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1、14.1114.11 Alkane Synthesis Using Alkane Synthesis Using Organocopper ReagentsOrganocopper ReagentsLithium dialkylcuprates are useful synthetic Lithium dialkylcuprates are useful synthetic reagents.reagents.They are prepared from alkyllithiums and a They are prepared from alkyllithiums and a copper(
2、I) halide.copper(I) halide.2RLi + 2RLi + CuCuX XR R2 2CuCuLi + LiLi + LiX Xcustomary solvents are diethyl ether and customary solvents are diethyl ether and tetrahydrofuran (THF)tetrahydrofuran (THF)Lithium DialkylcupratesLithium Dialkylcupratesthe alkyllithium first reacts with the copper(I) the al
3、kyllithium first reacts with the copper(I) halidehalideHow?How?R RLiLiCuCuI ILiLi+ +R RCuCuI I the alkyllithium first reacts with the copper(I) the alkyllithium first reacts with the copper(I) halidehalidethen a second molecule of the alkyllithium then a second molecule of the alkyllithium reacts wi
4、th the alkylcopper species formed in reacts with the alkylcopper species formed in the first stepthe first stepLiLi+ + How?How?R RLiLiCuCuI ILiLi+ +R RCuCuI I R RLiLiR RCuCuR RCuCuR RR R2 2CuCuLiLi + +RRX XR RRR+ + R RCuCu + + LiLiX XArAr2 2CuCuLiLi + +RRX XArArRR + + ArArCuCu + + LiLiX XLithium dio
5、rganocuprates are used toLithium diorganocuprates are used to form CC bondsform CC bondsprimary alkyl halides work best (secondary and primary alkyl halides work best (secondary and tertiary alkyl halides undergo elimination)tertiary alkyl halides undergo elimination)diethyl etherdiethyl ether(CH(CH
6、3 3) )2 2CuCuLiLi + +CHCH3 3(CH(CH2 2) )8 8CHCH2 2I ICHCH3 3(CH(CH2 2) )8 8CHCH2 2CHCH3 3(90%)(90%)Example: Lithium Example: Lithium dimethyldimethylcupratecuprateExample: Lithium Example: Lithium diphenyldiphenylcupratecupratediethyl etherdiethyl ether(C(C6 6H H5 5) )2 2CuCuLiLi+ +CHCH3 3(CH(CH2 2)
7、 )6 6CHCH2 2I ICHCH3 3(CH(CH2 2) )6 6CHCH2 2C C6 6H H5 5(99%)(99%)( (CHCH3 3CHCH2 2CHCH2 2CHCH2 2) )2 2CuLiCuLiVinylic halides can be usedVinylic halides can be used+ +diethyl etherdiethyl etherBrBrCHCH2 2CHCH2 2CHCH2 2CHCH3 3(80%)(80%)( (CHCH3 3CHCH2 2CHCH2 2CHCH2 2) )2 2CuLiCuLiAryl halides can be
8、 usedAryl halides can be used+ +diethyl etherdiethyl etherI ICHCH2 2CHCH2 2CHCH2 2CHCH3 3(75%)(75%)14.1214.12 An Organozinc Reagent An Organozinc Reagent forfor Cyclopropane SynthesisCyclopropane SynthesisIodomethylzinc iodideIodomethylzinc iodidereacts with alkenes to form cyclopropanesreacts with
9、alkenes to form cyclopropanes reaction with alkenes is called thereaction with alkenes is called the Simmons-Smith reactionSimmons-Smith reactionCHCH2 2I I2 2+ Zn + ZnICHICH2 2ZnIZnICuCuformed by reaction of diiodomethane withformed by reaction of diiodomethane with zinc that has been coated with co
10、pperzinc that has been coated with copper (called zinc-copper couple)(called zinc-copper couple)diethyl etherdiethyl etherExampleExampleH H2 2C CC CCHCH2 2CHCH3 3CHCH3 3CHCH2 2I I2 2, Zn/Cu, Zn/CuCHCH2 2CHCH3 3CHCH3 3(79%)(79%)Stereospecific syn-additionStereospecific syn-additiondiethyl etherdiethy
11、l etherCHCH2 2I I2 2, Zn/Cu, Zn/CuC CC CCHCH3 3CHCH2 2CHCH2 2CHCH3 3H HH HCHCH3 3CHCH2 2CHCH2 2CHCH3 3H HH HStereospecific syn-additionStereospecific syn-additiondiethyl etherdiethyl etherCHCH2 2I I2 2, Zn/Cu, Zn/CuC CC CCHCH3 3CHCH2 2CHCH2 2CHCH3 3H HH HCHCH3 3CHCH2 2CHCH2 2CHCH3 3H HH H14.1314.13
12、Carbenes and CarbenoidsCarbenes and CarbenoidsCarbeneCarbenename to give to species that contains aname to give to species that contains a divalent carbon (carbon with two bondsdivalent carbon (carbon with two bonds and six electrons)and six electrons)C C BrBrBrBrdibromocarbenedibromocarbeneCarbenes
13、 are very reactive; normally cannot Carbenes are very reactive; normally cannot be isolated and stored.be isolated and stored. Are intermediates in certain reactions.Are intermediates in certain reactions.Generation of DibromocarbeneGeneration of DibromocarbeneC CBrBrBrBrBrBrH H+ +OC(CHOC(CH3 3) )3
14、3 H H+ +OC(CHOC(CH3 3) )3 3 C CBrBrBrBrBrBr Generation of DibromocarbeneGeneration of Dibromocarbene+ +C CBrBrBrBrBrBr C C BrBrBrBrBrBr Carbenes react with alkenesCarbenes react with alkenes to give cyclopropanesto give cyclopropanes+ CHBr+ CHBr3 3BrBrBrBr(75%)(75%)CBrCBr2 2is an intermediate is an
15、intermediate stereospecific syn additionstereospecific syn additionKOC(CHKOC(CH3 3) )3 3(CH(CH3 3) )3 3COHCOH14.1414.14 Transition-Metal Organic CompoundsTransition-Metal Organic CompoundsIntroductionIntroductionMany organometallic compounds derivedMany organometallic compounds derived from transiti
16、on metals have useful properties.from transition metals have useful properties. Typical transition metals are iron, nickel,Typical transition metals are iron, nickel, chromium, platinum, and rhodium.chromium, platinum, and rhodium.18-Electron Rule18-Electron RuleThe number of ligands attached to a metalThe number of ligands attached to a metal will be such that the sum of the elec
