预览加载中,请您耐心等待几秒...
1/4
2/4
3/4
4/4

在线预览结束,喜欢就下载吧,查找使用更方便

如果您无法下载资料,请参考说明:

1、部分资料下载需要金币,请确保您的账户上有足够的金币

2、已购买过的文档,再次下载不重复扣费

3、资料包下载后请先用软件解压,在使用对应软件打开

Tetrahedron Letters TetrahedronLetters45(2004)1441–1444 Arobustpalladium-catalyzedcyanationprocedure: beneficialeffectofzincacetate RamakrishnanChidambaram* ProcessResearchandDevelopment,Bristol–MyersSquibb,NewBrunswick,NJ08908,USA Received1December2003;revised9December2003;accepted9December2003 Abstract—ConditionsthatensureamorereproduciblePd(0)-mediatedproceduretoconvertarylbromidestoarylcyanideshave beendevelopedthatentailtheuseofzincdusttokeepthePdinthezerooxidationstateandzincacetatetoensurehighcatalytic activity.Thisprocedureisapplicabletoawiderangeofsubstratesandobviatestheneedforstringentremovalofoxygenfromthe reactionmedium. Ó2003ElsevierLtd.Allrightsreserved. Averyimportantandusefulreactioninorganicsyn-Asexpected,whentheDMFwassaturatedwithoxygen, thesisistheconversionofanarylbromideorchloridetotherewasabsolutelynoconversionofIintoII. anarylcyanide;1severalproceduresinvolvingtheuseof transitionmetalsareavailable.2Unfortunately,mostofThisimplicatedoxygenasthemainsourceindeactiva- theseproceduresrequirehightemperatures(120–tionofthecatalyst,resultinginlowerconversion.4Since 140°C),andmoreimportantly,thereactionstendtobeoxygenmostlikelyoxidizestheactivepalladium(0) capricious.speciestoapalladium(II)species,theinsituuseofa reductantmightreducethepalladium(II)backtothe Oureffortsweredirectedtowardsfindingageneralandpalladium(0)speciesandreintroduceitintothecatalytic scalableproceduretoconvertsubstitutedbromoacet-cycle.Sincezinchasbeenusedincyanationreactionsto anilideItothecorrespondingproprietarycyanocom-reducepalladium(II)species,3b;5weadded3–4mol% poundII.Thetwomostrecentlyreportedsystemsforzincdusttoourcyanationreactionandobtained suchaconversionare:excellentconversion(>99areapercent)ofIintoII withouttheneedtodeoxygenatetheDMF.Thecya- (a)Pd(OAc)2asthecatalyst,dppeasaligandandacet-nationprocedureusingzincdustwasthensuccessfully onecyanohydrinasthecyanidesource2andscaleduptoproducemulti-kilogramquantitiesofII. 0 (b)Pd2(dba)3incombinationwithdppf[1,1-bis(diph