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1、8ReactionsInvolvingTransitionMetalsIntroductionInthischapterwediscussimportantsyntheticreactionsthatinvolvetransitionmetalcompoundsandintermediates.Reactionsinvolvingcopperandpalladium,thetransitionmetalsthathavethewidestapplicationsinsynthesis,arediscussedinthefirsttwosections
2、.Inthethirdsection,weconsiderseveralothertransitionmetals,includingnickel,rhodium,andcobalt.Incontrasttolithium,magnesium,andzinc,wheretheorganometallicreagentsareusedinstoichiometricquantities,manyofthetransitionmetalreactionsarecatalyticprocesses.Themechanismsaredescribedinte
3、rmsofcatalyticcyclesthatshowtheroleofthecatalyticspeciesinthereactionanditsregeneration.Anotherdistinguishingfeatureoftransitionmetalreactionsisthattheyfrequentlyinvolvechangesinoxidationstateatthemetalatom.Inthefinaltwosectionswedealwithtransitionmetal–catalyzedalkeneexchange(
4、metathesis)reactionsandorganometalliccompoundsthatfeaturebondingoftheorganiccomponent.8.1.OrganocopperIntermediates8.1.1.PreparationandStructureofOrganocopperReagentsThesyntheticapplicationoforganocoppercompoundsreceivedamajorimpetusfromthestudyofthecatalyticeffectofcoppersalt
5、sonreactionsofGrignardreagentswith-unsaturatedketones.1AlthoughGrignardreagentsnormallyaddtosuchcompoundstogivethe1,2-additionproduct,thepresenceofcatalyticamountsofCu(I)resultsinconjugateaddition.Mechanisticstudypointedtoaveryfastreactionbyanorganocopperintermediate.1H.O.H
6、ouse,W.L.Respess,andG.M.Whitesides,J.Org.Chem.,31,3128(1966).675676H2OCH3MgBrH+CH3CHCHC(CH3)2CHAPTER8OOHReactionsInvolvingTransitionMetalsCH3CHCHCCH3Cul,CH3MgBrH2O(CH3)2CHCH2CCH3H+OSubsequently,muchofthedevelopmentoforganocopperchemistryfocusedonstoichiometricreagentspreparedfr
7、omorganolithiumcompounds.Severaltypesoforganometalliccompoundscanresultfromreactionsoforganolithiumreagentswithcopper(I)salts.2Metal-metalexchangereactionsusinga1:1ratiooflithiumreagentandacopper(I)saltgivealkylcoppercompoundsthattendtobepolymericandarelessusefulinsynthesisthan
8、the2:1or3:1“ate”compounds.+Li+RLi+Cu(I)[RCu]n+2RLi+Cu(
