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1、IndoleSynthesisbyControlledCarbolithiationofo-AminostyrenesAlbaneKessler,ClaireM.Coleman,PatchaneeCharoenying,²andDonalF.O'Shea*CentreforSynthesisandChemicalBiology,ConwayInstitute,DepartmentofChemistry,UniversityCollegeDublin,Belfield,Dublin4,Irelanddonal.f.oshea@ucd.ieReceivedJ
2、uly25,2004Aneffectivesynthesisofthefunctionalizedindoleringsystemhasbeendevelopedfromsubstitutedo-aminostyrenestartingmaterial.Ourmethodologyinvolvesanovelcascadereactionsequenceofalkyllithiumadditiontothestyrenedoublebondandsubsequenttrappingoftheintermediateorganolithiumwithasu
3、itableelectrophile,followedbyaninsituringclosureanddehydrationtogeneratetheindolering.Thisnewreactionsequenceallowsfortheintroductionofmoleculardiversityatallpositionsontheindolescaffold.TheprocedurewasshowntobesuccessfulwitharangeofbothCandNsubstituentsontheo-aminostyrenes.There
4、actionsequencewastoleranttothereactivityrangeofalkyllithiumssuchastert-,sec-,andn-butyllithium.TheelectrophilesusedwereDMF,whichgeneratedindoleproductswithC-2unsubstituted,andnitriles,whichincorporatedthenitrilesubstituentatC-2.Theo-aminostyrenestartingmaterialsweregeneratedbyaPd
5、-catalyzedcross-couplingreactionofavinylboronicacidequivalentwiththereadilyavailablesubstitutedo-bromoanilines.IntroductionSCHEME1.CarbolithiationofUnactivatedAlkenesThesyntheticpotentialofthecarbolithiationofun-activatedalkenesliesinthefactthatbothanewcarbon-carbonbondandorganol
6、ithiumcompoundaregeneratedintandem.Thenewlygeneratedorganolithiumspeciesmaythenbeexploitedforfurtherinsitutransforma-tions.1Adrawbackofthisapproachisthatitcansufferinitsapplicationasaviablesyntheticmethodduetothereactivityofthegeneratedorganolithiumtowardthestartingalkene.Ifthege
7、neratedorganolithiumreactswithasecondmoleculeofthealkeneananionicpolym-alkyllithium.Therateofcarbolithiationisfasterfortheerizationprocesscouldpropagate.Assuch,oneofthemoresubstitutedalkylgroup;thus,polymerizationcanearlierdemonstratedapplicationsoforganolithiumreac-beavoidedfort
8、ert-andsec-butyllithiumwhichreacttotions
