Lewis base catalyzed aldol additions of chiral trichlorosilyl enolates and silyl enol ethers
Lewis base catalyzed aldol additions of chiral trichlorosilyl enolates and silyl enol ethers
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DOI：
10.1021/jo051930
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发表时间：
2005-12-23
影响因子：
3.6
通讯作者：
Pham, SM
中科院分区：
文献类型：
--
作者：
Denmark, SE;Fujimori, S;Pham, SM
研究了由乳酸、3-羟基异丁酸酯和3-羟基丁酸酯衍生的手性烯氧基硅烷催化的手性Lewis碱催化的羟醛加成反应中双非对映异构体的结果。由手性甲基酮和乙基酮衍生的三氯硅烯醇类化合物在磷酰胺存在下发生缩醛反应，研究了这些烯醇类化合物的本征选择性和手性催化剂的外立体诱导作用。在与乳酸衍生的烯醇酸酯的反应中，强烈的内部立体诱导主导了羟醛加成的立体化学结果。对于3-羟基异丁酸酯和3-羟基丁酸酯衍生的烯醇酸酯，观察到了催化剂控制的非对映选择性，而残留的立体中心对反应的影响很小。将相应的三甲基硅烯醇醚用于SiCl4/双磷酰胺催化的Aldol加成反应，并考察了双非对映反应的影响。该工艺的整体非对映选择性再次受到催化剂强烈的外部影响的控制。
The consequences of double diastereodifferentiation in chiral Lewis base catalyzed aldol additions using chiral enoxysilanes derived from lactate, 3-hydroxyisobutyrate, and 3-hydroxybutyrate have been investigated. Trichlorosilyl enolates derived from the chiral methyl and ethyl ketones were subjected to aldolization in the presence of phosphoramides, and the intrinsic selectivity of these enolates and the external stereoinduction from chiral catalyst were studied. In the reactions with the lactate derived enolate, the strong internal stereoinduction dominated the stereochemical outcome of the aldol addition. For the 3-hydroxyisobutyrate- and 3-hydroxybutyrate derived enolates, the catalyst-controlled diastereoselectivities were observed, and the resident stereogenic centers exerted marginal influence. The corresponding trimethylsilyl enol ethers were employed in SiCl4/bisphosphoramide catalyzed aldol additions, and the effect of double diastereodifferentiation was also investigated. The overall diastereoselection of the process was again controlled by the strong external influence of the catalyst.