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1、ORGANICLETTERSPalladium-CatalyzedCross-Couplingof2004Vol.6,No.22PyrroleAnionswithArylChlorides,3981-3983Bromides,andIodidesRyanD.Rieth,NealP.Mankad,ElisaCalimano,andJosephP.Sadighi*DepartmentofChemistry,MassachusettsInstituteofTechnology,77MassachusettsAVenue,
2、Cambridge,Massachusetts02139jsadighi@mit.eduReceivedAugust16,2004ABSTRACTAgeneralmethodfortheconversionofpyrroleanionsto2-arylpyrroleshasbeendeveloped.Usingapalladiumprecatalystandstericallydemanding2-(dialkylphosphino)biphenylligands,(pyrrolyl)zincchloridemay
3、becross-coupledwithawiderangeofarylhalides,includingarylchloridesandarylbromides,atlowcatalystloadingsandundermildconditions.Ahighdegreeofsterichindranceistolerated.Certainring-substitutedpyrroleanionshavealsobeenarylatedwitharylbromidesubstrates.Inthepursuito
4、fnewlow-coordinatecomplexesoflatepharmaceuticals,4bandinsecticides,4cageneralmethodfortransitionmetals,webecameinterestedinpyrrole-derivedthearylationofpyrrolescouldbewidelyuseful.chelateligands1andintheincorporationofstericallyThegreatversatilityofPd-catalyze
5、dcross-couplingindemandingarylgroupsinthepositionsflankingthenitrogenC-Cbondformationincludessomenoteworthyroutestoatoms.Inseveralcasesofinterest,theprecursor2-aryl-2-arylpyrroles.Polysubstitutedpyrroleshavebeenpreparedpyrroleshadnotbeenreported.2,3Because2-ar
6、ylpyrrolesarebyelegantmulticomponentcouplingreactions;5lesssubsti-alsoofinterestinthesynthesisoffluorescentdyes,4atuted2-arylpyrroleshavebeenobtainedbySuzukicross-couplingofN-protectedpyrrolederivatives.6,7Thepyrrole(1)Selectedrecentexamples:(a)Halper,S.R.;Coh
7、en,S.M.Angew.Chem.,Int.Ed.2004,43,2385-2388.(b)Gao,G.;Korobkov,I.;anion,asits(chloro)zincderivative,coupleswithiodoben-Gambarotta,S.Inorg.Chem.2004,43,1108-1115.(c)Love,J.B.;Salyer,P.A.;Bailey,A.S.;Wilson,C.;Blake,A.J.;Davies,E.S.;Evans,D.J.Chem.Commun.2003,13
8、90-1391.(d)Li,Y.;Turnas,A.;Ciszewski,J.(3)Ourattempttosynthesize2-mesitylpyrrole,forexample,byadaptationT.;Odom,A.L.Inorg.Chem.2002,41,6298-6306.(e)Chen,Q.;Dolphin,ofanexistingrout
