Catalytic Asymmetric Epoxidation of Aldehydes. Optimization, Mechanism, and Discovery of Stereoelectronic Control Involving a Combination of Anomeric and Cieplak Effects in Sulfur Ylide Epoxidations with Chiral 1,3-Oxathianes
作者:Varinder K. Aggarwal、J. Gair Ford、Sílvia Fonquerna、Harry Adams、Ray V. H. Jones、Robin Fieldhouse
DOI:10.1021/ja9812150
日期:1998.8.1
A range of 1,3-oxathianes based on camphorsulfonic acid have been prepared and tested in the catalytic asymmetric epoxidation of carbonyl compounds. It was found that the 1,3-oxathiane derived from acetaldehyde 5b gave the highest yield and enantioselectivity in the epoxidation process. The enantioselectivity was independent of the solvent and metal catalyst used (although yields were dependent on
已经制备了一系列基于樟脑磺酸的 1,3-氧杂环己烷并在羰基化合物的催化不对称环氧化中进行了测试。发现衍生自乙醛 5b 的 1,3-氧杂环己烷在环氧化过程中具有最高的产率和对映选择性。对映选择性与所使用的溶剂和金属催化剂无关(尽管产率取决于两者)。将最佳条件应用于一系列醛,并观察到良好的对映选择性和非对映选择性。探索了对映选择性的起源,特别是研究了 1,3-氧杂环己烷的氧的作用。因此,制备了基于樟脑磺酸的1,3-氧杂噻吩(衍生自甲醛)的硫和碳类似物(即,1,3-二噻烷和噻烷类似物)。使用这一系列类似物,空间效应被最小化,以便可以研究电子效应。该系列化合物在催化循环中与...