An efficient ketone-catalyzed epoxidation using hydrogen peroxide as oxidant.
An efficient ketone-catalyzed epoxidation using hydrogen peroxide as oxidant.
复制标题
使用过氧化氢作为氧化剂的有效酮催化环氧化反应。
DOI：
10.1021/jo001180y
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Shi,Y
中科院分区：
文献类型：
--
作者：
Shu,L;Shi,Y
环氧化物是有机合成中非常重要的结构单元。1二环氧乙烷，无论是分离或原位生成，已被证明是非常通用的环氧化试剂。2-6在几乎每种情况下，二环氧乙烷的生成都使用过氧化单硫酸钾（KHSO 5）作为氧化剂（方案1）。7，8在我们最近使用果糖衍生的酮（1）进行不对称环氧化的研究期间，我们发现过氧化氢（H2 O2）可以与乙腈（eq 1）组合用作主要氧化剂。6l对于许多烯烃获得了高产率和ee。在该环氧化反应中，过氧化亚油酸2可能是形成二环氧乙烷（当量2）的活性氧化剂。9、10与使用过硫酸氢钾的方法相比，环氧化需要显著更少的溶剂和盐，沿着操作简单。为了进一步将该氧化剂体系（H_2O_2-CH_3CN）扩展到二环氧乙烷介导的环氧化反应中，我们测试了多种非手性酮作为可能的催化剂。在测试的那些中，发现三氟丙酮（CF 3COCH 3）是特别活性的催化剂。在此，我们希望报告我们最近在这方面的研究。
Epoxides are very important building blocks in organic synthesis. 1 Dioxiranes, either isolated or generated in situ, have been shown to be extremely versatile epoxidation reagents. 2-6 In nearly every case, the generation of dioxiranes uses potassium peroxomonosulfate (KHSO5) as oxidant (Scheme 1). 7, 8 During our recent study on asymmetric epoxidation using the fructose-derived ketone (1), we found that hydrogen peroxide (H2O2) could be used as primary oxidant in combination with acetonitrile (eq 1). 6l High yields and ee’s were obtained for a number of olefins. In this epoxidation, peroxyimidic acid 2 is likely to be the active oxidant for the formation of the dioxirane (eq 2). 9, 10 The epoxidation requires substantially less solvent and salts compared to the procedure using Oxone, along with being operationally simple. To further extend this oxidant system (H2O2-CH3CN) to the dioxiranemediated epoxidation, we have tested a variety of achiral ketones as possible catalysts. Among those tested, trifluoroacetone (CF3COCH3) was found to be a particularly active catalyst. Herein we wish to report our recent studies in this area.