.ꢀJꢀIranꢀChemꢀSoc,ꢀ
2010,ꢀ7:ꢀ646ꢀ
[14] ShaterianꢀHꢀR,ꢀRanjbarꢀM,ꢀAziziꢀK.ꢀJꢀMolꢀLiq,ꢀ2011,ꢀ162:ꢀ95ꢀ
[15] Zareꢀ A,ꢀ Moosavi‐Zareꢀ Aꢀ R,ꢀ Merajoddinꢀ M,ꢀ Zolfigolꢀ Mꢀ A,ꢀ
Hekmat‐Zadehꢀ T,ꢀ Hasaninejadꢀ A,ꢀ Khazaeiꢀ A,ꢀ Mokhlesiꢀ M,ꢀ Kha‐
kyzadehꢀV,ꢀDerakhshan‐PanahꢀF,ꢀBeyzaviꢀMꢀH,ꢀRostamiꢀE,ꢀArghoonꢀ
A,ꢀRoohandehꢀR.ꢀJꢀMolꢀLiq,ꢀ2012,ꢀ167:ꢀ69ꢀ ꢀ
O
O
O
O
O
O
Ar
H
Ar
H
OR
OR
H
2
N
-
H
2
O
- H O
2
O
O
O
(I)
(II)
H
H
H
N
H
O
Ar
O
HOAc
4
NH OAc
O
OR
O
O
HN
HO
OR
O
(III)
O
Ar
O
O
Ar
O
[16] ZolfigolꢀMꢀA,ꢀKhazaeiꢀA,ꢀMoosavi‐ZareꢀAꢀR,ꢀZareꢀA,ꢀKhakyzadehꢀV.ꢀ
ApplꢀCatalꢀA,ꢀ2011,ꢀ400:ꢀ70ꢀ
[17] ZolfigolꢀMꢀA,ꢀKhazaeiꢀA,ꢀMoosavi‐ZareꢀAꢀR,ꢀZareꢀA.ꢀOrgꢀPrepꢀProcedꢀ
Int,ꢀ2010,ꢀ42:ꢀ95ꢀ
OR
OR
O
Ar
O
H
H
2
N
N
H
O
H
-
H
2
O
OR
Hexahydroquinoline
(
IV)
N
H
V)
[18] Zolfigolꢀ Mꢀ A,ꢀ Khazaeiꢀ A,ꢀ Moosavi‐Zareꢀ Aꢀ R,ꢀ Zareꢀ A,ꢀ Krugerꢀ Hꢀ G,ꢀ
(
AsgariꢀZ,ꢀKhakyzadehꢀV,ꢀKazem‐RostamiꢀM.ꢀJꢀOrgꢀChem,ꢀ2012,ꢀ77:ꢀ
Schemeꢀ4.ꢀProposedꢀmechanismꢀforꢀtheꢀsynthesisꢀofꢀhexahydroquino‐
linesꢀpromotedꢀbyꢀ[pyridine‐SO H]Cl.ꢀ
3
640ꢀ
19] ZhuꢀJ,ꢀBienaymeꢀH.ꢀMulticomponentꢀReactions.ꢀWeinheim:ꢀWiley,ꢀ
005ꢀ
3
[
2
4.ꢀ ꢀ Conclusions
[20] KhazaeiꢀA,ꢀZolfigolꢀMꢀA,ꢀMoosavi‐ZareꢀAꢀR,ꢀZareꢀA,ꢀKhojastehꢀM,ꢀ
AsgariꢀZ,ꢀKhakyzadehꢀV,ꢀKhalafi‐NezhadꢀA.ꢀCatalꢀCommun,ꢀ 2012,ꢀ
2
0:ꢀ54ꢀ
WeꢀhaveꢀintroducedꢀtheꢀBrönstedꢀacidicꢀionicꢀliquidꢀ[pyri‐
dine‐SO H]Clꢀasꢀaꢀnovel,ꢀhighlyꢀefficient,ꢀgeneral,ꢀandꢀhomoge‐
[
21] Khazaeiꢀ A,ꢀ Zolfigolꢀ Mꢀ A,ꢀ Moosavi‐Zareꢀ Aꢀ R,ꢀ Zareꢀ A,ꢀ Parhamiꢀ A,ꢀ
Khalafi‐NezhadꢀA.ꢀApplꢀCatalꢀA,ꢀ2010,ꢀ386:ꢀ179ꢀ
22] GlassꢀBꢀD,ꢀBrownꢀMꢀE,ꢀDrummondꢀPꢀM.ꢀIn:ꢀAlbiniꢀA,ꢀFasaniꢀEꢀeds.ꢀ
Drugs:ꢀPhotochemistryꢀandꢀPhotostability.ꢀCambridge:ꢀTheꢀRoyalꢀ
SocietyꢀofꢀChemistry,ꢀ1998.ꢀ134ꢀ
23] BeijersbergenꢀvanꢀHenegouwenꢀGꢀMꢀJ.ꢀIn:ꢀTestaꢀB,ꢀMeyerꢀUꢀAꢀeds.ꢀ
Advancesꢀ inꢀ Drugꢀ Research.ꢀ Volꢀ 29.ꢀ London:ꢀ Academicꢀ Press,ꢀ
1997.ꢀ79ꢀ
[24] [24]ꢀGörlitzerꢀK,ꢀBaltruschꢀHꢀJ,ꢀGossnitzerꢀE,ꢀWendelinꢀW.ꢀPharma‐
zie,ꢀ2000,ꢀ55:ꢀ35ꢀ
3
neousꢀ catalystꢀ forꢀ theꢀ one‐potꢀ multi‐componentꢀ reactionꢀ ofꢀ
dimedone,ꢀ aromaticꢀ aldehydes,ꢀ β‐ketoesters,ꢀ andꢀ ammoniumꢀ
acetateꢀleadingꢀtoꢀhexahydroquinolines.ꢀTheꢀadvantagesꢀofꢀtheꢀ
currentꢀprotocolꢀincludeꢀitsꢀefficiency,ꢀbroadꢀscope,ꢀhighꢀprod‐
uctꢀyields,ꢀshortꢀreactionꢀtime,ꢀcleanꢀreactionꢀprofile,ꢀsimplicity,ꢀ
lowꢀcost,ꢀeaseꢀofꢀpreparation,ꢀandꢀtheꢀrecyclabilityꢀofꢀtheꢀcata‐
lyst.ꢀ
[
[
[
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O
O
OR
O
O
O
Ar
O
H
4
NH OAc
Ar
(
3 mol%)
OR
O
N
H
Solvent-free
o
5
0 C
1
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R = Me, Et
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