Kurihara M, Miyata N
Kokuritsu Iyakuhin Shokuhin Eisei Kenkyusho Hokoku. 1998(116):63-8.
Dioxiranes have recently been shown to be important and versatile oxidants, which are generated from potassium monoperoxysulfate (KHSO5) and ketones. Dimethyldioxirane, a dioxirane generated from acetone as a ketone, is particularly useful as an oxidation reagent with a broad scope of synthetic applications. Several papers have been reported about stereoselective epoxidation using dimethyldioxirane. However, there have been only a few examples using dioxiranes generated from other ketones. Dioxiranes derived from sterically hindered ketones are expected to be "bulky oxidant", and to be useful for stereoselective epoxidation. In a CH2Cl2-buffered water (two-phase system) in the presence of phase-transfer agent under neutral condition (pH 7.8) according to the reported procedure, the epoxidations with hindered alpha-substituted cyclohexanones proceeded in very low yields. After a survey of possible conditions we found that basic (pH 11) CH2Cl2-MeOH-buffer system was effective for the epoxidations of olefins with Oxone (active constituent KHSO5) and substituted cyclohexanones. We carried out epoxidation of cyclohexen derivatives with dioxiranes derived from alpha-substituted cyclohexanones in a CH2Cl2-MeOH-buffer solvent system at pH 11. High trans selectivities were obtained. Furthermore, according to this method acyclic silyl ethers were stereoselectively oxidized to afford erythro epoxides.
最近研究表明，二氧杂环丙烷是一类重要且用途广泛的氧化剂，可由过一硫酸氢钾（KHSO5）和酮类生成。由丙酮作为酮生成的二甲基二氧杂环丙烷，作为一种具有广泛合成应用范围的氧化试剂，尤其有用。已有多篇关于使用二甲基二氧杂环丙烷进行立体选择性环氧化的论文报道。然而，使用由其他酮类生成的二氧杂环丙烷的例子却很少。源自空间位阻酮的二氧杂环丙烷有望成为“ bulky 氧化剂”，并可用于立体选择性环氧化。按照报道的方法，在中性条件（pH 7.8）下，于存在相转移剂的二氯甲烷 - 缓冲水（两相体系）中，用位阻α - 取代环己酮进行环氧化反应，产率极低。在研究了各种可能的条件后，我们发现碱性（pH 11）的二氯甲烷 - 甲醇 - 缓冲体系对于用 Oxone（活性成分 KHSO5）和取代环己酮对烯烃进行环氧化是有效的。我们在pH 11的二氯甲烷 - 甲醇 - 缓冲溶剂体系中，用源自α - 取代环己酮的二氧杂环丙烷对环己烯衍生物进行环氧化。获得了高反式选择性。此外，根据该方法，无环甲硅烷基醚被立体选择性氧化，得到赤式环氧化物。
