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1、B,Y-不饱和-a-酮酸酯的直接合成及其在两个环化反应中的应用Herein,wedevelopedandinvestigatedtwodirectandefficientmethodstosynthesize0,丫-unsaturateda-Ketoestersfromaldehydeandpyruvate.Initially,thisthesisgivesacomprehensivedescriptionoftheresearchanddevelopmentofB,丫-unsaturateda-Ketoestersinrecentyears.Welaterfocusonthesynthesi
2、sof0,丫-unsaturateda-KetoestersfromaromaticaldehydeandpyruvatepromotedbyBF3.Et2Oandaceticanhydrideasadehydrant.Thisonepotreactionprotocolaffordedgoodtoexcellentyieldundermildconditionswitharomaticandsomebranchedaliphaticgsubstituted0,Y-unsaturateda-Ketoesters.Moreover,weexploredasimilarprotocoltosynt
3、hesizethelinearalkyl0,丫-unsaturateda-KetoestersfromlinearaliphaticaldehydeandpyruvatewithtetraethyltitanateTi（OEt）4actingasboththepromoteranddehydrant.ThisdirectsyntheticmethodisbasedontheAldolcondensationofethylpyruvateintheappropriateLewisacidcondition.Thesyntheticroutehascertainadvantagescompared
4、tothereportedsyntheticmethods,inthat,thereactionisonepot,theconditionsfavorable,affordedmoderatetoexcellentyield,andmoreimportantly,thereactioniseffectiveforbothaliphaticandaromaticaldehydes.Furthermore,Huisgenzwitterionsaregenerallyknowntoeffectspecialandefficientroutestoaza-heterocyclesthereforeth
5、isthesisexploredandinvestigatedtheapplicationofB,丫-unsaturateda-KetoesterswithrespecttoHuisgenzwitterion.ThemethodincludesinterceptingtheHuisgenzwitterionderivedfromtriphenylphosphineanddiisopropylazodicarboxylateDIADwithB,y-unsaturateda-Ketoesters,toform1,2,3-tricarboxlatepyrazole.Theprotocolwassuc
6、cessfulwithbothelectronwithdrawinganddonatinggroupssubstituted0,丫-unsaturateda-Ketoestersandaffordedthedesiredproductsinexcellentyields.Finally,wealsoinvestigatedtheapplicationofB,丫-unsaturateda-Ketoesterswith4-phenylbut-3-yn-2-onepromotedbyvariouscatalystthroughMichaeladditionAnnulationreactiontosy
7、nthesize3,4-dihydro-2H-pyran-2-carboxylatederivativesundermildreactioncondition.Severalcatalystscouldbeappliedinthisprotocol.ChiralandRacemiccatalystscouldbeemployedtopromotethereactioningoodyield.ThisprotocolaffordedustheadvantagesofabroadsubstratescopeofsubstitutedaromaticB,丫-unsaturateda-Ketoestersandhelpsustoavoidtheuseofexpensivetransitionmetalsascatalystinthesynthesisofpyranderivatives.
