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1、控制因素StereoelectronicEffects-Theattackingelectrophilemustobeytheprincipleofmaximumoverlapoftheparticipatingorbitalsbyperpendicularapproachtotheplaneofatomswhichconstitutetheenolate(enol)function.C.StereoselectivityAlsoappliestoprotonationinreprotonationreaction:Nucle
2、ophilicadditiontocarbonylcompoundtakesplacenotat90°(perpendicular)butatanangleof105±5°DunitzTetrahedron1974,30,1563.StericEffectsii)DiastereoselectivityExocyclicEnolatesEndocyclicEnolatesiii)OtherConformationallyInflexibleSystemsiV)ConjugateAddition/Alkylation:Stere
3、ochemistryiii)AsymmetricAlkylationsConformationalorIntraannularChiralityTransfer§5-2AldolAddition(Condensation)§5-2-1基本反应1.名次术语syn/antiJ.Am.Chem.Soc.1981,103,2106.(supercedeserythro/threonomenclature)erythro/threoAngew.Chem.,Int.Ed.Eng.1980,19,557.SummaryAsymm.Synth
4、.Vol.3,pp.111-212.(Reviewofaldoldiastereoselection)IUPACPure.Appl.Chem.1976,45,11.OthersAngew.Chem.,Int.Ed.Eng.1966,5,385.(basedonCahn,Ingold,Prelog)Angew.Chem.,Int.Ed.Eng.1982,21,654.(Seebach,Prelog)J.Org.Chem.1982,47,3811.(Carey,Kuehne)§5-2-2立体化学A.非手性的醛与非手性烯醇盐Z-型烯
5、醇盐给出syn式为主的缩合产物(热力学产物)E-型烯醇盐给出anti式为主的缩合产物(动力学产物)syn:anti>98:2anti:syn92:8HeathcockJ.Org.Chem.1980,45,1066.-Zimmerman-TraxlerModel(J.Am.Chem.Soc.1957,79,1920)-Chair-like,closedtransitionstate:metalcoordinationtobothcarbonylsTransitionstateTransitionstateb.R1/R3增大，非对
6、映选择性提高(Syn选择性)R1c.金属离子也影响反应的非对映选择性，使用硼时选择性往往会变好，其原因可能是能形成更紧密的过渡态(B–O更短,R1/R3立体作用增大所致)。TetrahedronLett.1989,30,5681.J.Am.Chem.Soc.1973,95,3310.J.Org.Chem.1980,45,1066.MasamuneTetrahedronLett.1979,1665.d.当R2很大时，R3/R2立体作用比R1/R3作用可能会更强，有时会导致立体化学反转.e.Z-型烯醇盐得到的非对映选择性(fors
7、ynaldol)比E-型烯醇盐(foranti).>95:5f.立体化学的控制Z/E异构体的控制-利用羰基化合物或试剂结构的差异以及反应条件的不同Z-烯醇硼盐的制备E-烯醇硼盐的制备E-enolatesveryaccessibleusingtbutylthiolestersMasamuneTetrahedronLett.1979,2225.E-enolateMoreExamples与硼试剂结构及条件相关。BrownJ.Org.Chem.1992,57,499and2716.BrownJ.Org.Chem.1994,59,233
8、6.与底物结构及条件相关。BrownJ.Am.Chem.Soc.1989,111,3441.利用上述结果有时可实现立体化学的完全控制B.手性的醛与非手性烯醇盐的Aldol缩合a.FelkinAddition-Twofacesofaldehydearediastereotopi
