dimedone双甲酮合成实验

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1、.Title:TheSynthesisofDimedoneandtheDeterminationofitsTautomericEquilibriumConstant...1.Introduction/BackgroundDimedoneiswhiteorgreendiamond-shapedorneedle-shapedcrystals,whichisinsolubleinwaterbutsolubleinethanol,methanol,chloroform,aceticacid,benzeneand50%a

2、lcoholsolution.Itcanbeusedforidentificationofaldehyde,andasrawmaterialforsynthesisoforganicandheterocycliccompounds.Dimedonehastwodifferentstructurewhichisisomers.Theywouldchangetoeachother.：Dimedonecanbesynthesizedfromdiethylmalonateandmesityloxide.Itinclud

3、esfourreactions:1)Michaeladdition2)Cyclisation3)Hydrolysisoftheester4)decarboxylation1）MichaelAdditionReaction·Itisa1,4-conjugateadditionreactionthatisreversibleandhightemperatureisgoodforreversereaction.·Thereactioniscarriedoutbetweencompound(donor)whichisa

4、bletoprovideanucleophilccaranionandanothercompound(acceptor)capabletoprovideanelectrophilicconjugatedsystemsuchasαβ-unsaturatedaldehydes,ketone,nitrile,nitrocompoundsetc.underalkalinecatalysts.·Conventionalcatalystsaretriethylamine，pipecolic，sodiumhydroxide，

5、sodiumethoxide，potassiumtertiarybutoxide....2）DieckmannReaction（Cyclisation）·ThereactionisClaisenreactionoccurredinonemoleculewithtwoester.·Itisnucleophilicsubstitutionreactionbycarbonanion.·Itisalsoreversible.·Esterreactswiththecompoundwhichhasactivemethylo

6、rmethyleneunderalkalinecatalysistogenerateβcarbonylcompound.1.Objectives1）TolearnthemechanismofMichaelAdditionreaction，Dieckmann-typecondensation，theConjugateadditionreactions，andDecarboxylation.2）Tolearntautomerismanddeterminetheketo-enolequilibriumconstant

7、byNMR...1.Mechanism1)MichaelAdditionReaction:·Carbonanionwasgeneratedunderstrongbase.·Carbonanionandreceptoroccurred1，4conjugateadditionreaction.·Theadductformedalcoholwithaprotonfromthesolvent.·Tautomerismoccurs....1)Cyclisation2)Hydrolysisoftheester·Therea

8、ctionbelongstonucleophilicaddition-eliminationmechanism....1)Decarboxylationstep·β-ketoacidiseasytobedecarboxylatedandfollowscyclictransitionstatemechanism.·Concertedreactionbyasix-memberedring.