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1、EnantioselectiveMichaelAdditionsinNaturalProductsSynthesisMacMillanGroupMeeting12December2001JulieY.ParkI.IntroductionII.EarlyExamplesIII.Misc.AuxiliariesIV.AmideEnolatesV.ChiralIminesandEnaminesVI.ChiralSulfinylIminesVII.ChiralSulfoxidesVIII.Phase-TransferCatalystsIX.HeterobimetallicCatalystsX
2、.SummaryIntroductionDefinitionofMichaeladdition:Z1R2!11RZZ2!R1Z2R2!Carbon-carbonbond-formingreaction!Additionofacompoundwithanelectron-withdrawinggroup(Z)toanactivatedC-Cmultiplebond!Excludesmetal-mediated1,4-conjugateaddition(cuprates,Grignards,lithiates,etc.)!Excludesheteroatomconjugateadditi
3、onRepresentativeMichaeldonors:ONRRRRRRSRSRNO2OOORepresentativeMichaelacceptors:ONR2RRSSRNO2OOO!Thesamefunctionalgroupsservetoactivateeitherthenucleophileortheelectrophile!AwidevarietyoffunctionalhandlesthatcanbefurtherelaboratedinsynthesisEarlyExamplesofEnantioselectiveMichaelReactionsSynthesis
4、ofopticallyactivecyclopropanes:MeOO1.KOtBuClHO2CCO2HOEtO2.KOH"60%y,"10%eeMeMe(–)-menthylchloroacetateOH-OOviaROOEtRO2CCO2EtClInouye,Y.;Inamasu,S.;Ohno,M.;Sugita,T.;Walborsky,H.M.J.Am.Chem.Soc.1961,83,2962.ChiralbasecatalyzedMichaeladditionformschiralquaternarycenter:ROONHOOOMeCO2MeROOR=H,iPropt
5、icallyactiveproductofundeterminedstereochemistryLangstrom,B.;Bergson,G.ActaChem.Scand.1973,27,3118.Auxiliary-ControlledAsymmetricInductionOppolzer'ssynthesisof(–)-khusimone:MeCO2RMeHRO2CBrMeMeLDA,MgenecyclizationMeHOR=OOOEnolatealkylation63:21:9:7dr(–)-KhusimoneStereochemicalrationale:MeMeMeMeM
6、etBuHMetBuHOHOHMeMeOOOOHOOLiAB!Alphafaceofenolateisshieldedbytheauxiliary!EnantiofacialdiscriminationoftheenonedeterminedbystericsandchelatingfactorswhichfavormodelA.Oppolzer,W.;Pitteloud,R.;Bernardinelli,G.;Baettig,K.TetrahedronLett.1983,45,4975.AuxiliaryControl:EnantioselectiveRobinsonAnnulat
7、ionTaber'ssynthesisof(+)-o-methyljoubertiamineOMeOMeOHMMVK,K2CO3ArOROHOHCH2(OMe)2/H2OArOOOOMeOO90%de,76%yieldFactorsinchoosingK2CO3asbase:!weakbasetoquenchintermediateketoneenolate!chelatingcounterionAuxiliary-aidedMichaeldonorOMe
