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1、PREPARATIONOF-ACETOXYETHERSBYTHEREDUCTIVEACETYLATIONOFESTERS:endo-1-BORNYLOXYETHYLACETATE[(Ethanol,1-[[(1R,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]oxy]-,acetate)]OH3CCH31.DIBALHH3CCH3CH3OCH2Cl2,–78°C,45minCH3OCH32.pyr,DMAP,Ac2OOCH3CH2Cl2,–78°Cto0°C,12hrOCH31Submi
2、ttedbyDavidJ.KopeckyandScottD.Rychnovsky.CheckedbyGuillaumeL.N.Péron,CédricR.N.Fischmeister,andAndrewB.Holmes.DiscussionAddendum:Org.Synth.,2012,89,143.1.ProcedureAflame-dried,2-L,three-necked,round-bottomedflask,equippedwithalargeTeflonmagneticstirringbarandthreerubber
3、septa,ischargedwith5.5g(28.1mmol)of()-bornylacetate(Note1)in162mLofdichloromethane(Note2)underanargonatmosphere.Athermocouple(Note3)isimmersedinthesolutionthroughoneoftherubbersepta.Theflaskisplacedinadryice/acetonebathandcooledtoaninternalsolutiontemperatureof78°C.St
4、irringisbegunanddiisobutylaluminumhydride,54.4mLofa1.0Msolutioninhexanes(54.4mmol,2eq),isaddedasaslowstreamviaaglasssyringeoveraperiodof13min;duringthisaddition,theinternalsolutiontemperaturedoesnotexceed72°C(Notes1,4).Theclearsolutionisstirredforanadditional45minat78
5、°C,then6.6mLofpyridine(6.5g,81.6mmol,3.0eq)isaddeddropwiseviaaglasssyringe,maintainingtheinternaltemperaturebelow76°C.Immediatelyfollowing,asolutionof6.5gof4-dimethylaminopyridine(DMAP)(54.5mmol,2.0eq)in80mLofdichloromethane(Note2)isaddedslowlyviaan18-gaugestainlessste
6、elcannula(Note5).Theinternaltemperatureisnotallowedtoriseabove72°Cduringthisaddition.Aceticanhydride(15.4mL,16.6g,163.2mmol,6.0eq)isthenaddeddropwiseviaaglasssyringeover5.5minataratetomaintaintheinternaltemperaturebelow72°C.Theresultantlightyellowsolutionisstirredat7
7、8°Cfor12hr(Note6).Duringthistime,thecolorofthesolutionintensifiesconsiderably.Thebrightyellowsolutioniswarmedto0°Cinanicewaterbathandstirredfor35min,duringwhichtimethecolorofthesolutionbecomesbrightyellow-orange.Thereactionisthenquenchedbythesequentialadditionof270mLofs
8、aturatedaqueousammoniumchlorideand200mLofsaturatedaqueoussodiumpotassiumtartrate.Theemulsionisremovedfromtheic
