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1、BRUI15-593_621r327-03-20032:51PMPage616616CHAPTER15Aromaticity•ReactionsofBenzeneBesidesavoidingcarbocationrearrangements,anotheradvantageofpreparingalkyl-substitutedbenzenesbyacylation–reductionratherthanbydirectalkylationisthatalargeexcessofbenzenedoesnothavet
2、obeused(Section15.14).Unlikealkyl-substitutedE.C.Clemmensen(1876–1941)benzenes,whicharemorereactivethanbenzene(Section16.3),acyl-substitutedbenzeneswasborninDenmarkandreceivedarelessreactivethanbenzene,sotheywillnotundergoadditionalFriedel–Craftsreactions.aPh.D.
3、fromtheUniversityofTherearemoregeneralmethodsavailabletoreduceaketonecarbonylgrouptoaCopenhagen.Hewasascientistmethylenegroup—methodsthatreduceallketonecarbonylgroups,notjustthosethatatClemmensenCorp.inNewark,areadjacenttobenzenerings.Twoofthemosteffectivearethe
4、Clemmensenreduc-NewYork.tionandtheWolff–Kishnerreduction.TheClemmensenreductionusesanacidicsolutionofzincdissolvedinmercuryasthereducingreagent.TheWolff–KishnerLudwigWolff(1857–1919)wasborninGermany.Hereceivedareductionemployshydrazine(H2NNH2)underbasiccondition
5、s.ThemechanismofPh.D.fromtheUniversityoftheWolff–KishnerreductionisshowninSection18.6.Strasbourg.HewasaprofessorattheCH2CH2CH3UniversityofJenainGermany.OZn(Hg),HCl,∆ClemmensenN.M.Kishner(1867–1935)wasCCH2CH3reductionborninMoscow.HereceivedaPh.D.fromtheUniversity
6、ofMoscowunderCH2CH2CH3thedirectionofMarkovnikov.HewasH2NNH2,HO−,∆aprofessorattheUniversityofWolff–KishnerTomskandlaterattheUniversityofreductionMoscow.Atthispoint,youmaywonderwhyitisnecessarytohavemorethanonewaytocarryoutthesamereaction.Alternativemethodsareusef
7、ulwhenthereisanotherfunc-tionalgroupinthemoleculethatcouldreactwiththereagentsyouareusingtocarryoutthedesiredreaction.Forexample,heatingthefollowingcompoundwithHCl(asrequiredbytheClemmensenreduction)wouldcausethealcoholtoundergosubstitu-tion(Section11.1).Underth
8、ebasicconditionsoftheWolff–Kishnerreduction,how-ever,thealcoholgroupwouldremainunchanged.CH2CH3Zn(Hg),HCl,∆OCCH3Cl−CH2CH3H2NNH2,HO,∆OHOHAlkylbenzeneswithstraight-chai
