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1、C.M.GampeLecture29:LewisAcidCatalysisChem106LewisAcidCatalysisKeyQuestionsChristianM.GampeWhatisgoingonhere?November14,2011ZnEt2,(-)-DIAB(4mol%)toluene/hexanesOOH0°CPhHPhEtcatalyst15%ee->product95%eeIsthereacatalystthatcanperformthisreaction?OOHMeONO2
2、MeONO281%eeScopeofLectureThislecturewillfocusonthereactivityofLewis-acidicmetalcatalystsequippedwithchiralligandsandintroduceHowdoesthestereoinductiondependonthemetalused?youtothebasicprinciplesofLewisacidcatalysis.OONOMeMeMeMeHelpfulReferencesOOOO1."
3、FundamentalsofAsymmetricCatalysis",P.J.WalshandM.C.NNNNKozlowski,UniversityScienceBooks,Sausalito,CA,2009.Cu2+Zn2+tButButButBu2."ClassicsinStereoselectiveSynthesis",E.M.Carreira,L.Kvaerno,WilesVCH,Weinheim2009.ROSO3.Kürti,Czako,"StrategicApplicationof
4、NamedReactionsONOONOinOrganicSynthesis",ElsevierScience,2005.C.M.GampeLecture29:LewisAcidCatalysisChem1061.IntroductionIncontrasttothepreviouscase,thecycloadditionofacroleintoCanwejustaddchiralligandstoanygivenmetal-catalyzedcyclopentadieneisthermally
5、slowbutproceedsefficientlyat-20°Creactionandobtainhighee's?ifcatalyzedbyCu2+(1h).However,werunintoanotherproblemUnfortunately,itisnotthateasy.Sincetheexactmechanismofoftenencoutered:liganddeceleratedcatalysis.metal-catalysisisseldomunderstood,itisdiff
6、iculttodesignsuchAdditionofachiralpyridine-bisoxazolineligandrenderstheareaction.Besidescomplicationsthatarisefromcomplexreactionsenantioselectivebutalsoslowersothatlongerreactioncatalyticcycles(temperaturdependance,solventeffectsetc.)thereareanumbero
7、ffundamentalproblemstoovercome.timesarerequired(116h).TheuseofalesscoordinatingcounterBackgroundreactionsarethemainprobleminthedevelopmentionprovidesaremedy.Note,thatexcessligandneedstobeofmetal-catalyzedreactions.Forinstance,asymmetriccatalysispresen
8、ttoavoidtheracemicreactioncatalyzedbyCu2+withoutusingorgano-Liororgano-Mgreagentshaslargelyfailedsinceligand.(Alsoastrongbindingofthemetalbytheligandiscrucial)theuncatalyzedreaction(backgroundthermalreaction)isveryOCHOOHCRefficient.(Stoichiome
