IMPORTANT:ReadBeforeusingRieke Zinc
®
GuidetoHandlingRiekeZincinTHF
Introduction
Rieke®Zincishighlyreactiveandismoisture
andoxygensensitive.Therefore,itis
importanttoexcludeatmosphericmoisture
andoxygenfromthereactions.Thisguide
containsthebareminimumamountof
knowledgerequiredtouseRieke®Zinc.Ifone
isunfamiliarwithinertatmosphere
techniques,westronglyadviseconsultinga
definitivesourceonthemanipulationofair
sensitivereagentsbeforeusingthismetal.
Onceinertatmospheretechniquesare
mastered,Rieke®Zinccanbesuccessfullyand
easilyappliedtomanynewsynthetic
strategies.
InertAtmosphereManipulations
Theminimumequipmentnecessaryforusing
Rieke®Zincincludesanargonornitrogen
source(bestresultsareobtainedusinghigh
qualitynitrogenorargon),aflaskequipped
withasidearmtowhichaseptumcanbe
attached,andcannulaneedles.However,a
tankofnitrogenorargonwitharegulatoris
sufficienttoutilizetheactivezinc.Itis
desirablebutnotnecessarythatamanifold
withbothargon,ornitrogen,andvacuum
sourcebeused.
Cannulaneedlesshouldbestoredinanoven
untilneeded.Allequipmentshouldbepredriedinanovenat125°Covernightand
removedjustbeforeuse.Ifamanifoldwith
inertgasandvacuumsourcesisavailable,
achievinganinertatmosphereissimple.The
assembledglasswareisattachedtothe
manifoldandvacuumedandrefilledwith
argonornitrogenthreetimes.Thesystemwill
thenbeunderasuitableinertatmosphere.If
nosourceofvacuumisavailable,assemblethe
glasswareandpurgeitforaleast15-20min
withinertgas.Topurgethesystem,usealong
needleattachedviarubbertubingtotheinert
gassourceofargonornitrogenfroma
cylinderequippedwitharegulatoradjustedat
threetofivepsi.Piercetheseptumtoadd
inertgastothereactionvessel.Insertanother
needleinthesameseptumtoallowanoutlet
forthegas.
CannulaTransferofRieke®ZincinTHF
Toperformacannulatransferfromareagent
bottle,purgetheflushingneedlewithinert
gas.Thebottleshouldbeinvertedandshaken
vigorouslyseveraltimesandpressurizedby
insertingtheflushingneedle.Thecannula
needleisinsertedintothecapandtheinert
gasisallowedtoflushthecannulafor1-2min.
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Alwaysmakesurethecannulaisstoredinan
ovenuntiljustpriortouse.Oncethecannula
hasbeenflushedwithinertgas,theotherend
ofthecannulaneedlecanbeinserted
throughaseptumonthereactionvessel.
Twomethodsmaybeusedtolowertheinert
gaspressureonthereactionvessel,allowing
thereagenttobetransferred.Onemethodis
tousethevacuumlineonthemanifoldto
decreasethesystempressureslightly.The
secondmethodistoclosetheinertgassource
onthemanifoldandpierceasecondneedle
throughtheseptumonthereactionflask,thus
reducingthegaspressure.
Oncethegaspressureinthereactionvessel
hasbeenslightlyreduced,thecannulaneedle
canbeloweredintothereagent.Thisshould
starttheflowoftheRieke®Zincslurryintothe
reactionvessel.Duringthetransfer,gently
swirlthereagentbottletoallowtheRieke®
ZinctobecomeuniformintheTHF.The
recommendedsizeofcannulaforthetransfer
ofRieke®Zincis14gaugeorlarger.Measuring
theamountofreagentinacannulatransferis
easilyaccomplishedbyreadingthevolume
markonthereagentbottle.
Aftertherequiredamountofthereagenthas
beentransferred,pullthecannulaneedle
abovethereagentlevel,butdonotremoveit
entirely.Oncethereagentisnolongercoming
outofthecannula,removethecannulafirst
fromthereactionflask,thenfromthereagent
bottle,andfinallyremovetheinertgasflask
underpositiveinertgaspressure.
Clean-upofexcessRieke®Zinc
Extracaremustbetakenwhencleaning
equipmentcontainingTRACEAMOUNTSof
activezinc.Alloperationsmustbeperformed
inanefficientfumehood.Washwith
isopropanolfirst,followedbywater,andthen
carefullyadddilute(3M)HCl.Fordestroying
LARGEAMOUNTSofactivezinc,isopropanolis
addedandstirredovernightfollowedby
water,andthendiluteHCl.
PreparationofOrganozincReagentsUsing
Rieke®ZincandHalides
MostprimaryalkylbromidesreactwithRieke
zincin3-4hours.Thiscanbeshortened
considerablybyrefluxing.Inmostcases,1.051.20equivalentofRieke®Zincto1.0
equivalentofalkylhalideissufficientto
achievecompleteconversiontothe
organozinc.Secondaryandtertiaryalkyl
bromidesreactwithRieke®Zincquicklyat
roomtemperatureusing1.0equivalentof
halideto1.05-1.10equivalentofRieke®Zinc.
Aryliodidesarealsoreadilyconvertedtothe
organozincreagents.Generally,1.5equivalent
ofRieke®Zincwilleffectcompleteconversion
overnightatroomtemperatureor1-2hours
underrefluxingconditions.Arylbromidesare
moredifficultandrequire2-3equivalentsof
zincandrefluxingfor2-3hours.
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References
1. Shriver,D.F.“TheManipulationofAir-sensitiveCompounds”;McGraw-HillBookCompany;
NewYork,N.Y.1969.
2. Rieke,R.D.Crit.Rev.SurfaceChem1991,131.
3. Rieke,R.D.Science1989,246,1260
Disclaimer
TheinformationinthisguideispresentedtoassistyouinevaluatingRiekeMetals’products.This
guideandmaterialssuppliedbyRiekeMetalsareintendedsolelyforusebytechnicallyqualified
persons.Wedonotguaranteefavorableresults,andweassumenoliabilityinconnectionwith
theiruse.Thisinformationisnotintendedasalicensetooperateunder,orarecommendationto
infringeuponanypatentcoveringanymaterialoruse.Thisproductisforresearchandnotfor
drug,householdorotheruses.
RiekeMetals,LLCwarrantsthatitsproductsconformtotheinformationcontainedinthisand
otherRiekeMetals,LLCpublications.Thepurchasermustdeterminethesuitabilityofthe
productforitsparticularuse.
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