金属有机催化

LETTERS

Pergamon

TetrahedronLetters44(2003)2409–2411

Synthesisofaziridinesfromiminesandethyldiazoacetatein

roomtemperatureionicliquids

WeiSun,Chun-GuXia*andHong-WangWang

StateKeyLaboratoryforOxoSynthesisandSelectiveOxidation,LanzhouInstituteofChemicalPhysics,

ChineseAcademyofSciences,Lanzhou730000,PRChina

Received28October2002;revised9January2003;accepted17January2003

Abstract—Thesynthesisofaziridinesfromiminesandethyldiazoacetateinroomtemperatureionicliquidsisreported.Thereactionsproceedreadilyundermildconditionswithhighcisselectivitiesandhighyields.©2003ElsevierScienceLtd.Allrightsreserved.

Duetotheirhighlyregio-andstereoselectivering-open-ingreactions,aziridinesarevaluedasbuildingblocksforthesynthesisofawiderangeofnitrogen-containingcompounds.1Therefore,ageneralmethodologyforone-stepformationofaziridineswouldbeveryuseful.Recently,severalgroupshavedevelopedtransitionmetalcatalyzedaziridinationsbasedon[N-(-p-toluene-sulfonyl)imino]phenyliodinane(PhI=NTs)asthenitrenesource2andtransitionmetal-catalyzedaziridina-tionprocessesusingchloramine-T(Ts-N-ClNa)andbromamine-T(Ts-N-BrNa).3Routestoaziridinesstart-ingfromimineshavealsobeenreported.Forexample,Jorgensenhasreportedreactionsofimineswithethyldiazoacetate(EDA)catalyzedbyCu(OTf)2.4Thesamereactionwasalsoeffectivelycatalyzedbymethylrhe-niumtrioxide5andLewisacidssuchasBF3·OEt2,AlCl3,TiCl46andInCl3.7ArecentreportdemonstratedthatLn(OTf)3alsocatalyzedthesynthesisofaziridinesfromiminesandEDA.8Wulffhasdisclosedan

extremelyexcitingresultinthechiralarylborate(derivedfromVAPOLandVANOL)catalyzedreactionofethyldiazoacetateandimines.9Recentexplorationoftheindustrialpotentialofgreenchemistryusingroom-temperatureionicliquids,partic-ularlythosebasedon1,3-dialkylimidazoliumcationssuchas1-n-butyl-3-methylimidazoliumtetrafluoro-borate(bmimBF4)and1-n-butyl-3-methylimidazoliumhexafluorophosphate(bmimPF6),asnovelreactionmediahasbecomeanexcitingareaofresearch.Theirutilityinalkylation,esterification,acylation,hydro-formylation,alkoxycarbonylation,hydrogenation,theBeckmannrearrangement,Baylis–Hillman,Biginelli,Diels–AlderandHeckreactionsaswellasinotherorganictransformationshasbeendemonstrated.10Herein,wewishtoreportaconvenientsynthesisofaziridinesfromiminesandEDAinionicliquidsatroomtemperature(Scheme1).

Scheme1.

*Correspondingauthor.Tel.:+86-931-827-6531;fax:+86-931-827-7088;e-mail:cgxia@ns.lzb.ac.cn0040-4039/03/$-seefrontmatter©2003ElsevierScienceLtd.Allrightsreserved.doi:10.1016/S0040-4039(03)00185-0

2410W.Sunetal./TetrahedronLetters44(2003)2409–2411Table1.Formationofazridines2a–hfromimines1a–handEDAinroomtemperatureionicliquidsaEntry1c2c34d5e6789101112

aIonicliquidbmimBF4bmimPF6bmimPF6bmimPF6bmimPF6bmimPF6bmimPF6bmimPF6bmimPF6bmimPF6bmimPF6bmimPF6Imine1a1a1a1a1a1b1c1d1e1f1g1h

R1PhPhPhPhPh

p-Me-Php-Me-Pho-MeO-Php-Cl-Pho-Cl-Php-NO2-Php-Br-Ph

R2PhPhPhPhPhPh

p-Me-PhPhPhPhPhPh

Product(yield%)b2a(82,cis:trans=29.6:1)2a(95,cisonly)2a(93,cisonly)00

2b(83,cisonly)2c(91,cisonly)2d(85,cisonly)2e(98,cisonly)2f(97,cisonly)

2g(98,cis:trans=33.7:1)2h(98,cisonly)

3a3a3a003b(3)(2)(3)

(8)

Allreactionswerecarriedoutusing0.5mmolofimineand0.5mmolofEDAin1.5mlofionicliquidatroomtemperaturefor5h.Isolatedyield,theratioofcisandtransisomerswasdeterminedbyGC–MSand1HNMR.c1mmolofimineand0.5mmolofEDA.d0.5mmolofimine,0.5mmolofEDAand0.1mmolofbmimPF6in3mlofCH2Cl2atroomtemperaturefor7h.e0.5mmolofimine,0.5mmolofEDAand0.1mmolofbmimPF6in3mlofhexaneatroomtemperaturefor7h.

bTable2.Formationofazridines2afromimine1aandEDAinbmimPF6recyclingaEntry12345

aRecycleno.12345

2a2a2a2a2a(93,(93,(93,(94,(91,

Product(yield%)bcisciscisciscisonly)only)only)only)only)

3a3a3a3a3a(3)(3)(3)(2)(4)

productswereextractedwithpetroleumetherandethylacetate(5:1)andpurifiedbycolumnchromatographyonsilicagelwithpetroleumetherandethylacetate(5:1)aseluent.Theroomtemperatureionicliquid(bmimPF6)wasdriedundervacuumforthenextrun.TheresultingproductswereanalyzedbyNMRandGC–MS.

Beingcomposedentirelyofions,ionicliquidsareimmisciblewithsomeorganicsolvents.Whenthereac-tionisover,theproductsareeasilyextractedfromtheionicliquidswithpetroleumetherandethylacetate(5:1).Theionicliquid(bmimPF6)couldbedriedundervacuumforfurtheruse.TheprocedurewasrepeatedfivetimesandtheresultsareshowninTable2.Itisobviousthattheionicliquid(bmimPF6)stillretainshighconversionandcisselectivitiesduringthefifthcycle.Inaddition,thesereactionsproceedreadilyatroomtemperatureanddonotneedanotherLewisacidpromoter,suchasBF3·OEt2,AlCl3,TiCl4,etc.Insummary,wehavedemonstratedanaziridinesynthe-sisinionicliquidsatroomtemperature.Thereactionsproceedreadilyundermildconditionsandshowhighyieldsandcisselectivity.Furtherstudyregardingthemechanismisunderway.

Acknowledgements

WethanktheNationalNaturalScienceFoundationofChinaforfinancialsupportofthiswork(29933050).

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