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Pdc合成OrganicSyntheses,Coll.Vol.6,p.644;Vol.52,p.5ALDEHYDESFROMPRIMARYALCOHOLSBYOXIDATIONWITHCHROMIUMTRIOXIDE:HEPTANALSubmittedbyJ.C.Collins1andW.W.Hess2.CheckedbyR.T.UyedaandR.E.Benson.1.ProcedureCaution!Thereactionofchromiumtrioxidewithpyridineisextremelyexothermic;thepreparationshouldbeconductedinahood,observingtheprecautionsnoted.2.Notes1.Dipyridinechromium(VI)oxideisavailablefromEastmanOrganicChemicals.Tobeaneffectivereagent,itmustbeanhydrous.Itshouldformaredsolutionondissolutioninanhydrousdichloromethane.2.Commercialreagentgradepyridinewasused.ThecheckersusedmaterialavailablefromAlliedChemicalCorporation,BandAgrade.3.Toavoidtheaccumulationofexcess,unchangedchromiumtrioxideandrapidtemperaturerisewhenitdoesreact,theinitialtemperatureofthepyridineshouldneverbebelow10°.4.Reagentgradechromium(VI)oxidewasdriedoverphosphoruspentoxide.ThecheckersusedmaterialavailablefromAlliedChemicalCorporation,BandAgrade.5.Aglassinepaperconeorglassfunnelinsertedinthedryingtubeneckoftheflaskduringadditionsprovedsatisfactory,providedtheconeorfunnelwasreplacedfrequently.Thepapermustbediscardedcarefully,sinceitmayinflame.Addingthechromiumtrioxidefromaflaskthroughrubbertubingproveddangerousbecauseitcausedlocalexcessesoftheoxidebelowandintheneckoftheflask.Pyridineaddedtochromiumtrioxidespontaneouslyignitescausingspotfiresthatextinguishthemselvesrapidlyifthepyridinetemperatureisbelow20°andstirringisefficient.Suchfiresshouldandcanbeavoided.6.Sincethecomplexitselflosespyridineunderreducedpressureanddarkenswithsurfacedecomposition,itshouldnotbestoredundervacuumoroveracidicdryingagents.Minimalexposuretotheatmosphereisrequiredtopreventhydrationofthecomplex.Thecheckersfoundthatafree-flowingproductwasobtainedondryingforonehour.7.Commercialdichloromethanewasdriedbydistillationfromphosphoruspentoxide.Thedichloromethanemayalsobedecantedfromphosphoruspentoxidepriortouse.Smallamountsofsuspendedphosphoruspentoxidedonotseemtointerferewiththeoxidation.8.Ifthecomplexdoesnotdissolveindichloromethane,formingaredsolution,eitherthecomplexhasbeenhydratedinhandling,orthedichloromethaneisnotanhydrous.9.Afterthealcoholandcomplexarethoroughlymixed,themixturemaybestirrednearitssurfacetoavoidfoulingofthestirrerbythethick,chromium-containingreductionproduct.Alternatively,themixturemaybeswirledperiodicallytocollectthereductionproductonthesideoftheflask.10.Thereducedchromiumprecipitateissolubleinsaturatedsodiumhydrogencarbonate,butnoadditionalaldehydewasobtainedonextractingthishydrogencarbonatesolutionwithether.11.1-Heptanol,obtainedfromAldrichChemicalCompany,Inc.,wasdistilledbeforeuse,b.p.176°.12.Asecondwashingwith100ml.of5%hydrochloricacidwillreducetheamountofpyridinepresentinthefinalproductwithoutsignificantlydecreasingtheyield.13.Theproductshowsastrongbandat1720cm.?1(C=O)intheIR.GCanalysisindicatedapurityofabout94–98%,withpyridineasthemajorimpurity.3.DiscussionReferencesandNotes1.VicePresidentforChemistry,Sterling-WinthropResearchInstitute,Rensselaer,NewYork12144.2.DepartmentofChemistry,IllinoisWesleyanUniversity,Bloomington,Illinois61701.3.H.H.Sisler,J.D.Bush,andO.E.Accountius,J.Am.Chem.Soc.,70,3827(1948).4.J.C.Collins,W.W.Hess,andF.J.Frank,TetrahedronLett.,3363(1968).5.K.B.Wiberg,“OxidationinOrganicChemistry,”PartA,AcademicPress,NewYork,1965,p.142;J.Carnduff,Q.Rev.(London),20,169(1966).6.G.I.Poos,G.E.Arth,R.E.Beyler,andL.H.Sarett,J.Am.Chem.Soc.,75,422(1953).7.J.R.Holum,J.Org.Chem.,26,4814(1961).8.W.Nagata,T.Wakabayashi,Y.Hayase,M.Narisada,andS.Kamata,J.Am.Chem.Soc.,92,3202(1970);93,5740(1971).9.E.J.Corey,N.M.Weinshenker,T.K.Schaaf,andW.Huber,J.Am.Chem.Soc.,91,5675(1969).10.W.S.Johnson,C.A.Harbert,andR.D.Stipanovic,J.Am.Chem.Soc.,90,5279(1968).11.A.W.BurgstahlerandC.M.Groginsky,Trans.Kans.Acad.Sci.,72,486(1969).12.R.RatcliffeandR.Rodehorst,J.Org.Chem.,35,4000(1970).13.W.W.EpsteinandF.W.Sweat,Chem.Rev.,67,247(1967).14.K.E.PfitznerandJ.G.Moffatt,J.Am.Chem.Soc.,85,3027(1963);J.Am.Chem.Soc.,87,5670(1965).15.A.F.CookandJ.G.Moffatt,J.Am.Chem.Soc.,89,2697(1967).16.J.R.ParikhandW.vonE.Doering,J.Am.Chem.Soc.,89,5505(1967).17.D.H.R.Barton,B.J.Garner,andR.H.Wightman,J.Chem.Soc.,1855(1964).18.A.P.JohnsonandA.Pelter,J.Chem.Soc.,520(1964).19.N.Kornblum,W.J.Jones,andG.J.Anderson,J.Am.Chem.Soc.,81,4113(1959).20.R.V.OppenauerandH.Oberrauch,An.Asoc.Quim.Argent.,37,246(1949)[Chem.Abstr.,44,3871(1950)];H.-W.BerschandA.v.Mletzko,Arch.Pharm.(WeinheimGer),291,91(1958);T.Suga,K.Kihara,andT.Matsuura,Bull.Chem.Soc.Jpn.,38,893(1965);T.SugaandT.Matsuura,Bull.Chem.Soc.Jpn.,38,1503(1965).21.R.E.Partch,TetrahedronLett.,3071(1964).22.R.M.Evans,Quart.R.(London),13,61(1959).23.E.J.CoreyandD.L.Boger,TetrahedronLett.,2461(1978);E.J.CoreyandG.Schmidt,TetrahedronLett.,399(1979);E.J.CoreyandG.W.J.Fleet,TetrahedronLett.,4499(1973).