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时间:2020-06-18
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1、Heck反应的机理及示例机理:Heck反应的机理有一定的规律,通常认为反应共分四步:(a)氧化加成(Oxidativeaddition):RX(R为烯基或芳基,X=I>TfO>Br>>Cl)与Pd0L2的加成,形成PdⅡ配合物中间体;(b)配位插入(Cordination-insertion):烯键插入Pd-R键的过程;(c)β-H的消除;(d)催化剂的再生:加碱催化使重新得到Pd0L2。示例:Astirredsolutionof1(98mg,0.19mmol),triethylmine(0.32mL,2.3mmol)andcataly
2、tictetrakis(triphenylphosphine)palladium(0)(ca.5mg,4μmol)in2.4mLofacetonitrilewasheatedat80℃inasealedtubeunderanargonatmospherefor10h.Thereactionmixtureturneddarkorangeafterca.10min,andthecatalystplatedoutonthewallsofthetubeasashinylayerofpalladiummetaluponcompletionofth
3、ereaction.Thereactionmixturewascooledtoroomtemperature;thereactionwasquenchedwithaqueousNaHCO3(15mL),andthemixturewasextractedwithEtOAc(4×10mL).TheorganicextractswerewashedwithaqueousNaHSO3(1×15mL),water(1×15mL),andbrine(1×15mL)anddriedoverMgSO4.Filtration,concentration,
4、andpurificationoftheorangeresiduebyflashcolumnchromatography(45:55Et2O/hexanes)gave66mg(90%)of19asacolorlesssolid:mp193-194℃;Rf=0.29(8:2Et2O/hexanes).
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