Catalytic Asymmetric Simmons−Smith Cyclopropanation of Silyl Enol Ethers. Efficient Synthesis of Optically Active Cyclopropanol Derivatives
作者:Haifeng Du、Jiang Long、Yian Shi
DOI:10.1021/ol0609659
日期:2006.6.1
[reaction: see text] This paper describes a catalytic asymmetric Simmons-Smith cyclopropanation of silyl enol ethers using dipeptide 2 as the ligand. A variety of optically active cyclopropyl silyl ethers can be obtained in high yields. Up to 96% ee was obtained. The dipeptide can be recovered after the reaction in good yield and reused without the loss of reactivity or enantioselectivity.
Rhodium-Catalyzed Enantioselective Vinylogous Addition of Enol Ethers to Vinyldiazoacetates
作者:Austin G. Smith、Huw M. L. Davies
DOI:10.1021/ja3092399
日期:2012.11.7
A highly asymmetric vinylogous addition of acyclic silyl enolethers to siloxyvinyldiazoacetate is described. The reaction features a diastereoselective 1,4-siloxy group migration event. Products are obtained in up to 97% ee. When more sterically crowded silyl enolethers are employed, an enantioselective formal [3+2] cycloaddition becomes the dominant reaction pathway. Control experiments reveal the
描述了无环甲硅烷基烯醇醚与甲硅烷氧基乙烯基重氮乙酸酯的高度不对称乙烯基加成。该反应具有非对映选择性 1,4-甲硅烷氧基迁移事件。产品的 ee 高达 97%。当使用空间上更拥挤的甲硅烷基烯醇醚时,对映选择性形式的 [3+2] 环加成成为主要的反应途径。对照实验表明 (Z)-烯烃几何结构对于高水平的对映控制至关重要。