Remarkably Stable Chiral Zirconium Complexes for Asymmetric Mannich-Type Reactions
作者:Kowichiro Saruhashi、Shū Kobayashi
DOI:10.1021/ja062776r
日期:2006.8.1
Isolable, air-stable, storable, and highly selective chiral zirconium catalysts for asymmetric Mannich-type reactions have been developed. The reactions of imines with silicon enolates proceeded smoothly using 1-10 mol % of the powdered zirconium catalyst to afford the corresponding adducts in high yields with high stereoselectivities. The catalyst could be recovered and reused without significant
已开发出用于不对称曼尼希型反应的可分离、空气稳定、可储存和高选择性手性锆催化剂。使用 1-10 mol% 的粉状锆催化剂,亚胺与硅烯醇化物的反应顺利进行,以高收率和高立体选择性提供相应的加合物。催化剂可以回收和再利用而不会显着损失活性。另一方面,获得了用于 X 射线分析的锆单晶,该晶体在不对称 Mannich 型反应中也表现出高性能。尽管这些锆催化剂的 NMR 分析显示在二氯甲烷中具有不同的结构,但表明不同催化剂形成了相同的关键中间体。
Highly selective enolization method for heteroatom substituted esters; its application to the ireland ester enolate claisen rearrangement
作者:Kouji Hattori、Hisashi Yamamoto
DOI:10.1016/s0040-4020(01)81109-1
日期:1994.3
A method for the stereoselective synthesis of silylketeneacetals from α-siloxy esters, β-hydroxy esters, and α-aminoesters is described. Internal quench with excess trimethylsilyl chloride of the lithium enolate at −100 °C, which is generated using a hindered base, LTMP, leads to the selective formation of E-silyl keteneacetal. In contrast, the deprotonation at −100 °C using LHMDS in THF-HMPA (4:1)
Highly selective generation and application of (E)- and (Z)-silyl ketene acetals from .alpha.-hydroxy esters
作者:Kouji Hattori、Hisashi Yamamoto
DOI:10.1021/jo00072a005
日期:1993.9
A method for the stereoselective synthesis of silyl ketene acetals from a-hydroxy esters is described. Internal quench with excess TMSCI of the lithium enolate at -100-degrees-C, which is generated using a hindered base, LTMP, leads to the selective formation of (E)-silyl ketene acetal. In contrast, the deprotonation at -100-degrees-C using LHMDS in THF-HMPA (4:1), followed by treatment with tert-butyldimethylsilyl chloride affords the (Z)-silyl ketene acetal selectively. The method can be applied to the stereoselective reaction of the Ireland ester enolate Claisen rearrangement and aldol synthesis.