第9章 醚

第九章醚主要内容醚的制备（Williamson醚合成法，烯烃的烷氧汞化－脱汞反应）醚类的化学性质，酸性条件下C－O键的开裂环氧乙烷衍生物的酸性和碱性开环冠醚及其性质和应用一、醚的结构、分类及命名饱和醚烯基醚芳基醚饱和醚环醚大环多醚冠醚ROR'sp2杂化ROR'ROR'（R=烷基）CHORArOR(CH2)nOOOOOOOR'R1、结构与命名2、命名3－甲氧基－1,2－丙二醇OCH3OCH3H3COHOCH2OHOCH3CHCH2CH2CH2苯甲醚乙二醇二甲醚丙三醇－1－甲醚1,2－二甲氧基乙烷甲氧基苯anisole1,2-dimethoxyethane3-methoxypropane-1,2-diolCH3CH2OCH2CH3CH3COCH2CH3CH3CH3CH2CHOH3C乙醚（二乙基醚）乙基叔丁基醚甲基乙烯基醚对称醚diethyletherethylt-butylethermethylvinylether环氧乙烷反－2,3－环氧丁烷1,2－环氧丙烷oxirane2－甲基环氧乙烷2-methyloxiranetrans-2,3-dimethyloxirane反－2,3－二甲基环氧乙烷OH2CCH2OH2CCHCH3OCH3H3CHH1231231,3－环氧丙烷氧杂环丁烷对二氧六环1,4－二氧六环四氢呋喃THF二氢吡喃DHPoxetane1,4-dioxanetetrahydrofuran3,4-dihydro-2H-pyranOOOOO412365二、醚的制法1、Williamson醚合成法（制备醚的主要方法）ROR'RONaLR'+NaL+SN2•1oR’－L较好；3oR’－L消除为主。例：CH3COCH2CH3CH3CH3CH3CONaCH3CH3XCH2CH3+OHCH3OTs+NaOHOCH3芳基醚CCH2ClClCH2CH2OHCH2ClNaOHCCH2ClClCH2O四元环醚L=X,TsO2、醇脱水制备对称醚局限性•只适合1o醇制备对称醚，不适合制备非对称醚•SN1或SN2机理，有消除、重排等副产物OHR2H+ROR+H2OOOHHO+H2OH2SO4HOOH2H2SO4OO+H2O2例3、烯烃与醇反应制备叔烷基醚•合成上的应用：保护醇羟基CH2CRR'HOR+HClCH3CRR'ORHOBrHO例：完成转变HOBrH2CCH3CH3H2SO4OBrCCH3H3CCH3NaCCHOCCH3H3CCH3H+H2OHO合成路线4、烯烃的烷氧汞化——还原（脱汞）反应(Alkoxymercuration-Demercuration)复习：烯烃的羟汞化－还原（脱汞）机理：CHCH2RH2O,THFCHCH3ROHHg+Hg(OAc)2NaBH4H2OOHHOROR？CHCH2RHgOAcOAcCHCH2RHgOAcH2OCHCH2RHgOAcHO-H+CHCH2RHgOAcHOHCHCH2RHgHHOCHCH3RHOHg+NaBH4烯烃的烷氧汞化——还原（脱汞）反应醚CHCH2RR'OHCHCH3ROR'Hg(OCCF3)2NaBH4O炔烃的烷氧汞化——还原反应制备烯基醚CCHRR'OHCCH2ROR'Hg++NaBH4烯基醚•比较：炔烃的水合反应CCHRCCH2ROHHgSO4H2OCCH3RO烯醇三、醚类的化学性质结构特点分析C上连有氧，H易被氧化a碳有亲电性，但难亲核取代a碳有亲电性，可亲核取代较好的离去基氧有碱性，可与酸结合CORR'HH+CHORR'H醚在中性、碱性和弱酸性条件下稳定，常用作溶剂1、醚的自氧化（a-氢的氧化）提示：醚类试剂（乙醚、THF等）久置使用时要当心•先用淀粉－KI（2％的醋酸溶液）试验•蒸馏时勿蒸干•可用还原剂处理除去过氧化物（如FeSO4，LiAlH4，Na等）CORR'HHO2（空气）CORR'HOOH2、醚键氧的碱性ROR'HClROR'HOOBH3MgRXEtOEtEtOEtBH3Cl+ROR'H2SO4ROR'H+HSO4+Brönsted碱Lewis碱Oxoniumsalt3、醚键的开裂（醚在酸性体系中的亲核取代）醚键在中性、碱性或弱酸性条件下不会断裂。H+ROR'HNuRNu+HOR'ROR'•分析：弱酸性条件下可离去，离去能力比H2O差(亲核能力弱及浓度稀时)难进行ROR'NuRNu+OR'SN2•分析：中性、碱性条件下差离去基难进行醚键可被HI和HBr在加热下断裂ROR'HXRXHOR'+X=I,Br例：HX过量时，生成2分子卤代烷H3CCHH3COCHCH3CH3H3CCHH3CIO48%HBr(过量)OHBrBrBr+H3CCHH3COHH3CCHH3CIHIHI（过量）2过量HBr过量不对称醚醚键的开裂取向基团体积差别不大小小小较大大很大如何解释以上反应取向？1o2o3o手性碳构型保持CH3CH2OCH2CH2CH3CH3CH2OHICH2CH2CH3+CH3CH2IHOCH2CH2CH3+HICH3OCH2CH2CH3HICH3IHOCH2CH2CH3+CH3OCCH3CH3HICH3OH+CH3OC2H5CH3HHICH3I+HOC2H5CH3HCH3ICCH3CH3CH3醚键开裂机理（亲核取代反应机理）•SN2机理HICH3OCH3CH3HCH3OCH3CH3HHICH3I+HOCH3CH3HSN2，位阻影响为主SN2ICCH3CH3CH3CH3OCCH3CH3CH3CH3OCCH3CH3CH3HICH3OH+CCH3CH3CH3IHI•SN1机理SN1，中间体稳定性为主SN1•叔丁基醚两类较易水解的醚类化合物用于醇的保护和脱保护ROCCH3CH3ROH+CH3CH3CH3CCH2H2O/H+•烯基醚(了解)H2O/H+CCHR'RORCHCHR'RO+HOR总是在烯基醚键处开裂醛（或酮）醇用一般的醚水解机理能解释吗？CCHR'ROROH2HCHCR'RORHCHCR'RORHH2OCHCR'RORHOH2CHCR'RORHOHHCHCR'RORHOHH+CHCR'RHOH-ORH+烯基醚水解机理亲电加成半缩醛（质子化）消除四、1,2－环氧化合物（Epoxides）OHH免疫抑制剂OOOOOHOH雷公藤内酯醇(-)-Triptolide(7R,8S)-DisparlureGypsymothpheromone雌舞毒蛾引诱剂OCC1,2－环氧化合物EpoxidesOxiranes（IUPAC）1、1,2－环氧化合物的制备分子内SN2立体专一OHOClHOHHOHClHOHOOH注意下列两立体异构体反应的区别transcis提示：R2R1R3R4PhCO3HR2R1R3R4HOXOHR2R1R3R4OSharpless不对称环氧化反应（1980）（了解）e.e.90%()-酒石酸二乙酯()-diethyltartarate(-)-酒石酸二乙酯(-)-diethyltartarateR3OHt-BuOOH,Ti(O-iPr)4()-diethyltartarateCH2Cl2,-20oCR2R1R3OHR2R1OR3OHR2R1Ot-BuOOH,Ti(O-iPr)4(-)-diethyltartarateCH2Cl2,-20oCCOOEtHHOCOOEtOHHCOOEtHOHCOOEtHOHTheNobelPrizeinChemistry2001WilliamS.KnowlesRyojiNoyoriK.BarrySharplessfortheirworkonchirallycatalysedhydrogenationreactionsforhisworkonchirallycatalysedoxidationreactions2、1,2－环氧化合物的酸性开环•反应取向：在取代基多的一端开环•立体化学：反式开环ORHH+ORHHNuNuOHRH酸性开环机理与质子结合，亲电性增强ORHOH+R'OHH+HXHCNHOHRHR'OOHRHXOHRHCNOHRHH2O（弱亲核试剂）3、碱性开环（亲核试剂亲核能力较强）ORHOR'O1.R'MgXHOHRHOHHOOR'RH2.H2OHOR'RHR'NH2HONHR'RH1.LiAlH42.H2OHOCH3RH,H2O,HOR'ORHNuORHNuOHRHNuHS碱性开环机理•反应取向：在取代基少的一端开环•立体化学：反式开环位阻小有利（溶剂）例：1,2－环氧化合物的酸性或碱性开环OH3CH3CCH3HCH3ONaCH3OHHOH3CH3CCH3HOCH3H2SO4CH3OHOHH3CH3CCH3HH3COOH3CH3CC2H5HNHHOH3CH3CC2H5HNOt-BuNaOHH2OH2SO4H2OOHt-BuOHOHt-BuOH五、冠醚（CrownEthers）12-冠-415-冠-518-冠-612-Crown-415-Crown-518-Crown-6OOOOOOOOOOOOOOOCrown18-Crown-6OOOOOO1、冠醚的制备OOOHOH+OOClClKOHOOOOOO18-冠-6Williamson醚合成法OHOHClOCl+NaOHOOOOOO二苯并-18-冠-6C.J.Pederson,1960s2、冠醚对金属离子的络合冠醚的作用络合正离子，使负离子“裸露”相转移催化剂KMnO418-Crown-6室温，快~100％COOHCOOH合成上的应用举例MnO4-OOOOOOOOOOOOOOOLi+Na+K+CharlesJ.Pedersen(1904~1989)DonaldJ.Cram(1919~2001)Jean-MarieLehn(1939~)TheNobelPrizeinChemistry1987fortheirdevelopmentanduseofmoleculeswithstructure-specificinteractionsofhighselectivity提出“主客体化学”概念“host-guestchemistry”提出“超分子化学”概念“supramolecular”发现了冠醚本次课小结醚的制备（Williamson醚合成法，烯烃的烷氧汞化－脱汞反应）醚类的化学性质（O的碱性，自氧化，酸性条件下C－O键的开裂）环氧乙烷衍生物的酸性和碱性开环（开环取向及立体化学）冠醚及其性质和应用