The exceptional chelating ability of dimethylaluminum chloride and methylaluminum dichloride.: The merged stereochemical impact of α- and β-stereocenters in chelate-controlled carbonyl addition reactions with enolsilane and hydride nucleophiles
The exceptional chelating ability of dimethylaluminum chloride and methylaluminum dichloride.: The merged stereochemical impact of α- and β-stereocenters in chelate-controlled carbonyl addition reactions with enolsilane and hydride nucleophiles
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DOI：
10.1021/ja011337j
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发表时间：
2001-11-07
影响因子：
15
通讯作者：
Masse, CE
中科院分区：
文献类型：
--
作者：
Evans, DA;Allison, BD;Masse, CE
系统地研究了非手性未取代烯烯硅烷和手性-羟基醛在有利于螯合控制的条件下，Lewis酸促进（Mukaiyama）醛醇反应的立体选择性。对-烷氧基醛和-硅氧基醛仅含-或-中心的烯醇化硅烷醛反应可实现良好的立体控制。对-二取代醛的螯合中间体的检查得出结论，合成醛非对映体具有立体中心的排列，其中-和-取代基在醛羰基上赋予强化的面偏置。因此，观察到合成醛的醛醇反应具有均匀优异的非对映面选择性。在-和-位置含有相反立体控制元素的相应抗醛反应表现出可变和不可预测的选择性。
A systematic investigation of the stereoselectivity in Lewis acid-promoted (Mukaiyama) aldol reactions of achiral unsubstituted enolsilanes and chiral beta -hydroxy aldehydes proceeding under conditions favoring chelation control is presented. Good stereocontrol can be realized for enolsilane aldol reactions of beta -alkoxy and beta -silyloxy aldehydes bearing only an alpha- or a beta -stereogenic center. Examination of the chelated intermediates for alpha,beta -disubstituted aldehydes concludes that the syn aldehyde diastereomer possesses the arrangement of stereocenters wherein the alpha- and beta -substituents impart a reinforcing facial bias upon the aldehyde carbonyl. Aldol reactions of syn aldehydes were thus observed to proceed with uniformly excellent diastereofacial selectivity. Aldol reactions of the corresponding anti aldehydes containing opposing stereocontrol elements at the alpha- and beta -positions exhibit variable and unpredictable selectivity.