An efficient and reusable polymer-supported palladium catalyst for the Suzuki cross-coupling reactions of aryl halides

Article abstract of DOI:10.3184/030823409X12594170566203

A reusable, air-stable polymer-anchored palladium (II) Schiff base complex catalyst, P-[{(NCH)C₆H₄}Pd(OAc)]₂ was prepared and was found to be highly active in Suzuki cross-coupling reactions of aryl halides with phenyl boronic acid in an aqueous medium to give biaryl products in high yields.

Full text of DOI:10.3184/030823409X12594170566203

7
56ꢀ RESEARCH PAPER
DECEMBER,ꢀ756–760ꢀ
JOURNALꢀOFꢀCHEMICALꢀRESEARCHꢀ2009
An efficient and reusable polymer-supported palladium catalyst for the
Suzuki cross-coupling reactions of aryl halides
a
a
a
a
a
S.M. Islam *, P. Mondal , A. Singha Roy , S. Mondal and M. Mobarak
a
Department of Chemistry, University of Kalyani, Kalyani, Nadia, 741235, W.B., India
Aꢀreusable,ꢀair-stableꢀpolymer-anchoredꢀpalladiumꢀ(II)ꢀSchiffꢀbaseꢀcomplexꢀcatalyst,ꢀP-[{(NCH)C H }Pd(OAc)] wasꢀ
6
4
2ꢀ
preparedꢀandꢀwasꢀfoundꢀtoꢀbeꢀhighlyꢀactiveꢀinꢀSuzukiꢀcross-couplingꢀreactionsꢀofꢀarylꢀhalidesꢀwithꢀphenylꢀboronicꢀ
acidꢀinꢀanꢀaqueousꢀmediumꢀtoꢀgiveꢀbiarylꢀproductsꢀinꢀhighꢀyields.
Keywords: palladiumꢀcomplex,ꢀSuzukiꢀcross-couplingꢀreaction,ꢀbiaryls,ꢀarylꢀhalides
Theꢀ palladiumꢀ catalysedꢀ Suzukiꢀ cross-couplingꢀ reactionꢀ
hasꢀbecomeꢀaꢀversatileꢀtoolꢀinꢀmodernꢀorganicꢀsynthesisꢀforꢀ
theꢀ formationꢀ ofꢀ symmetricalꢀ andꢀ unsymmetricalꢀ biarylꢀ
compounds.1 ꢀCompoundsꢀcontainingꢀtheꢀbiarylꢀlinkageꢀareꢀ
anꢀimportantꢀclassꢀofꢀorganicꢀcompoundsꢀandꢀhaveꢀwidespreadꢀ
applicationsꢀ inꢀ manyꢀ areasꢀ ofꢀ organicꢀ synthesis,ꢀ naturalꢀ
productꢀsynthesis,ꢀpolymerꢀscienceꢀandꢀinꢀmaterialꢀscienceꢀasꢀ
precursorsꢀtoꢀmolecularꢀwiresꢀandꢀrigidꢀliquidꢀcrystals.
couplingꢀreactionsꢀofꢀvariousꢀsubstitutedꢀandꢀnon-substitutedꢀ
1
8-27
arylꢀhalides.
ꢀTheseꢀcomplexesꢀareꢀinsoluble,ꢀreusableꢀandꢀ
stableꢀinꢀairꢀandꢀmoisture.ꢀRecently,ꢀaqueousꢀphaseꢀreactionsꢀ
haveꢀ beenꢀ oneꢀ ofꢀ theꢀ majorꢀ interestsꢀ inꢀ organicꢀ synthesis,ꢀ
becauseꢀwaterꢀisꢀaꢀreadilyꢀavailable,ꢀsafe,ꢀandꢀenvironment-
-4
2
8
friendlyꢀ solvent. ꢀ Weꢀ nowꢀ describeꢀ aꢀ trulyꢀ heterogeneousꢀ
palladiumꢀcatalystꢀthatꢀisꢀveryꢀeffectiveꢀforꢀtheꢀSuzukiꢀcross-
couplingꢀ reactionꢀ betweenꢀ arylꢀ halidesꢀ andꢀ phenylꢀ boronicꢀ
Usuallyꢀ inꢀ Suzukiꢀ cross-couplingꢀ reactions,ꢀ arylꢀ halidesꢀ
reactꢀwithꢀarylꢀboronicꢀacidsꢀinꢀtheꢀpresenceꢀofꢀaꢀPdꢀcatalystꢀ
andꢀ aꢀ suitableꢀ baseꢀ inꢀ aꢀ singleꢀ stepꢀ underꢀ mildꢀ conditions.ꢀ
Manyꢀ activeꢀ catalyticꢀ systemsꢀ haveꢀ beenꢀ developedꢀ forꢀ theꢀ
Suzukiꢀ cross-couplingꢀ reactions.ꢀ Homogeneousꢀ phosphineꢀ
ligandsꢀ canꢀ beꢀ usedꢀ toꢀ complexꢀ theꢀ palladiumꢀ species,ꢀ
resultingꢀinꢀexcellentꢀresults.5 ꢀHowever,ꢀthisꢀtypeꢀofꢀcatalystꢀ
isꢀ sensitiveꢀ toꢀ moistureꢀ andꢀ airꢀ oxidationꢀ andꢀ thereforeꢀ
requiresꢀ air-freeꢀ handlingꢀ toꢀ minimiseꢀ ligandꢀ oxidation.ꢀ
Moreover,ꢀ homogeneousꢀ catalysisꢀ presentsꢀ problemsꢀ inꢀ
separationꢀandꢀwasteꢀinorganicꢀmaterialsꢀareꢀdifficultꢀtoꢀreuse.ꢀ
Deactivationꢀofꢀsolubleꢀpalladiumꢀcatalystsꢀbyꢀformationꢀofꢀ
inactiveꢀ particlesꢀ isꢀ alsoꢀ oftenꢀ encounteredꢀ atꢀ highꢀ reactionꢀ
temperatures.ꢀToꢀovercomeꢀtheseꢀproblems,ꢀtheꢀdevelopmentꢀ
ofꢀ solid-supportedꢀ andꢀ insolubleꢀ transitionꢀ metalꢀ catalystsꢀ
acidꢀinꢀaꢀH O–DMFꢀ(1ꢀ:ꢀ1)ꢀmedium.ꢀTheꢀpolymer-supportedꢀ
2
catalystꢀ wasꢀ moreꢀ activeꢀ thanꢀ theꢀ homogeneousꢀ analogue.ꢀ
Theꢀ catalystꢀ isꢀ air-stableꢀ andꢀ canꢀ beꢀ reusedꢀ severalꢀ timesꢀ
withoutꢀnoticeableꢀlossꢀofꢀcatalyticꢀactivity.
Theꢀpreparationꢀprocedureꢀfollowedꢀtoꢀobtainꢀtheꢀcatalystꢀisꢀ
givenꢀinꢀSchemeꢀ1.ꢀItꢀwasꢀreadilyꢀpreparedꢀinꢀtwoꢀsteps.ꢀFirst,ꢀ
theꢀaminoꢀpolystyreneꢀwasꢀtreatedꢀwithꢀPhCHOꢀtoꢀproduceꢀ
theꢀ correspondingꢀ Schiffꢀ baseꢀ whichꢀ wasꢀ thenꢀ reactedꢀ
withꢀPd(II)ꢀacetateꢀinꢀaceticꢀacidꢀtoꢀyieldꢀtheꢀcatalystꢀasꢀdarkꢀ
brownꢀsolid.
-8
Theꢀcharacterisationꢀofꢀtheꢀcatalystꢀwasꢀdoneꢀonꢀtheꢀbasisꢀ
ofꢀIRꢀspectroscopy,ꢀtheꢀdiffuseꢀreflectanceꢀspectraꢀofꢀtheꢀsolid,ꢀ
thermogravimetricꢀanalysisꢀandꢀbyꢀusingꢀaꢀscanningꢀelectronꢀ
microscope.ꢀ Theꢀ metalꢀ contentꢀ inꢀ theꢀ catalystꢀ determinedꢀ
byꢀ atomicꢀ absorptionꢀ spectroscopyꢀ suggestsꢀ 2.23%ꢀ Pdꢀ inꢀ
theꢀ immobilisedꢀ metalꢀ complex.ꢀ Theꢀ polymer-anchoredꢀ
Schiffꢀ baseꢀ Pd(II)ꢀ complexꢀ exhibitedꢀ importantꢀ IRꢀ peaksꢀ
9
,10
hasꢀattractedꢀaꢀgreatꢀdealꢀofꢀattentionꢀinꢀorganicꢀchemistry.
ꢀ
Dueꢀ toꢀ theirꢀ versatileꢀ processingꢀ capabilitiesꢀ andꢀ easeꢀ ofꢀ
separation,ꢀ longꢀ termꢀ stabilityꢀ inꢀ airꢀ andꢀ moistureꢀ andꢀ
recycling,ꢀ supportedꢀ catalystsꢀ offerꢀ manyꢀ advantagesꢀ forꢀ
-
1
-1
-1
atꢀ1615ꢀcm ꢀ(nꢀ–C=N-ꢀcoordinated),ꢀ1585ꢀcm ,ꢀ1430ꢀcm ꢀ
2
9
-1
30
-1
(nꢀCOOꢀbridged), ꢀ720ꢀcm ꢀ(orthometallation) ꢀandꢀ455ꢀcm ꢀ
11
31
industrialꢀ applications.ꢀ Variousꢀ supportsꢀ includingꢀ silica, ꢀ
(nꢀ Pd–N). ꢀ Theꢀ UV-Visꢀ spectraꢀ providedꢀ furtherꢀ evidenceꢀ
1
2
13
nanoporousꢀ carbon, ꢀ hydrotalcites, ꢀ zeolitesꢀ andꢀ zeolitesꢀ
forꢀ theꢀ presenceꢀ ofꢀ palladiumꢀ onꢀ theꢀ polymerꢀ support.ꢀTheꢀ
absorptionꢀ maximaꢀ aroundꢀ 280–320ꢀ nmꢀ mayꢀ beꢀ attributedꢀ
toꢀπ→π*ꢀtransitionꢀinꢀpolymerꢀandꢀphenylꢀmoietiesꢀandꢀtheꢀ
absorptionꢀatꢀhigherꢀrangeꢀ(370–440ꢀnm)ꢀisꢀdueꢀtoꢀπ→π*ꢀandꢀ
n→π*ꢀ transitionsꢀ ofꢀ theꢀ imineꢀ systemꢀ inꢀ conjugationꢀ withꢀ
theꢀ aromaticꢀ nuclei.ꢀ Comparableꢀ IRꢀ andꢀ UVꢀ signalsꢀ wereꢀ
alsoꢀ observedꢀ forꢀ theꢀ usedꢀ catalyst.ꢀ Theꢀ scanningꢀ electronꢀ
micrographsꢀofꢀaminoꢀpolystyreneꢀandꢀtheꢀsupportedꢀcatalystꢀ
clearlyꢀshowꢀtheꢀmorphologicalꢀchangeꢀwhichꢀoccurredꢀonꢀtheꢀ
surfaceꢀofꢀpolystyreneꢀafterꢀloadingꢀofꢀtheꢀmetal.ꢀTheꢀcatalystꢀ
isꢀ insolubleꢀ inꢀ allꢀ commonꢀ solventsꢀ andꢀ thermallyꢀ stableꢀ
upꢀtoꢀ250ꢀ°C.
14
15
materials, ꢀ andꢀ polymers ꢀ areꢀ usedꢀ toꢀ heterogeniseꢀ theꢀ
homogeneousꢀcatalyst.
Theꢀ mostꢀ readilyꢀ availableꢀ formꢀ ofꢀ supportedꢀ catalystꢀ
isꢀ palladiumꢀ onꢀ charcoal,ꢀ whichꢀ isꢀ widelyꢀ usedꢀ asꢀ aꢀ
heterogeneousꢀ catalystꢀ forꢀ theꢀ Suzukiꢀ couplingꢀ reaction.ꢀ
ItꢀisꢀseenꢀthatꢀPd/Cꢀcatalysesꢀtheꢀcross-couplingꢀofꢀactivatedꢀ
haloarenesꢀwithꢀphenylboronicꢀacidꢀinꢀaꢀDMA–H Oꢀ(20ꢀ:ꢀ1)ꢀ
2
16
mixture. ꢀHowever,ꢀreusabilityꢀofꢀtheꢀcatalystꢀwasꢀnotꢀtestedꢀ
forꢀ theseꢀ reactionsꢀ andꢀ aꢀ longꢀ reactionꢀ timeꢀ isꢀ required.ꢀ
PalladiumꢀcomplexꢀimpregnatedꢀontoꢀanꢀMCM-41ꢀmatrixꢀisꢀ
1
7
foundꢀ toꢀ beꢀ activeꢀ towardsꢀ theꢀ Suzukiꢀ couplingꢀ reaction. ꢀ
Inꢀthisꢀcaseꢀalso,ꢀlowꢀturnoverꢀnumbersꢀandꢀleachingꢀofꢀtheꢀ
palladiumꢀcomplexꢀareꢀtheꢀmajorꢀproblems.ꢀLeachingꢀofꢀtheꢀ
metalꢀintoꢀsolutionꢀandꢀreuseꢀofꢀtheꢀcatalystꢀareꢀtheꢀimportantꢀ
issuesꢀ inꢀ couplingꢀ reactionsꢀ especiallyꢀ whenꢀ theꢀ reactionsꢀ
occurꢀ underꢀ heterogeneousꢀ conditions.ꢀ Metalꢀ contaminationꢀ
isꢀ ofꢀ greatꢀ concernꢀ forꢀ foodꢀ andꢀ pharmaceuticalꢀ industries.ꢀ
Itꢀ isꢀ thereforeꢀ necessaryꢀ toꢀ designꢀ aꢀ trulyꢀ heterogeneousꢀ
catalystꢀthatꢀcanꢀbeꢀeasilyꢀrecoveredꢀandꢀreusedꢀwithꢀminimalꢀ
palladiumꢀleachingꢀintoꢀsolutionꢀandꢀthereforeꢀveryꢀeffectiveꢀ
inꢀtermsꢀofꢀpracticalꢀapplicationꢀandꢀoperationalꢀsafety.
Theꢀ Suzukiꢀ cross-couplingꢀ reactionꢀ isꢀ aꢀ convenientꢀ
methodꢀ forꢀ theꢀ C–Cꢀ bondꢀ formationꢀ betweenꢀ arylꢀ halidesꢀ
withꢀarylboronicꢀacidsꢀyieldingꢀbiarylꢀderivatives.ꢀToꢀtestꢀtheꢀ
applicabilityꢀ ofꢀ theꢀ polymerꢀ anchoredꢀ palladiumꢀ (II)ꢀ Schiffꢀ
baseꢀ complexꢀ catalyst,ꢀ weꢀ examinedꢀ theꢀ Suzukiꢀ reactionꢀ
betweenꢀvariousꢀarylꢀhalidesꢀandꢀphenylꢀboronicꢀacidꢀinꢀtheꢀ
presenceꢀofꢀvariousꢀsolventsꢀandꢀbases.ꢀInꢀorderꢀtoꢀoptimiseꢀ
theꢀreactionꢀconditions,ꢀtheꢀSuzukiꢀreactionꢀofꢀ4-bromoanisoleꢀ
(1.0ꢀmmol)ꢀandꢀphenylboronicꢀacidꢀ(1.2ꢀmmol)ꢀwithꢀ0.1ꢀmol%ꢀ
ofꢀ Pdꢀ catalystꢀ atꢀ 80ꢀ°Cꢀ wasꢀ studiedꢀ asꢀ theꢀ modelꢀ reaction.ꢀ
Theꢀ effectsꢀ ofꢀ differentꢀ solventsꢀ andꢀ basesꢀ onꢀ theꢀ catalyticꢀ
activityꢀofꢀtheꢀpalladiumꢀcomplexꢀareꢀsummarisedꢀinꢀTableꢀ1.ꢀ
Itꢀ wasꢀ foundꢀ thatꢀ theꢀ reactionsꢀ performedꢀ inꢀ aꢀ mixtureꢀ ofꢀ
waterꢀandꢀaꢀpolarꢀorganicꢀsolventꢀ(1ꢀ:ꢀ1)ꢀmediumꢀwithꢀK CO ꢀ
Itꢀ seemsꢀ thatꢀ palladiumꢀ complexesꢀ anchoredꢀ withꢀ inꢀ
polymerꢀmatrixꢀexhibitꢀexcellentꢀcatalyticꢀactivityꢀforꢀSuzukiꢀ
*
ꢀCorrespondent.ꢀE-mail:ꢀmanir65@rediffmail.com
2
3
PAPER:ꢀJC090760
JCR_12_2009 Book.indb 756
11/12/2009 15:36

JOURNALꢀOFꢀCHEMICALꢀRESEARCHꢀ2009ꢀ 757
H
C
O
H
P
N
P
NH2
Toluene, reflux
p-aminopolystyrene
Pd(OAc)2
AcOH
P
N
OAc
OAc
H
Pd
Pd
H
N
P
P =Polystyrene Framework
polymer anchored
palladium (II) Schiff base complex
Scheme 1ꢀ SynthesisꢀofꢀpolymerꢀanchoredꢀPdꢀ(II)ꢀcatalyst.
atꢀ80ꢀ°Cꢀshowedꢀtheꢀbestꢀperformanceꢀ(entryꢀ4).ꢀByꢀcontrast,ꢀ
basesꢀutilisedꢀshowedꢀthatꢀcarbonateꢀbasesꢀwereꢀmoreꢀsuitableꢀ
thanꢀotherꢀbases.ꢀTheꢀreactionꢀproceedsꢀinꢀhighꢀyieldꢀinꢀtheꢀ
presenceꢀ ofꢀ K CO asꢀ base.ꢀ Theꢀ useꢀ ofꢀ sodiumꢀ acetate,ꢀ
theꢀ catalyticꢀ performanceꢀ wasꢀ notꢀ acceptableꢀ whenꢀ aꢀ nonꢀ
polarꢀsolventꢀtolueneꢀwasꢀemployedꢀ(entryꢀ2).ꢀWeꢀalsoꢀstudiedꢀ
couplingꢀreactionꢀinꢀsoleꢀwater.ꢀTheꢀcatalystꢀwasꢀalsoꢀactiveꢀ
inꢀsoleꢀwaterꢀmediumꢀ(entryꢀ3)ꢀbutꢀtheꢀconversionꢀwasꢀlow.ꢀ
Sinceꢀtheꢀstartingꢀ4-bromoanisoleꢀhadꢀpoorꢀsolubilityꢀinꢀwater,ꢀ
theꢀ additionꢀ ofꢀ DMFꢀ wasꢀ helpfulꢀ toꢀ solveꢀ theseꢀ solubilityꢀ
problems,ꢀandꢀacceleratedꢀtheꢀreaction.ꢀItꢀwasꢀseenꢀthat,ꢀhighꢀ
temperatureꢀwasꢀrequiredꢀtoꢀreachꢀreasonableꢀreactionꢀspeedꢀ
andꢀ toꢀ obtainedꢀ highꢀ yieldsꢀ ofꢀ theꢀ couplingꢀ productꢀ andꢀ
catalyticꢀ efficiency.ꢀAtꢀ roomꢀ temperature,ꢀ noꢀ reactionꢀ takesꢀ
placeꢀ(entryꢀ5).ꢀWeꢀalsoꢀinvestigatedꢀtheꢀabilityꢀofꢀdifferentꢀ
basesꢀinꢀtheꢀcouplingꢀreaction.ꢀTheꢀcomparisonꢀofꢀinorganicꢀ
2
3ꢀ
potassiumꢀphosphateꢀorꢀtrialkylamineꢀasꢀbaseꢀinꢀtheꢀcouplingꢀ
reactionꢀresultedꢀlowꢀyieldsꢀofꢀbiarylꢀproductsꢀ(entriesꢀ9–11).
Theꢀ aboveꢀ optimisedꢀ conditionsꢀ couldꢀ beꢀ appliedꢀ toꢀ theꢀ
couplingꢀreactionsꢀbetweenꢀphenylboronicꢀacidꢀandꢀaꢀvarietyꢀ
ofꢀ arylꢀ halidesꢀ assistedꢀ byꢀ theꢀ polymer-anchoredꢀ palladiumꢀ
(II)ꢀcomplexꢀandꢀtheꢀresultsꢀareꢀshownꢀinꢀTableꢀ2.ꢀFromꢀtheꢀ
resultsꢀitꢀisꢀseenꢀthatꢀtheꢀelectronicꢀeffectꢀofꢀsubstituentsꢀinꢀ
theꢀarylꢀbromidesꢀandꢀarylꢀiodidesꢀhadꢀaꢀgreatꢀinfluenceꢀonꢀ
theꢀreaction.ꢀTheꢀelectron-deficientꢀsubstratesꢀaffordꢀexcellentꢀ
yieldsꢀofꢀcouplingꢀproductsꢀwhileꢀelectron-richꢀsubstratesꢀgiveꢀ
Table 1ꢀ Suzukiꢀcross-couplingꢀreactionꢀusingꢀpolymerꢀanchoredꢀSchiffꢀbaseꢀPdꢀ(II)ꢀcomplexꢀcatalystꢀatꢀvariousꢀbasesꢀandꢀsolvents
catalyst
MeO
Br +
B(OH)
2
MeO
Entryꢀ
Baseꢀ
K CO ꢀ
Solventꢀ
Temperature/°Cꢀ
Time/hꢀ
Yield/%
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
1ꢀ
2ꢀ
3ꢀ
4ꢀ
5ꢀ
6ꢀ
7ꢀ
8ꢀ
9ꢀ
DMFꢀ
80ꢀ
100ꢀ
90ꢀ
80ꢀ
25ꢀ
80ꢀ
80ꢀ
80ꢀ
80ꢀ
80ꢀ
80ꢀ
80ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
8ꢀ
92
2
3
K CO ꢀ
Tolueneꢀ
Waterꢀ
45
2
3
K CO ꢀ
72
2
3
K CO ꢀ
DMF–H Oꢀ
97
2
3
2
K CO ꢀ
DMF–H Oꢀ
Noꢀreaction
2
3
2
Na CO ꢀ
DMF–H Oꢀ
81
74
21
Trace
17
3
0
2
3
2
Cs CO ꢀ
DMF–H Oꢀ
2
3
2
NaOHꢀ
NaOAcꢀ
K PO ꢀ
DMF–H Oꢀ
2
DMF–H Oꢀ
2
ꢀ
10ꢀ
11ꢀ
12ꢀ
DMF–H Oꢀ
3
4
2
ꢀ
Et Nꢀ
DMF–H Oꢀ
3
2
ꢀ
Na HPO ꢀ
DMF–H Oꢀ
2
4
2
Reactionꢀconditions:ꢀarylꢀhalideꢀ(1.0ꢀmmol),ꢀphenylboronicꢀacidꢀ(1.2ꢀmmol),ꢀcatalystꢀ(0.1ꢀmol%ꢀPd),ꢀbaseꢀ(2.0ꢀmmol),ꢀDMF–H Oꢀ
2
(
1 ꢀ: ꢀ1 ,ꢀ6ꢀmL),ꢀ80ꢀ°C.
YieldꢀdeterminedꢀbyꢀGCꢀandꢀGCMSꢀanalysis.
PAPER:ꢀJC090760
JCR_12_2009 Book.indb 757
11/12/2009 15:36

7
58ꢀ JOURNALꢀOFꢀCHEMICALꢀRESEARCHꢀ2009
Table 2ꢀ Suzukiꢀ cross-couplingꢀ reactionꢀ ofꢀ arylꢀ halidesꢀ withꢀ phenylꢀ boronicꢀ acidꢀ withꢀ polymerꢀ anchoredꢀ Pdꢀ (II)ꢀ Schiffꢀ baseꢀ
complexꢀcatalyst
catalyst, K CO3
2
Br +
B(OH)
2
R
DMF-H O, 80°C
2
R
Entryꢀ
Substrateꢀ
Productꢀ
Time/hꢀ
Isolatedꢀyield/%
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
1ꢀ
2ꢀ
3ꢀ
4ꢀ
5ꢀ
6ꢀ
7ꢀ
8ꢀ
9ꢀ
Bromobenzeneꢀ
Biphenylꢀ
4.5ꢀ
4.5ꢀ
8ꢀ
96
99
78
97
99
90
97
98
91
99
86
84
98
98
92
99
99
91
81
Iodobenzeneꢀ
Biphenylꢀ
Chlorobenzeneꢀ
4-Bromoanisoleꢀ
3-Nitrobrobenzeneꢀ
4-Bromotolueneꢀ
4-Bromobenzaldehydeꢀ
4-Cyanobromobenzeneꢀ
4-Bromophenolꢀ
4-Bromoacetophenoneꢀ
2-Nitrobromobenzeneꢀ
2-Bromopyridineꢀ
4-Iodoanisoleꢀ
3-Nitroiodobenzeneꢀ
4-Iodotolueneꢀ
Biphenylꢀ
4-Methoxybiphenylꢀ
3-Nitrobiphenylꢀ
4-Methylbiphenylꢀ
4-Formylbiphenylꢀ
4-Cyanobiphenylꢀ
4-Hydroxybiphenylꢀ
4-Acetylbiphenylꢀ
2-Nitrobiphenylꢀ
2-Phenylpyridineꢀ
4-Methoxybiphenylꢀ
3-Nitrobiphenylꢀ
4-Methylbiphenylꢀ
4-Acetylbiphenylꢀ
4-Cyanobiphenylꢀ
4-Hydroxybiphenylꢀ
4-Acetylbiphenylꢀ
5ꢀ
5ꢀ
6ꢀ
6ꢀ
5ꢀ
6ꢀ
ꢀ
10ꢀ
11ꢀ
12ꢀ
13ꢀ
14ꢀ
15ꢀ
16ꢀ
17ꢀ
18ꢀ
19ꢀ
5ꢀ
ꢀ
8ꢀ
ꢀ
8ꢀ
ꢀ
5ꢀ
ꢀ
4.5ꢀ
4.5ꢀ
4ꢀ
ꢀ
ꢀ
4-Iodoacetophenoneꢀ
4-Cyanoiodobenzeneꢀ
4-Iodophenolꢀ
ꢀ
4ꢀ
ꢀ
5ꢀ
ꢀ
4-Chloroacetophenoneꢀ
8ꢀ
Reactionꢀconditions:ꢀarylꢀhalideꢀ(1.0ꢀmmol),ꢀphenylboronicꢀacidꢀ(1.2ꢀmmol),ꢀcatalystꢀ(0.1ꢀmol%ꢀPd),ꢀK CO ꢀ(2.0ꢀmmol),ꢀDMF–H Oꢀ
2
3
2
(
1:1,ꢀ6ꢀmL),ꢀ80ꢀ°C.
Isolatedꢀyieldsꢀwereꢀcalculatedꢀfromꢀtheꢀmassꢀofꢀtheꢀproductꢀafterꢀseparationꢀbyꢀcolumnꢀchromatography.ꢀAllꢀtheꢀisolatedꢀproductsꢀ
showedꢀmoreꢀthanꢀ99%ꢀofꢀGCꢀpurity.
moderateꢀyieldsꢀofꢀcoupledꢀproductꢀunderꢀtheꢀsameꢀreactionꢀ
conditions.ꢀ Non-activatedꢀ neutralꢀ substratesꢀ alsoꢀ giveꢀ goodꢀ
yieldsꢀcoupledꢀproducts.ꢀThisꢀisꢀconsistentꢀwithꢀtheꢀgeneralꢀ
behaviourꢀ observedꢀ forꢀ theꢀ palladium-catalysedꢀ Suzukiꢀ
presentꢀ polymer-anchoredꢀ catalystꢀ wasꢀ comparedꢀ toꢀ thatꢀ
ofꢀ theꢀ correspondingꢀ homogeneousꢀ analogueꢀ inꢀ theꢀ Suzukiꢀ
couplingꢀreaction.ꢀTheꢀresultsꢀshowedꢀthatꢀtheꢀhomogeneousꢀ
catalystꢀ isꢀ lessꢀ reactiveꢀ thanꢀ heterogeneousꢀ catalyst.ꢀ
Theꢀreactionꢀusingꢀhomogeneousꢀcatalystꢀwithꢀiodoꢀbenzeneꢀ
32
reactions. ꢀ Stericallyꢀ hinderedꢀ ortho-substitutedꢀ substrate,ꢀ
-bromonitroꢀ benzene,ꢀ wasꢀ alsoꢀ foundꢀ toꢀ reactꢀ smoothlyꢀ
2
andꢀphenylboronicꢀacidꢀinꢀDMF–H Oꢀmediumꢀatꢀ80ꢀ°Cꢀforꢀ8ꢀhꢀ
2
underꢀ theꢀ conditionꢀ givingꢀ aꢀ goodꢀ yieldꢀ ofꢀ theꢀ desiredꢀ
couplingꢀ productsꢀ (entryꢀ 11).ꢀ Anꢀ heteroarylꢀ bromide,ꢀ suchꢀ
asꢀ2-bromopyridine,ꢀcoupledꢀeffectivelyꢀwithꢀphenylboronicꢀ
acidꢀ providingꢀ 84%ꢀ ofꢀ theꢀ biarylꢀ productsꢀ (entryꢀ 12).ꢀ
Theꢀcatalystꢀisꢀcapableꢀofꢀactivatingꢀchlorobenzeneꢀ(entryꢀ3)ꢀ
whichꢀnormallyꢀremainsꢀunreactiveꢀinꢀSuzukiꢀcross-couplingꢀ
reactions.ꢀHowever,ꢀlessꢀreactiveꢀchlorobenzeneꢀgaveꢀpoorerꢀ
conversionꢀcomparedꢀtoꢀarylꢀbromidesꢀorꢀiodides.
resultsꢀinꢀ43%ꢀconversion,ꢀwhileꢀtheꢀanalogousꢀheterogeneousꢀ
reactionꢀ wasꢀ performedꢀ successfullyꢀ withꢀ 99%ꢀ conversionꢀ
byꢀGC.ꢀTheꢀactivityꢀofꢀtheꢀcatalystꢀwasꢀalsoꢀcomparedꢀwithꢀ
someꢀ otherꢀ heterogeneousꢀ catalystꢀ suchꢀ asꢀ Pd ꢀ sepiolite. ꢀ
Theꢀresultsꢀshowꢀthatꢀourꢀcatalystꢀisꢀsuperiorꢀtoꢀtheꢀreportedꢀ
catalystꢀinꢀtermsꢀofꢀreactionꢀtime,ꢀreactionꢀtemperatureꢀandꢀ
productꢀyield.
ForꢀtheꢀrecyclingꢀstudyꢀtheꢀSuzukiꢀcross-couplingꢀreactionꢀ
wasꢀperformedꢀwithꢀ4-bromoanisoleꢀandꢀphenylboronicꢀacidꢀ
maintainingꢀtheꢀsameꢀreactionꢀconditionsꢀusingꢀtheꢀrecoveredꢀ
catalyst.ꢀ Eachꢀ timeꢀ afterꢀ completionꢀ ofꢀ theꢀ reaction,ꢀ theꢀ
catalystꢀwasꢀrecoveredꢀbyꢀsimpleꢀfiltration,ꢀwashedꢀthoroughlyꢀ
2
+
33
Inꢀorderꢀtoꢀseeꢀtheꢀeffectꢀofꢀanchoring,ꢀtheꢀactivityꢀofꢀtheꢀ
100
withꢀ DMFꢀ andꢀ H Oꢀ toꢀ removeꢀ anyꢀ excessꢀ reagents,ꢀ driedꢀ
2
8
6
4
2
0
0
0
0
0
underꢀvacuumꢀandꢀreusedꢀunderꢀtheꢀsameꢀreactionꢀconditionsꢀ
asꢀforꢀtheꢀinitialꢀrunꢀwithoutꢀanyꢀregeneration.ꢀTheꢀrecyclingꢀ
efficiencyꢀofꢀtheꢀcatalystꢀupꢀtoꢀsevenꢀsuccessiveꢀrunsꢀisꢀshownꢀ
inꢀFig.ꢀ1.ꢀFromꢀtheꢀresults,ꢀitꢀisꢀseenꢀthatꢀtheꢀcatalystꢀretainedꢀ
itsꢀ highꢀ catalyticꢀ activityꢀ inꢀ theseꢀ sevenꢀ repeatedꢀ cycles.ꢀ
Moreoverꢀ atomicꢀ absorptionꢀ spectroscopyꢀ analysisꢀ ofꢀ theꢀ
filtrateꢀconfirmsꢀthatꢀthereꢀwasꢀnoꢀleachingꢀofꢀtheꢀmetalꢀfromꢀ
theꢀpolymerꢀanchoredꢀcatalystꢀ(<0.2ꢀppmꢀPdꢀconcentration).
Inꢀ summary,ꢀ weꢀ haveꢀ describedꢀ aꢀ simpleꢀ heterogeneousꢀ
palladiumꢀ catalyticꢀ systemꢀ forꢀ theꢀ Suzukiꢀ cross-couplingꢀ
reactionꢀ ofꢀ arylꢀ halides.ꢀ Thisꢀ polymerꢀ anchoredꢀ catalyst,ꢀ
P-[{(NCH)C H }Pd(OAc)] isꢀ easyꢀ toꢀ make,ꢀ air-stable,ꢀ
inexpensiveꢀ andꢀ non-pollutingꢀ solid.ꢀ Theꢀ remarkableꢀ
advantagesꢀ withꢀ theꢀ useꢀ ofꢀ theꢀ catalystꢀ areꢀ itsꢀ readyꢀ
accessibility,ꢀ itsꢀ reusabilityꢀ andꢀ storage.ꢀ Furthermore,ꢀ theꢀ
usedꢀ catalystꢀ isꢀ freeꢀ fromꢀ fireꢀ hazardsꢀ orꢀ explosions.ꢀ Theꢀ
catalystꢀhasꢀshownꢀaꢀnotableꢀactivityꢀtowardsꢀaꢀwideꢀvarietyꢀ
ofꢀsubstratesꢀandꢀexcellentꢀyieldsꢀofꢀproductsꢀareꢀobtainedꢀinꢀ
aqueousꢀmedia.ꢀTheꢀsubsequentꢀreuseꢀofꢀtheꢀcatalystꢀwithoutꢀ
6
4
2ꢀ
1st
3rd
5th
7th
Number of cycles
Fig. 1ꢀ Recyclingꢀ efficiencyꢀ forꢀ theꢀ couplingꢀ reactionꢀ ofꢀ
-bromoanisole
4
PAPER:ꢀJC090760
JCR_12_2009 Book.indb 758
11/12/2009 15:36

JOURNALꢀOFꢀCHEMICALꢀRESEARCHꢀ2009ꢀ 759
anyꢀlossꢀofꢀcatalyticꢀactivityꢀmakesꢀitꢀanꢀidealꢀprotocolꢀandꢀaꢀ
usefulꢀandꢀattractiveꢀalternativeꢀforꢀtheꢀsynthesisꢀofꢀbiaryls.ꢀ
Furtherꢀstudiesꢀofꢀotherꢀcouplingꢀreactionsꢀcatalysedꢀbyꢀthisꢀ
systemꢀareꢀcurrentlyꢀinꢀprogress.
progressꢀ ofꢀ theꢀ reactionꢀ samplesꢀ ofꢀ theꢀ reactionꢀ mixturesꢀ wereꢀ
collectedꢀ atꢀ differentꢀ timeꢀ intervalꢀ andꢀ quantifiedꢀ byꢀ GCꢀ analysis.ꢀ
Atꢀ theꢀ endꢀ ofꢀ theꢀ reaction,ꢀ theꢀ catalystꢀ wasꢀ separatedꢀ byꢀ simpleꢀ
filtration.ꢀTheꢀfiltrateꢀwasꢀextractedꢀwithꢀEt Oꢀandꢀpassedꢀthroughꢀaꢀ
2
padꢀofꢀsilicaꢀgel.ꢀTheꢀorganicꢀphaseꢀthusꢀcollectedꢀwasꢀdriedꢀoverꢀ
Na SO ,ꢀfiltered,ꢀconcentratedꢀandꢀtheꢀresidueꢀwasꢀpurifiedꢀbyꢀflashꢀ
2
4
Experimental
Materials and instrument
Analyticalꢀ gradeꢀ reagentsꢀ andꢀ freshlyꢀ distilledꢀ solventsꢀ wereꢀ usedꢀ
throughoutꢀ theꢀ investigation.ꢀ Poly(styrene-co-divinylꢀ benzene)ꢀ
chromatographyꢀonꢀsilicaꢀgel.ꢀTheꢀproductꢀwasꢀanalysedꢀbyꢀGC-MS.
38
39
1
Biphenyl: Whiteꢀ solid,ꢀ m.p.ꢀ 69 ꢀ° Cꢀ (lit. ꢀ 69–70 ꢀ° C).ꢀ Hꢀ NMRꢀ
13
(
300ꢀMHz,ꢀCDCl )ꢀd:ꢀ7.58–7.28ꢀ(m,ꢀ10H);ꢀ CꢀNMRꢀ(75ꢀMHz,ꢀCDCl )ꢀ
3 3
-1
d:ꢀ 141.2,ꢀ 128.7,ꢀ 127.2,ꢀ 127.1;ꢀ IRꢀ (cm ,ꢀ KBr)ꢀ n:ꢀ 2682,ꢀ 1630,ꢀ 1600,ꢀ
1
474,ꢀ1350.ꢀGC-MS:ꢀm/zꢀ154.
2
%ꢀ crosslinked,ꢀ (Art.No.ꢀ 434442-50G)ꢀ wasꢀ suppliedꢀ byꢀ Aldrich,ꢀ
3
8
40
1
4
-Methoxybiphenyl: ꢀWhiteꢀsolid, m.p.ꢀ85ꢀ°Cꢀ(lit. ꢀ86ꢀ°C).ꢀ HꢀNMRꢀ
USAꢀ andꢀ palladiumꢀ acetateꢀ wasꢀ purchasedꢀ fromꢀ Aroraꢀ Matthey.ꢀ
OtherꢀorganicꢀreagentsꢀwereꢀpurchasedꢀfromꢀMerckꢀandꢀwereꢀusedꢀasꢀ
suchꢀwithoutꢀfurtherꢀpurification.
(
3
1
300ꢀMHz,CDCl )ꢀd:ꢀ7.52–7.24ꢀ(m,ꢀ7H),ꢀ6.96–6.90ꢀ(m,ꢀ2H),ꢀ3.77ꢀ(s,ꢀ
3
1
3
H);ꢀ CꢀNMR(75ꢀMHz,ꢀCDCl )ꢀd:ꢀ159.1,ꢀ140.7,ꢀ133.7,ꢀ128.7,ꢀ128.1,ꢀ
3
-1
26.6,ꢀ126.6,ꢀ114.2,ꢀ55.2;ꢀIRꢀ(cm ,ꢀKBr)ꢀn:ꢀ2832,ꢀ1632,ꢀ1523,ꢀ1486,ꢀ
Theꢀ FTIRꢀ spectraꢀ ofꢀ theꢀ samplesꢀ wereꢀ recordedꢀ fromꢀ 400ꢀ toꢀ
-1
1350.ꢀGC-MS:ꢀm/zꢀ184.
4
000ꢀ cm ꢀ onꢀ aꢀ Perkin-Elmerꢀ FTIRꢀ 783ꢀ spectrophotometerꢀ usingꢀ
KBrꢀ pellets.ꢀ UV-Visꢀ spectraꢀ wereꢀ takenꢀ usingꢀ aꢀ Shimadzuꢀ UV-
401PCꢀ doubledꢀ beamꢀ spectrophotometerꢀ havingꢀ anꢀ integratingꢀ
sphereꢀ attachmentꢀ forꢀ solidꢀ samples.ꢀ Thermogravimetricꢀ analysisꢀ
TGA)ꢀ wasꢀ carriedꢀ outꢀ usingꢀ aꢀ Mettlerꢀ Toledoꢀ TGA/DTAꢀ 851e.ꢀ
3
8
41
1
3
-Nitrobiphenyl: ꢀYellowꢀsolid,ꢀm.p.ꢀ60ꢀ°Cꢀ(lit. ꢀ59ꢀ°C).ꢀ HꢀNMRꢀ
(
300ꢀMHz,ꢀCDCl )ꢀd:ꢀ8.42ꢀ(dd,ꢀ1H,ꢀJ = 2.4,ꢀ1.8ꢀHz),ꢀ8.14ꢀ(dd,ꢀ1H,ꢀ
3
2
J = 8.1,ꢀ2.4ꢀHz),7.86ꢀ(d,ꢀ1H,ꢀJ = 7.8ꢀHz),ꢀ7.54ꢀ(dd,ꢀ3H,ꢀJ = 8.7,ꢀ8.1ꢀHz),ꢀ
7
1
1
3
.49–7.34(m,ꢀ 3H);ꢀ Cꢀ NMRꢀ (75ꢀ MHz,ꢀ CDCl )ꢀ d:ꢀ 148.7,ꢀ 142.9,ꢀ
3
-1
(
38.6,ꢀ133.0,ꢀ129.7,129.1,ꢀ128.5,ꢀ127.1,ꢀ122.0,ꢀ121.9;ꢀIRꢀ(cm ,ꢀKBr)ꢀ
Surfaceꢀ morphologyꢀ ofꢀ theꢀ samplesꢀ wasꢀ measuredꢀ usingꢀ aꢀ
scanningꢀ electronꢀ microscopeꢀ (SEM)ꢀ (ZEISSꢀ EVO40,ꢀ England)ꢀ
equippedꢀ withꢀ EDXꢀ facility.ꢀ Palladiumꢀ contentꢀ inꢀ theꢀ catalystꢀ
wasꢀ determinedꢀ usingꢀ aꢀ Varianꢀ AA240ꢀ atomicꢀ absorptionꢀ
spectrophotometerꢀ(AAS).
n:ꢀ2675,ꢀ1601,ꢀ1523,1457,ꢀ1345,ꢀ1106.ꢀGC-MS:ꢀm/zꢀ199.
CAUTION:ꢀTheꢀisomerꢀ4-nitrobiphenylꢀisꢀaꢀknownꢀcarcinogen.
38
42
4
-Methylbiphenyl: ꢀ Whiteꢀ solid,ꢀ m.p.ꢀ 46–47 ꢀ° Cꢀ (lit. ꢀ 44–46 ꢀ° C).ꢀ
1
13
HꢀNMRꢀ(300ꢀMHz,ꢀCDCl )ꢀd:ꢀ7.58–7.23ꢀ(m,ꢀ9H),ꢀ2.37ꢀ(s,ꢀ3H);ꢀ Cꢀ
3
Synthesis of the metal complex
Preparation of p-aminopolystyrene
NMRꢀ(75ꢀMHz,ꢀCDCl )ꢀd:ꢀ141.2,ꢀ138.4,ꢀ137.0,ꢀ129.5,ꢀ128.7,ꢀ127.0,ꢀ
3
-1
2
0.1;ꢀIRꢀ(cm ,ꢀKBr)ꢀn:ꢀ2793,ꢀ2662,ꢀ1631,ꢀ1351.ꢀGC-MS:ꢀm/zꢀ168.
43
1
4
-Formylbiphenyl: ꢀColourlessꢀliquid,ꢀ HꢀNMRꢀ(300ꢀMHz,ꢀCDCl ):ꢀ
3
CAUTION:ꢀMixturesꢀofꢀfumingꢀnitricꢀacidꢀandꢀaceticꢀanhydrideꢀ
d:ꢀ7.41–7.53ꢀ(m,ꢀ3H),ꢀ7.62–7.67ꢀ(m,ꢀ2H),ꢀ7.74–7.77ꢀ(m,ꢀ2H),ꢀ7.94–7.97ꢀ
3
4
areꢀknownꢀtoꢀbeꢀdangerouslyꢀunstableꢀandꢀcanꢀdetonate, ꢀseeꢀalsoꢀ
refsꢀ35ꢀandꢀ36.ꢀAlthoughꢀinꢀtheꢀpresentꢀcase,ꢀtheꢀacidꢀusedꢀinꢀnotꢀ
fumingꢀbutꢀcautionꢀisꢀadvised.
13
(
1
m,ꢀ2H),ꢀ10.06ꢀ(s,ꢀ1H);ꢀ CꢀNMRꢀ(75ꢀMHz,ꢀCDCl )d:ꢀ127.3,ꢀ127.6,ꢀ
3
28.4,ꢀ129.0,ꢀ130.2,ꢀ135.2,ꢀ139.7,ꢀ147.2,ꢀ191.9;ꢀGC-MS:ꢀm/zꢀ182.
-Cyanobiphenyl: ꢀWhiteꢀsolid,ꢀm.p.ꢀ83–85ꢀ°Cꢀ(lit. ꢀ84–86ꢀ°C).ꢀ
38
41
4
1
Hꢀ NMRꢀ (300ꢀ MHz,CDCl )ꢀ d:ꢀ 7.75–7.64ꢀ (m,ꢀ 4H),ꢀ 7.60–7.55ꢀ (m,ꢀ
3
Theꢀ suspensionꢀ ofꢀ macroporousꢀ polystyreneꢀ beadsꢀ (5.0ꢀ g)ꢀ inꢀ aꢀ
mixtureꢀofꢀaceticꢀanhydrideꢀ(20ꢀmL),ꢀnitricꢀacidꢀ(~70%,ꢀ2ꢀmL)ꢀandꢀ
glacialꢀaceticꢀacidꢀ(4ꢀmL)ꢀwasꢀconstantlyꢀstirredꢀforꢀ30ꢀminꢀatꢀ5ꢀ°Cꢀ
andꢀforꢀ 5ꢀ hꢀ atꢀ50ꢀ°C. ꢀTheꢀ correspondingꢀp-nitroꢀ polystyreneꢀwasꢀ
washedꢀsuccessivelyꢀwithꢀaceticꢀacid,ꢀwaterꢀandꢀmethanolꢀandꢀfinallyꢀ
driedꢀ underꢀ vacuum.ꢀ Chemicalꢀ analysisꢀ ofꢀ P–NO ꢀ (Pꢀ =ꢀ polymerꢀ
moiety)ꢀsuggestsꢀthatꢀ56%ꢀnitrationꢀofꢀtheꢀpolystyreneꢀring.
1
3
2
1
H),ꢀ 7.50–7.41ꢀ (m,ꢀ 3H);ꢀ Cꢀ NMRꢀ (75ꢀ MHz,ꢀ CDCl )ꢀ d:ꢀ 145.6,ꢀ
3
-1
39.1,ꢀ132.5,ꢀ129.0,ꢀ128.6,ꢀ127.6,ꢀ127.4,118.9,ꢀ110.8;ꢀIRꢀ(cm ,ꢀKBr)ꢀ
n:ꢀ2661,ꢀ2227,ꢀ1605,ꢀ1485,ꢀ768.ꢀGC-MS:ꢀm/zꢀ179.
3
7
44
44
4
-Hydroxybiphenyl: ꢀ Colourlessꢀ solid,ꢀ m.p.ꢀ 165 ꢀ° Cꢀ (lit. ꢀ 166 ꢀ° C).ꢀ
1
Hꢀ NMRꢀ (acetone-d ):ꢀ =ꢀ 8.44(s,1H,OH),ꢀ 7.57ꢀ (d,ꢀ J = 7.3ꢀ Hz,ꢀ 2H,ꢀ
6
Hꢀ
2
ArH),ꢀ7.50ꢀ(d,ꢀJ = 8.6ꢀHz,ꢀ2H,ꢀArH),ꢀ7.42-7.37ꢀ(m,ꢀ2H,ꢀArH),ꢀ7.29–7.24ꢀ
13
(
m,ꢀ1H,ꢀArH)ꢀandꢀ6.93ꢀ(d,ꢀJ = 8.6ꢀHz,ꢀ2H,ꢀArH);ꢀ CꢀNMRꢀ(acetone-d6):ꢀ
Aꢀ mixtureꢀ ofꢀ aceticꢀ acidꢀ (20ꢀ mL),ꢀ stannousꢀ chlorideꢀ (5ꢀ g),ꢀ
concentratedꢀ hydrochloricꢀ acidꢀ (6ꢀ mL)ꢀ andꢀ theꢀ suspensionꢀ ofꢀ
p-nitropolystyreneꢀ(5.0ꢀg)ꢀwereꢀstirredꢀforꢀ72ꢀhꢀatꢀroomꢀtemperatureꢀ
toꢀ reduceꢀ theꢀ nitro-compoundꢀ toꢀ theꢀ correspondingꢀ amineꢀ
hydrochloride [34].ꢀ Theꢀ residueꢀ wasꢀ washedꢀ severalꢀ timesꢀ withꢀ
hydrochloricꢀacidꢀ(12ꢀM)ꢀandꢀglacialꢀaceticꢀacidꢀ(1:4)ꢀmixtureꢀandꢀ
thenꢀwithꢀmethanol.ꢀTheꢀestimationꢀofꢀchlorideꢀandꢀnitrogenꢀinꢀtheꢀ
polymerꢀamineꢀhydrochlorideꢀsuggestsꢀapproximatelyꢀ90%ꢀreductionꢀ
ofꢀ nitropolystyrene.ꢀTheꢀ productꢀ onꢀ repeatedꢀ treatmentꢀ withꢀ diluteꢀ
alcoholicꢀ NaOHꢀ (5%)ꢀ producedꢀ theꢀ correspondingꢀ freeꢀ amine.ꢀ
Thisꢀwasꢀwashedꢀwithꢀalcoholꢀandꢀdriedꢀunderꢀvacuum.
Cꢀ=ꢀ158.0,ꢀ141.8,ꢀ133.1ꢀ(ArC),ꢀ129.5,ꢀ128.8,ꢀ127.2,ꢀ127.1ꢀandꢀ116.5ꢀ
-1
(
ArCH).ꢀIRꢀ(cm ,ꢀKBr)ꢀn:ꢀ3404,ꢀ1610,ꢀ1523.GC-MS:ꢀm/zꢀ170.
38
45
4
-Acetylbiphenyl: ꢀWhiteꢀsolid,ꢀm.p.ꢀ118–119 ꢀ° Cꢀ(lit ꢀ119–120 ꢀ° C).ꢀ
1
HꢀNMRꢀ(300ꢀMHz,ꢀCDCl )ꢀd:ꢀ8.05ꢀ(d,ꢀ2H,ꢀJ = 8.4ꢀHz),ꢀ7.72–7.60ꢀ
3
1
3
(m,ꢀ4H),ꢀ7.50–7.40(m,ꢀ3H),ꢀ2.64ꢀ(s,ꢀ3H);ꢀ CꢀNMRꢀ(75ꢀMHz,ꢀCDCl )ꢀ
3
d:ꢀ197.5,ꢀ145.7,ꢀ139.8,ꢀ135.9,ꢀ128.9,ꢀ128.8,ꢀ128.2,ꢀ127.2,ꢀ127.1,ꢀ26.5;ꢀ
-1
IRꢀ(cm ,ꢀKBr)ꢀn:ꢀ2999,ꢀ2789,ꢀ2660,ꢀ1679,ꢀ1604,ꢀ1501,ꢀ1351,ꢀ764.ꢀ
GC-MS:ꢀm/zꢀ196.
4
6
1
2
-Nitrobiphenyl: ꢀPaleꢀyellowꢀoil,ꢀ HꢀNMRꢀ(400ꢀMHz,ꢀCDCl ):ꢀ
3
dꢀ7.86ꢀ(d,ꢀJ = 8ꢀHz,ꢀ1H),ꢀ7.62ꢀ(t,ꢀJ = 7.2ꢀHz,ꢀ1H),ꢀ7.51–7.40ꢀ(m,ꢀ5H),ꢀ
1
3
7
1
.33–7.30ꢀ(m,ꢀ2H);ꢀ CꢀNMRꢀ(100ꢀMHz,ꢀCDCl )ꢀd:ꢀ163.7,ꢀ140.3,ꢀ
3
37.3,ꢀ128.8,ꢀ128.7,ꢀ128.6,ꢀ127.3,ꢀ127.0,ꢀ115.7,ꢀ115.5.
Preparation of polymer anchored Schiff base ligand and palladium
47
1
2
-Phenylpyridine: ꢀColourlessꢀliquid.ꢀ HꢀNMRꢀ(CDCl ,ꢀ200ꢀMHz)ꢀ
3
(
II) complex
dꢀ8.62ꢀ(d,ꢀ1ꢀH),ꢀ7.98ꢀ(d,ꢀ2ꢀH),ꢀ7.65ꢀ(d,ꢀ1ꢀH),ꢀ7.64ꢀ(dd,ꢀ1ꢀH),ꢀ7.44ꢀ(dd,ꢀ
Theꢀ suspensionꢀ ofꢀ macroporousꢀ pꢀ aminopolystyreneꢀ (2ꢀ g)ꢀ inꢀ dryꢀ
13
2
ꢀ H),ꢀ 7.38ꢀ (dd,ꢀ 1ꢀ H),ꢀ 7.14ꢀ (dd,1H).ꢀ Cꢀ NMRꢀ (CDCl ,50ꢀ MHz)ꢀ
3
tolueneꢀ(30ꢀmL)ꢀwasꢀtakenꢀinꢀaꢀroundꢀbottomꢀflask.ꢀBenzaldehydeꢀ
dꢀ 157.3,ꢀ 149.6,ꢀ 139.3,ꢀ 136.6,ꢀ 128.9,ꢀ 128.7,ꢀ 126.8,122.0,ꢀ 120.3.ꢀ
GC-MS:ꢀm/zꢀ155.
(5ꢀmL)ꢀwasꢀaddedꢀdropwiseꢀtoꢀtheꢀstirringꢀsuspension.ꢀTheꢀreactionꢀ
mixtureꢀ wasꢀ refluxedꢀ forꢀ 72ꢀ hꢀ untilꢀ theꢀ colourꢀ ofꢀ theꢀ suspensionꢀ
changedꢀ toꢀ yellow.ꢀ Afterꢀ coolingꢀ toꢀ roomꢀ temperature,ꢀ theꢀ lightꢀ
yellowꢀpolymer-anchoredꢀSchiffꢀbaseꢀligandꢀwasꢀfilteredꢀoff,ꢀwashedꢀ
successivelyꢀwithꢀtoluene,ꢀtetrahydrofuranꢀandꢀmethanolꢀandꢀfinallyꢀ
driedꢀatꢀreducedꢀpressure.ꢀTheꢀchemicalꢀanalysisꢀsuggestsꢀthatꢀnearlyꢀ
Weꢀ gratefullyꢀ acknowledgeꢀ Departmentꢀ ofꢀ Scienceꢀ andꢀ
Technologyꢀ (DST),ꢀ Councilꢀ ofꢀ Scientificꢀ andꢀ Industrialꢀ
Researchꢀ(CSIR)ꢀandꢀUniversityꢀGrantꢀCommissionꢀ(UGC),ꢀ
Newꢀ Delhi,ꢀ Indiaꢀ forꢀ funding.ꢀWeꢀ alsoꢀ thankꢀ theꢀ DSTꢀ andꢀ
UGC,ꢀ Newꢀ Delhi,ꢀ Indiaꢀ forꢀ providingꢀ instrumentalꢀ supportꢀ
underꢀtheꢀFISTꢀandꢀSAPꢀprogrammes.
8
0%ꢀofꢀtheꢀpolymerꢀamineꢀgroupsꢀreactꢀwithꢀtheꢀcarbonylꢀcompoundꢀ
toꢀproduceꢀtheꢀcorrespondingꢀSchiffꢀbaseꢀligand.
Theꢀsuspensionꢀofꢀtheꢀpolymer-anchoredꢀSchiffꢀbaseꢀligandꢀ(2ꢀg)ꢀ
inꢀ aceticꢀ acidꢀ solutionꢀ (15ꢀ mL)ꢀ ofꢀ palladiumꢀ acetateꢀ (0.75ꢀ g)ꢀ wasꢀ
refluxedꢀonꢀanꢀoilꢀbathꢀforꢀ8ꢀhꢀwhenꢀtheꢀcolourꢀofꢀtheꢀsuspensionꢀ
changedꢀcompletelyꢀfromꢀyellowꢀtoꢀdeepꢀbrown.ꢀAfterꢀcoolingꢀtheꢀ
reactionꢀmixtureꢀtoꢀroomꢀtemperature,ꢀtheꢀseparatedꢀpolymerꢀcomplexꢀ
wasꢀ filteredꢀ out,ꢀ washedꢀ thoroughlyꢀ withꢀ tetrahydrofuranꢀ andꢀ
methanolꢀ andꢀ driedꢀ inꢀ roomꢀ temperatureꢀ underꢀ vacuum.ꢀ Chemicalꢀ
analysisꢀsuggestsꢀtheꢀcoordinationꢀofꢀnearlyꢀ50%ꢀofꢀtheꢀSchiffꢀbaseꢀtoꢀ
formꢀpalladiumꢀcomplex.
Received 27 August 2009; accepted 22 November 2009
Paper 09/0760 doi: 10.3184/030823409X12594170566203
Published online: 8 December 2009
References
ꢀ
ꢀ
ꢀ
ꢀ
1ꢀ N.ꢀMiyauraꢀandꢀA.ꢀSuzuki,ꢀChem. Rev.,ꢀ1995,ꢀ95,ꢀ2457.
2ꢀ A.ꢀSuzuki,ꢀJ. Organomet. Chem.,1999,ꢀ576,ꢀ147.
3ꢀ F.ꢀBellina,ꢀA.ꢀCarpitaꢀandꢀR.ꢀRossi,ꢀSynthesis,ꢀ2004,ꢀ15,ꢀ2419.
4ꢀ S.A.ꢀ Patil,ꢀ C.M.ꢀ Weng,ꢀ P.ꢀ Huangꢀ andꢀ F.ꢀ Hong,ꢀ Tetrahrdron,ꢀ 2009,ꢀ
65,ꢀ2889.
General procedure for the synthesis of biaryls
Aꢀmixtureꢀofꢀarylꢀhalideꢀ(1.0ꢀmmol),ꢀphenylboronicꢀacidꢀ(1.2ꢀmmol),ꢀ
K CO ꢀ(2.0ꢀmmol),ꢀDMF–H Oꢀ(3ꢀmL-3ꢀmL)ꢀandꢀcatalystꢀcontainingꢀ
2
3
2
0
.1ꢀ mol%ꢀ palladiumꢀ wasꢀ stirredꢀ atꢀ 80ꢀ°Cꢀ underꢀ air.ꢀ Toꢀ studyꢀ theꢀ
ꢀ 5ꢀ T.E.ꢀBarder,ꢀJ. Am. Chem. Soc.,ꢀ2006,ꢀ128,ꢀ898.
PAPER:ꢀJC090760
JCR_12_2009 Book.indb 759
11/12/2009 15:36

7
60ꢀ JOURNALꢀOFꢀCHEMICALꢀRESEARCHꢀ2009
ꢀ
ꢀ
6ꢀ S.D.ꢀ Walker,ꢀ T.E.ꢀ Barder,ꢀ J.R.ꢀ Martinelliꢀ andꢀ S.L.ꢀ Buchwald,ꢀ Angew.
Chem., Int. Ed.ꢀ2004,ꢀ43,ꢀ1871.
7ꢀ W.A.ꢀ Herrmann,ꢀ K.ꢀ Ofele,ꢀ D.ꢀ vonꢀ Preysingꢀ andꢀ S.K.ꢀ Schneider,ꢀ
J. Organomet. Chem.,ꢀ2003,ꢀ687,ꢀ229.
8ꢀ S.-Y.ꢀLiu,ꢀM.J.ꢀChoi,ꢀG.C.ꢀFu,ꢀChem. Commun.,ꢀ2001,ꢀ23,ꢀ2408.
9ꢀ J.W.ꢀByunꢀandꢀY.S.ꢀLee,ꢀTetrahedron Lett.,ꢀ2004,ꢀ45,ꢀ1837.
ꢀ27ꢀ K.ꢀInada,ꢀN.ꢀMiyaura.ꢀTetrahedron, 2000,ꢀ56,ꢀ8661.
ꢀ28ꢀ Y.ꢀUozumiꢀandꢀY.ꢀNakai,ꢀOrg. Lett.,ꢀ2002,ꢀ4,ꢀ2997.
ꢀ29ꢀ P.A.ꢀStephensonꢀandꢀG.ꢀWilkinson,ꢀInorg. Nucl. Chem.,1967,ꢀ29,ꢀ2122.
ꢀ
ꢀ
30ꢀ H.ꢀOnueꢀandꢀI.ꢀMoritani,ꢀJ. Organomet. Chem.,ꢀ1972,ꢀ43,ꢀ431.
31ꢀ J.R.ꢀDurig,ꢀR.ꢀLayton,ꢀD.W.ꢀSinkꢀandꢀB.R.ꢀMitchell,ꢀSpectrochim. Acta,ꢀ
965,ꢀ21,ꢀ1367.
32ꢀ R.S.ꢀVermaꢀandꢀK.P.ꢀNaicker,ꢀTetrahedron Lett.,ꢀ1999,ꢀ40,ꢀ439.
33ꢀ K.ꢀ Shimizu,ꢀ T.ꢀ Kan-no,ꢀ T.ꢀ Kodama,ꢀ H.ꢀ Hagiwaraꢀ andꢀ Y.ꢀ Kitayama,ꢀ
Tetrahedron Lett.,ꢀ2002,ꢀ43,ꢀ5653.
34ꢀ P.G.ꢀ Urbanꢀ (ed.)ꢀ Bretherick's Handbook of reactive chemical hazards,ꢀ
ꢀ
ꢀ
1
ꢀ
ꢀ
ꢀ
10ꢀ E.B.ꢀMubofu,ꢀJ.H.ꢀClarkꢀandꢀD.J.ꢀMacquarrie,ꢀGreen Chem.,ꢀ2001,ꢀ1,ꢀ23.
11ꢀ J.H.ꢀClark,ꢀD.J.ꢀMacQuarrieꢀandꢀE.B.ꢀMubofu,ꢀGreen Chem.,ꢀ2000,ꢀ2,ꢀ53.
12ꢀ A.N.ꢀVasiliev,ꢀL.V.ꢀGolovko,ꢀV.A.ꢀPovazhny,ꢀE.ꢀZlotnikov,ꢀJ.ꢀChenꢀandꢀ
J.G.ꢀKhinast,ꢀMicroporous Mesoporous Mater.,ꢀ2007,ꢀ101,ꢀ342.ꢀ
13ꢀ M.ꢀMora,ꢀC.J.ꢀSanchidrianꢀandꢀJ.R.ꢀRuiz,ꢀJ. Colloid Interface Sci.,ꢀ2006,ꢀ
02,ꢀ568.
14ꢀ L.ꢀArtokꢀandꢀH.ꢀBulut,ꢀTetrahedron Lett.,ꢀ2004,ꢀ45,ꢀ3881.
15ꢀ J.W.ꢀ Kim,ꢀ J.H.ꢀ Kim,ꢀ D.H.ꢀ Leeꢀ andꢀY.S.ꢀ Lee,ꢀ Tetrahedron Lett.,ꢀ 2006,ꢀ
7,ꢀ4745.
16ꢀ C.R.ꢀ LeBlond,ꢀ A.T.ꢀ Andrews,ꢀ Y.ꢀ Sunꢀ andꢀ R.ꢀ Sowa,ꢀ Org. Lett.,ꢀ 2001,ꢀ
,ꢀ1555.
17ꢀ H.ꢀ Kosslick,ꢀ I.ꢀ Monnich,ꢀ E.ꢀ Fuhrmann,ꢀ R.ꢀ Fricke,ꢀ D.ꢀ Mullerꢀ andꢀ
G.ꢀOehme,ꢀMicroporous Mesoporous Mater.,ꢀ2001,ꢀ537,ꢀ44.
18ꢀ T.Y.ꢀZhangꢀandꢀM.J.ꢀAllen,ꢀTetrahedron Lett.,ꢀ1999,ꢀ40,ꢀ5813.
19ꢀ J.H.ꢀLi,ꢀX.-C.ꢀHu,ꢀY.-X.ꢀXie,ꢀTetrahedron Lett., 2006,ꢀ47,ꢀ9239.
20ꢀ N.T.S.ꢀ Phan,ꢀ D.H.ꢀ Brownꢀ andꢀ P.ꢀ Styring,ꢀ Tetrahedron Lett.,ꢀ 2004,ꢀ
5,ꢀ7915.
21ꢀ J.-H.ꢀKim,ꢀJ.-W.ꢀKim,ꢀM.ꢀShokouhimehr,ꢀandꢀY.-S.ꢀLee,ꢀJ. Org. Chem.,ꢀ
005,ꢀ70,ꢀ6714.
22ꢀ B.ꢀKarimiꢀandꢀP.ꢀF.ꢀAkhavan,ꢀChem. Commun.,ꢀ2009,ꢀ25,ꢀ3750.
23ꢀ X.ꢀ Zeng,ꢀT.ꢀ Zhang,ꢀY.ꢀ Qin,ꢀ Z.ꢀWeiꢀ andꢀ M.ꢀ Luo,ꢀ Dalton Trans.,ꢀ 2009,ꢀ
9,ꢀ8341.
24ꢀ N.ꢀJamwal,ꢀM.ꢀGuptaꢀandꢀS.ꢀPaul,ꢀGreen Chem.,ꢀ2008,ꢀ9,ꢀ999.
25ꢀ N.T.S.ꢀPhan,ꢀJ.ꢀKhanꢀandꢀP.ꢀStyring,ꢀTetrahedron, 2005,ꢀ61,ꢀ12065.
26ꢀ P.G.ꢀSteelꢀandꢀC.W.T.ꢀTeasdale,ꢀTetrahedron Lett.,ꢀ2004,ꢀ45,ꢀ8977.
ꢀ
ꢀ
ꢀ
ꢀ
th
6
ꢀedn,ꢀButterworth,ꢀOxford,ꢀ1999,ꢀVol.1,ꢀpꢀ1568.
3
ꢀ35ꢀ G.A.ꢀOlah,ꢀChem. Br.,ꢀ1963,ꢀ32,ꢀ21.
ꢀ
ꢀ
ꢀ36ꢀ T.A.ꢀBrownꢀandꢀJ.A.C.ꢀWatt,ꢀChem. Br.,ꢀ1967,ꢀ3,ꢀ504.
ꢀ37ꢀ R.B.ꢀKing,ꢀE.M.ꢀSweet,ꢀJ. Org. Chem.,ꢀ1979,ꢀ44,ꢀ385.
ꢀ38ꢀ L.ꢀZhang,ꢀL.ꢀWang,ꢀH.ꢀLiꢀandꢀP.ꢀLi,ꢀSynthetic Commun.,ꢀ2008,ꢀ38,ꢀ1498.
ꢀ39ꢀ J.B.ꢀHendricksonꢀandꢀW.A.ꢀWolf,ꢀJ. Org. Chem.,ꢀ1968,ꢀ33,ꢀ3610.
ꢀ40ꢀ T.B.ꢀ Patrick,ꢀ R.P.ꢀ Willaredtꢀ andꢀ D.J.ꢀ DeGonia,ꢀ J. Org. Chem.,ꢀ 1985,ꢀ
4
ꢀ
3
ꢀ
5
0,ꢀ2232.
41ꢀ M.L.ꢀ Kantam,ꢀ M.ꢀ Roy,ꢀ S.ꢀ Roy,ꢀ B.ꢀ Sreedhar,ꢀ S.S.ꢀ Madhavendra,ꢀ
B.M.ꢀChoudaryꢀandꢀR.L.ꢀDey,ꢀTetrahedron,ꢀ2007,ꢀ63,ꢀ8002.
42ꢀ M.S.ꢀNewmanꢀandꢀJ.A.ꢀEberwein,ꢀJ. Org. Chem.,ꢀ1964,ꢀ29,ꢀ2516.
43ꢀ Z.ꢀXiong,ꢀN.ꢀWang,ꢀM.ꢀDai,ꢀA.ꢀLi,ꢀJ.ꢀChenꢀandꢀZ.ꢀYang,ꢀOrg. Lett.,ꢀ2004,ꢀ
9,ꢀ3337.
44ꢀ C.ꢀNajera,ꢀJ.ꢀGil-Molto,ꢀS.ꢀKarlstromꢀandꢀL.R.ꢀFalvello,ꢀOrg. Lett.,ꢀ2003,ꢀ
,ꢀ1451.
45ꢀ L.ꢀZhu,ꢀJ.ꢀDuquetteꢀandꢀM.ꢀZhang,ꢀJ. Org. Chem.,ꢀ2003,ꢀ68,ꢀ3729.
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
4
ꢀ
1
2
ꢀ
ꢀ
ꢀ
5
ꢀ
3
ꢀ
ꢀ
ꢀ
ꢀ46ꢀ J.-H.ꢀLi,ꢀW.-J.ꢀLiu,ꢀandꢀY.-X.ꢀXie,ꢀJ. Org. Chem.,ꢀ2005,ꢀ70,ꢀ5409.
ꢀ47ꢀ A.F.ꢀdeꢀSouza,ꢀA.C.ꢀSilvaꢀandꢀO.ꢀA.ꢀC.ꢀAntunes,ꢀAppl. Organomet. Chem.,ꢀ
2009,ꢀ23,ꢀ5.
PAPER:ꢀJC090760
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11/12/2009 15:36

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