路易斯酸的路易斯碱活化。硅基烯酮缩醛与醛的加成反应。

Lewis base activation of lewis acids. Addition of silyl ketene acetals to aldehydes.

作者信息

Denmark Scott E, Wynn Thomas, Beutner Gregory L

机构信息

Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana 61801, USA.

出版信息

J Am Chem Soc. 2002 Nov 13;124(45):13405-7. doi: 10.1021/ja0282947.

DOI:10.1021/ja0282947

PMID:12418891

Abstract

The weak Lewis acid silicon tetrachloride can be activated by catalytic amounts of the chiral bisphosphoramide (R,R)-3 to form a highly reactive, chiral trichlorosilyl cation which is an extremely effective promoter of aldol addition reactions between aldehydes and silyl ketene acetals. The tert-butyldimethylsilyl ketene acetal of methyl acetate adds nearly instantaneously to aromatic and olefinic aldehydes as well as aliphatic aldehydes (albeit more slowly) with excellent enantioselectivity. The homologous tert-butyldimethylsilyl ketene acetal of tert-butyl propanoate adds with nearly exclusive anti diastereoselectivity to a similar range of aldehydes also with excellent enantioselectivity. The origin of the slower reaction rate with aliphatic aldehydes is revealed to be the formation of chlorosilyl ether adducts.

摘要

弱路易斯酸四氯化硅可通过催化量的手性双磷酰胺（R，R）-3活化，形成高活性的手性三氯甲硅烷基阳离子，该阳离子是醛与硅基烯酮缩醛之间羟醛加成反应的极其有效的促进剂。乙酸甲酯的叔丁基二甲基硅基烯酮缩醛几乎能瞬间加成到芳香醛、烯醛以及脂肪醛上（尽管速度较慢），对映选择性极佳。丙酸叔丁酯的同系叔丁基二甲基硅基烯酮缩醛以几乎完全的反式非对映选择性加成到类似范围的醛上，对映选择性也极佳。脂肪醛反应速率较慢的原因是形成了氯硅烷基醚加合物。