Claisen Rearrangement of Allyl Phenyl Ether. 1一14C and β-14C Kinetic Isotope Effects. A Clearer View of the Transition Struct.docx

1、.SOO=Bp<Dqs=qndalccqs>oo-2M0J=uosuo=dos<D.Eop388u-cBqs、£?o.soc3.sqndsd工q00suHn)一切W9W一ZOZoozbqEM0NU0>INQ5HN<.2AP0pgcM0aClaisenRearrangementofAllylPhenylEther.1-14Cand/3-14CKineticIsotopeEffects.AClearerViewoftheTransitionStructureLidiaKupczyk-Subotkowska,1WitoldSubotkowski?William

2、H.Saunders,Jr,“andHenryJ.Shine*4*ContributionfromtheDepartmentofChemistryandBiochemistry,TexasTechUniversity,Lubbock,Texas79409,andDepartmentofChemistry,UniversityofRochester,RiverStation.Rochester,NewYork14627.ReceivedOctober28,1991reomcricexcesshadoccurredduringthesesynthetictransformations.TheSAM

3、PhydrazonewasthenalkylatedwithethyliodideandsubjectedtobasiceliminationwithDBNat-78°C.Theconversionofhydrazone(S$)17tonitrile(S)-7tookplaceinonlyfairyield,andnoattemptwasmadetoimprovethisreaction.Theoverallyieldof(S)-7from(SS)-13awas25%.Althoughnodirectmeasureofecwasmadeon(S)7,itispresumedtobei

4、ntherangeof70-85%basedonresultsobtainedwithmonomer(，4.Followingsilicagelchromatography(S)7wasobtainedinanalyticallypurestateandhadidenticalspectralcharacteristicstoitsracemate.PhysicalMethodsofCharacterization.Differentialscanningcalorimetry(DSC)experimentswereconductedwithaPerkinElmerDSC4differenti

5、alscanningcalorimeter.Typically,heatingandcoolingratesof10°CminHwereemployed.SamplesforDSCexperiments(2-7mg)werepreparedinhermeticallysealedaluminumpans.MicroscopicobservationsweremadeonaLcitzLaborlux12polpolarizingmicroscopecoupledtoaLeitzhotstage,controlledbyaResearch,Inc.thcrmocon-trollcr.Sa

6、mpleswerepreparedoncleanglasssurfacesbymeltingasmallparticleofthematerialonthesurfaceatanappropriatetemperature.Asecondglasscoverslipwasplacedontopofthedroplet,andthesamplewasflattenedintoathinfilm.Acknowledgment.ThisworkwassupportedbyagrantfromtheDepartmentofEnergy,DEAC0276ER01198,obtainedthroughth

7、eMaterialsResearchLaboratoryattheUniversityofIllinois.SupportforJ.S.M.fromAT&TBellLaboratoriesthroughagraduatefellowshipisalsogratefullyacknowledged.AppendixFigure9showsaschemefordeducingthestructuresofcondensationmacromoleculesatthelevelofregiochemicalorder.ChainsegmentsarerepresentedastheirFis

8、herprojectionswhereindividualmonomerunitsareassembledwithagenericlinkinggroupsymbolizedasThedetailedstructureofthelinkinggroupisnotimportantforthefollowingdiscussion.Beginningwithahighlysubstituted,highlysymmetricchain,removalofsubstituentsinanorderlyfashionwilluncoverthevariouslevelsofmacromolecula

9、rstructure.Removingapairofsubstituentsfromeachmonomerunitsuchthateachpairisremovedfromequivalentpositionsinadjacentmonomersleavestheisoregicbackbone.Thisstructureischaracterizedbyitspolartranslationalsymmetry.Similarly,removingapairofsubstituentsfromeachmonomerunitsuchthateachpairisremovedfromnonequ

10、ivalentpositionsinadjacentmonomersleavesthesyndioregicteckbone.Thisstructureischaracterizedbyitsapolartranslationalsymmetrywithaperiodicityoftwomonomerunits.Thearegicbackboneisobtainedbyrandomlyremovingpairsofsubstituentsfromeitherequivalentornonequivalentpositionsinadjacentmonomerunits.Chainsofthis

11、typearenotcharacterizedbyasinglestructurebutinsteadbyasetofpossibleconstitutionalisomers.Thearegicbackbonethusbelongstothefamilyofchemicallydisorderedpolymers.Figure10showsaschemefordeducingthechiralformsofcondensationmacromolecules.UsingFigure9asastartingpoint,stereogenicelementscanbeintroducedbyfu

12、rtherremovaloftheremainingsubstituentsoneachchain.Itcanbeseenthateachoftheregiochemicalstructurescanexistinconfigurationallyordered(toprow,Figure10)aswellasconfigurationallydisorderedforms(bottomrow,Figure10).Lookingfirstatthedisorderedforms,itisinterestingtonotethatitispossibletohavecompletestereoc

13、hemicalandregiochemicalorderandstillhaveanachiralbackbone.Themesoisoregicandthemesosyndioregicstructuresaresuchexamples.Themesoisoregicbackbonecontainsaglide-reflectionaxisalongthechaindirection,whilethemesosyndioregicpossessesmirrorplanesperpendiculartothebackbone.Theconfigurationallydisorderedform

14、softheisoregicandsyndioregicbackbonesaswellastheconfigurationallydisorderedaregicbackbonearesystemsbestdescribedasasetofpossiblediastereomericisomers.SupplementaryMaterialAvailable:Syntheticproceduresforvariousintermediatesandcorrespondingcharacterizationaswellasgeneralinformationonspectroscopicandc

15、hromatographicprocedures(42pages).Orderinginformationisgivenonanycurrentmastheadpage.Abstract:Thekineticisotopeeffects,Jt12C/Zc14C,fortherearrangementsofallyll-14Cphenyletherand/3-l4Callylphenyletherhavebeenmeasured:1.0119±0.0009and1.0148士0.0005,respectively.Theseresults,alongwiththosereportede

16、arlierforl8O,2-14C,a-I4C,andy-14C,representthefirstcompletekineticisotopeeffect(KIE)descriptionofapericyclicsystem.Modelingcalculationshavebeenappliedtotheheavy-atomKIEandthepreviouslyreporteddeuteriumKIEtodefinethetransitionstructureofthereanangementmoreexplicitly.Thecalculationsconfirmourearlierde

17、scriptionthattheCa-Obondis50-60%brokenwhiletheCT-Corthobondis10-20%formedandnowprovidesignificantlymoreinsighttothedynamicsoftherearrangement.Couplingbetweenthephenoxyandallylfragmentsisstronger,andwithinthefragmentsisweaker,thanpreviouslysupposed.IntroductionRecently,wereportedkineticisotopeeffects

18、(KIE)forthefouratomsthataredirectlyinvolvedinbondbreakingandbondforminginthethermalrearrangementofallylphenylether.Kupczyk-Subotkowska,L.;Saunders,W.H.»Jr.;Shine,H.J.J.Am.Thatis,wemeasuredthe18Oanda-14CKIEofbondbreakingandtheortho-Cand7-14Cofbondforming.Theresultswerecombinedwitha-andy-deuteriu

19、mKIEthathadbeenreportedearlierbyMcMichaelandKorverChent.Soc.1988,110,7153.tocharacterizethetransitionstructure(1) TexasTechUniversity.(2) UniversityofRochester.(2)UniversityofRochester.Chem.Soc.1988,110,7153.0002-7863/92/1514-3441$03.00/01992AmericanChemicalSocietySchemeIC>H<OH1.UAIH4CHCOOHh-C

20、HCOOCjHsh3。4248%H8r,HjSQch2(ch2bt)2NaOHOCH/CH2CH2Br0isotopeKIEisotopeKIE18。1.0297-1-I4C1.0148a-,4C1.0306。2-14C1.0375°c1.0119a-2H21.18t-14c1.0362°y-2h20.958aReference3.bReference4,at180°C.TableII.AveragedKIEfortheRearrangementof1into2minorchangeshavebeenmadetokeep3and4consistentwith5an

21、d6,butthesedidnotsignificantlyalterKIEcalculatedusingthesamebondcouplingsasbefore?TableI.KineticIsotopeEffects(KIE)fortheThermalRearrangementofAllyl1-,4CPhenylEtherand|8-I4CAllylPhenylEtherinDiphenylEtherat220°ClabelexptconvKIE1-,4C10.271.0115±0.00170.201.0120±0.00200.181.0106±0.

22、00081-14C20.301.0114±0.00120.231.0124±0.00150.151.0135±0.0017mean1.0119±0.000930.291.0136土0.00110.251.0168±0.00170.161.0142±0.00113-l4C40.271.0135土0.00110.221.0149±0.00110.161.0148±0.0015mean1.0148土0.0005I.AflOH2heatingto160Bc'3R3T8ofthiswell-knownsigmatro

23、picrearrangement.3Itwasfoundbycutoff-modelcalculationsthattheCa-0bondwas50-60%brokenwhileCYorthobondformationwasonly10-20%completeinthetransitionstructure.Duringthecourseofthesecalculations,itbecomesapparentthatsubstantialKIEshouldalsobeexperiencedattheC1andC.positions.Thatis,thecalculationsindicate

24、dthatKIEfortheseatomsshouldresultfromcoupledmotionthroughoutthesix-atomarrayofthispericyclicsystem.Therefore,wesetouttomeasuretheseKIEandhavesubstantiatedtheindications.Substantial1-14Cand/3-14CKIEhavebeenfound.Wereportthemhereandusethemwiththeearlierheavy-atomanddeuteriumKIEtorefineourviewofthetran

25、sitionstructureoftherearrangement.ResultsAllyll-l4Cphenylether(1-14C-1)waspreparedfrom4-nitrol-14Cphenolinstandardways./3-14CAllylphenyletherwasprepar曲infivestepsasshowninSchemeI.Thekey,labeledintermediateinthesestepswas2-14C-1,3-propanediol.Attemptstoprepare1,3-propanediolingoodyieldbydirectreducti

26、onofmalonicacidwithLiAlH4wereunsuccessful,anditwasfoundtobeexpedienttoreducethediethylester.Standardprocedureswereusedinallothersteps.Rearrangementsof1into2werecarriedoutat220°Casdescribedearlier,3andtheisolated2wasconvertedintoitsphenylurethaneforpurificationbysublimationandscintillationcounti

27、ng.TheKIEarelistedindetailinTableIandaresummarizedwiththosereportedearlierinTableII.CalculationsThemodelcalculationswerecarriedoutasbefore,3usingthebebovib-ivprograminaversioncompiledtorunonaMacintoshIIcomputer.567Themodels3R3TSand4R4TScorrespondto56and78,respectively,intheearlierwork.3Afew4TSWhenmo

28、dels3and4wereusedtocalculatethe伊4Cand1-14Ceffects,theresultingvalueswerequitelarge:ontheorderof1.03-1.04inbothcases.Thesemodelsare,however,nottruecutoffmodels6,7withrespecttotheseeffects,andthevaluesarethusofuncertainreliability.Furtherelaborationof3and4tomakethemtruecutoffmodelsforalloftheobservede

29、ffectswouldrequirecyclictransitionstructures.Aswehavepointedoutbefore,3cyclictransitionstructuresintroduceredundanciesthatconsiderablycomplicatetheperformanceandinterpretationofthecalculations.8Consequently,wedecidedtousetwoadditionalmodels,5R5TSand6R一6TStocalculatethe3J4Cand1-14Ceffects.»u,CH5

30、R5TSTableIII.CalculatedIsotopeEffectsforStrongCouplingwithinAllylandPhenoxyFragments0aamnvalues0.8,0.5,0.5,0.8formodels3and4,0.5,0.8,0.5formodels5and6.Theorderisthatofthenumberedbondsinthecorrespondingstructures.TunnelcorrectionscalculatedfromthefirsttermoftheBellequationareincludedinallisotopeeffec

31、ts,butchangetheeffectsbylessthanexperimentalerror.(CO)/a(CC)】8°a-da-l4Cv-,4cy-dorthoC1-14CDev(hvy)Dev(H/D)0.5/0.21.03081.16101.03381.04961.03980.93931.03771.03820.01940.01960.5/0.11.03081.16101.03381.04541.04610.96921.04041.03580.01780.02580.4/0.31.03091.19511.03671.05121.03860.93831.03841.0396

32、0.02040.01780.3/0.31.03091.23181.04011.05021.04280.96531.04261.03970.02060.04680.4/0.21.03091.19511.03671.04891.04410.96571.04221.03830.01960.0209exptl1.02971.181.03061.01481.03620.951.03751.0119TableIV.CalculatedIsotopeEffectsforStrongCouplingbetweenAllylandPhenoxyFragments。(CO)/(CC)18。a-da-,4C3-,4

33、Cy-,4Cy-dortho-AC1-,4CDev(hvy)Dev(H/D)0.5/0.21.03161.16541.03541.02311.03570.93911.02541.01820.00730.01690.5/0.11.03161.16541.03541.01991.03810.96351.02761.01640.00540.01880.4/0.31.02991.19801.03661.02481.03700.94121.02701.01940.00760.0178O.3/O.31.02791.23211.03761.02421.04110.96831.03091.01950.0071

34、0.04820.4/0.21.02991.19801.03661.02271.04000.96581.02941.01830.00650.0226exptl1.02971.181.03061.01481.03620.951.03751.0119aamnvalues0.4,0.65,0.65,0.4formodels3and4,0.75,0,45,0.75formodels5and6.Theorderisthatofthenumberedbondsinthecorrespondingstructures.Tunnelcorrectionscalculatedfromthefirsttermoft

35、heBellequationareincludedinallisotopeeffects,butchangetheeffectsbylessthanexperimentalerror.Asbefore,off-diagonalFmatrixelementswereintroducedtoachieveanimaginaryreactioncoordinatefrequencyinwhichbondingchangeswereoccurringinsuchawayastotransformthetransitionstructurestoproducts.Melander,L.;Saunders

36、,W.H.,Jr.ReactionRatesofIsotopicMoleculesWiley-Interscience:NewYork,1980;pp64-66.Theoff-diagonalelementsarecalculatedfromeq1,andtheamnvaluesformodels3and4aregivenbyeq2.Adifferentrelation,eq3,isrequiredformodelsFmn=Gm(&也)11-酣2-成3-慮4一屏5+希24+層2角5+屆3廚5=。1*2.2-JL_22八q_勺2_«23_“34丁U12M34_"5an

37、d6becausetheycontainfourratherthanfiveconsecutivereactingbonds.Asaresult,usingthesamesetofvaluesforcorrespondingbondcouplingsinmodels3and4ontheonehand,and5and6ontheother,canleadtoimaginaryfrequenciesofquitedifferentmagnitudes.Toavoidthisphysicallyunrealisticsituation,wechosevaluesforourmodels(except

38、thosereportedinTableII)asfollows.Couplingswithintheallylandphenoxyfragments(a12anda45in3TSand4TS,anda23in5TSand6TS)wereassignedsimilarbutnotidenticalvalues.Couplingsbetweenthefragments(a23anda34in3TSand4TS,anda12anda34in5TSand6TS)wereassigneddifferentsetsofvalues,butagainvaluesthatweresimilarforallb

39、etween-fragmentcouplings.Thus,correspondingamsindifferentmodels(e.g.,a34in3TSand5TSora23in4TSand“34in6TS)werenotnecessarilythesame,buttheratiosofamsforadjacentMwithin-fragmentwand“between-fragment”couplingswerekeptreasonablysimilar(e.g.,“12/23in3TSanda/alxin6TS).Inthiswaywecouldallowthecouplingstova

40、rysoastogivegoodfitstoalloftheexperimentalresults,withouttreatingascompletelyindependent,couplingsthatphysicallyarenot.Ouradjustableparameters,then,arethen(CO),n(CC),andamnvalues.Webeganwithasetoffive(CO)andn(CC)valuesthatledtothebestagreementswiththesixexperimentalisotopeeffectsquotedpreviously.1Th

41、einitialsetofamnvalueswerethesameasthoseofTableVIIinref1.TheresultsaregiveninTableIII.Beforediscussingtheseresults,somecommentonthecriteriaforgoodnessoffitisinorder,Previously,wesimplycomparedonebyonetheisotopeeffectpredictionsofagivenmodelwiththecorrespondingexperimentalvaluesandrejectedthemodelifo

42、neormoreofthepredictionswasoffbyasignificantamount.Thisapproachbecomesincreasinglycumbersomeandsubjectiveasthenumberofcomparisonstobemadeincreases.Consequently,thelasttwocolumnsofeachtablegivedeviationscalculatedfromeq4.Theformofeq4isessentiallythesameasthatoftheDev=(E(exptl-calcd)/exptl)2/(n-l)2(4)

43、1equationusedtocalculaterelativestandarddeviations(replacementof“ealed”by"mean”and"Dev”by"條wouldmakethemidentical).ThesignificanceofDevis,ofcourse,differentfromthatofbutitsvalueshavetheadvantageofbeingcomparableinmagnitudetorelativestandarddeviations.Theheavy-atomandH/Deffectsaretreat

44、edseparatelybecausetheuncertaintyinthelatterismuchgreaterthanintheformer.Forexample,anexperimentaluncertaintyof±0.02inthetwoH/DeffectsistobeexpectedandcorrespondstoDev(H/D)=0.0270.Theexperimentaluncertaintyintheheavy-atomeffectsishardertopindown.Uncertaintiesinindividualvaluesrun0.001-0.004(Tab

45、leIofref1andTableIofthepresentpaper).Themoststringentmeasureofprecision,therangeofrepeateddeterminations,isusuallynomorethan0.004-0.006,thoughinafewcasesitiswider.Anaveragedeviationof0.004fortheheavy-atomeffectscorrespondstoDev(hvy)=0.0043andadeviationof0.005toDev(hvy)=0.0053.Thesewouldseemtobereaso

46、nablevaluestoaimfor,whilereservingtherighttorejectmodelswheremosteffectsarepredictedverycloselybutoneissignificantlyoff.Thesquaringof(exptl一ealed)ineq4infacttendstosignalsuchasituationbyexaggeratingthecontributionsofverypoorfitstothesum.ReturningtoTableIII,itisimmediatelyevidentthatthecalculated3-l4

47、Cand1-14Ceffectsaremuchlargerthantheexperimentalones.Ourpredictionofsignificant/3-l4Cand1-14Cisotopeeffectsisobviouslybornoutbyexperiment,butmodelsthatpredictedtheothereffectswellareclearlyunsatisfactorywhenconfrontedbythenewdata.Ourpreviousexperiencetellsusthatthemagnitudesoftheheavy-atomeffectsare

48、quitesensitivetothecouplingsused;thelargertheamnvaluecouplingthetworeactingbondstoagivenatom,thelargertheisotopeeffectfromthatatom.Thus,itwasclearthatweneededtoreducethewithin-fragmentbondcouplingsinordertobringthe3-14Cand1-I4Ceffectsclosertotheexperimentalvalues.Aconcomitantincreaseinthebetween-fra

49、gmentcouplingsisnecessarytoretainanimaginaryreactioncoordinatefrequency(negativeZ>ineqs2and3).Aspredicted,thischangereducedthecalculated8-14Cand1-14Ceffectstovaluesinreasonableagreementwiththeexperimentalones,butatthesametimethrewoutofagreementsomeoftheothereffects.Afterconsiderableexperimentatio

50、n,promisingresultswereobtained.ThebestvaluesinTableIV(for*(CO)/n(CC)=0.5/0.1)showanaverageerrorintheheavy-atomlargertheamnValuecouplingthetworeactingbondstoagivenatom,thethelargerisotopeeffectfromthatatom.Thus,itwasclearthatweneededtoreduce腿within-fragmentbondcouplingsinorder"bringthe/s-ucand1-

51、14Ceffectsclosertotheexperimentalvalues.Aconcomitantincreaseinthebetween-fragmentcouplings'snecessarytoretainanimaginaryreactioncoordinatefrequency(negativeDineqs2and3).Aspredicted,'schangereducedthecalculated/9-14Cand1-!4C.theeffectstovaluesinreasonableagreementwithexperimentalones,butatthe

52、sametimethrewoutofagreementsomeoftheothereffects.Afterconsiderableexperimentation,promisingresultswereobtained.ThebestvaluesinTableIV(for«(CO)/«(CC)=0.5/0.1)showanaverageerrorintheheavy-atomTableV.CalculatedIsotopeEffectsforBestModelwithStrongCouplingbetweenAllylandPhenoxyFragments0aamnval

53、ues0.4,0.72,0.57,0.4formodel3,0.4,0.73,0.57,0.4formodel4»0.8,0.4,0.75formodel5,and0.75,0.4,0.8formodel6.Theorderisthatofthenumberedbondsinthecorrespondingstructures.Tunnelcorrectionscalculatedfrom(hefirsttermoftheBellequationareincludedinallisotopeeffects,butchangetheeffectsbylessthanexperiment

54、alerror.n(CO)/n(CC)18。a-da-,4C時，C"Cy-dortho-C1-,4CDev(hvy)Dev(H/D)0.9/0.11.04121.04431.02611.01831.02400.86861.01441.01510.01260.1434O.7/O.31.03821.10061.02901.02321.02580.86871.01841.01730.01100.10890.5/0.51.03451.16201.03211.02561.02570.87021.02081.01860.01040.08540.3/0.71.02991.22921.03501.0

55、2601.02540.87451.02271.01960.01010.08980.1/0.91.02361.30251.03691.02341.02510.88221.02431.01940.00980.12600.7/0.21.03821.10061.02901.02051.02910.89171.02051.01560.00930.09110.7/0.11.03821.10061.02901.01731.03150.91491.02181.01390.00810.07680.6/0.31.03651.13061.03061.02261.02960.89221.02221.01660.008

56、70.07390.6/0.21.03651.13061.03061.02001.03300.91591.02431.01540.00710.05520.6/0.11.03651.13061.03061.01711.03540.93971.02561.01380.00610.04320.5/0.41.03451.16211.03211.02401.02970.89301.02361.01740.00840.06190.5/0.31.03451.16211.03211.02211.03350.91671.02601.01650.00670.03820.5/0.21.03451.16201.03211.01971.03700.94121.02811.01540.00530.01780.5/0.11.03451.16201.03211.01691.03940.96581.02941.01370.00450.02260.4/0.31.03231.19491.03361.02161.03750.94251.02991.01660.00520.01490.4/0.21.03231.19491.03361.01941.04100.96781.03201.01540.00440.02260.4/0.11.032