Concerning the Efficient Conversion of Epoxy Alcohols into Epoxy Ketones Using Dioxiranes
摘要:
Representative epoxy alcohols are cleanly converted into the corresponding epoxy ketones in high yield by selective oxidation using dimethyldioxirane (1a) and its trifluoro analogue (1b) under mild conditions. The oxidation is found to take place leaving the configuration at the epoxy functionality unaffected. The direct oxyfunctionalization of simple cyclic epoxides with the powerful dioxirane 1b provides another attractive method to access epoxy ketones regioselectively.
Concerning the Efficient Conversion of Epoxy Alcohols into Epoxy Ketones Using Dioxiranes
摘要:
Representative epoxy alcohols are cleanly converted into the corresponding epoxy ketones in high yield by selective oxidation using dimethyldioxirane (1a) and its trifluoro analogue (1b) under mild conditions. The oxidation is found to take place leaving the configuration at the epoxy functionality unaffected. The direct oxyfunctionalization of simple cyclic epoxides with the powerful dioxirane 1b provides another attractive method to access epoxy ketones regioselectively.
Good cis selectivity is observed in the epoxidation of the cyclic allylic alcohols 2-cyclopentenol and 2-cyclohexenol due to a hydroxy-directing effect through hydrogen bonding; however, for 2-cycloheptenol and 2-cyclooctenol hydrogen bonding is ineffective and steric interactions cause a higher trans selectivity. The conformationally fixed cis- and trans-5-tert-butyl-2-cyclohexenols serve as suitable
A versatile method for preparation of O-alkylperoxycarbonic acids: epoxidation with alkyloxycarbonylimidazoles and hydrogen peroxide
作者:Youko Tsunokawa、Shigeo Iwasaki、Shigenobu Okuda
DOI:10.1016/s0040-4039(00)87275-5
日期:1982.1
A variety of O-alkylperoxycarbonic acids () were conveniently prepared by utilizing alkyloxycarbonylimidazoles () as their precursors. Epoxidation of alkenes with such peroxy-acids was studied and their reactivities were compared with those of peroxycarboxylicacids.
A Highly Chemoselective, Diastereoselective, and Regioselective Epoxidation of Chiral Allylic Alcohols with Hydrogen Peroxide, Catalyzed by Sandwich-Type Polyoxometalates: Enhancement of Reactivity and Control of Selectivity by the Hydroxy Group through Metal−Alcoholate Bonding
作者:Waldemar Adam、Paul L. Alsters、Ronny Neumann、Chantu R. Saha-Möller、Dorit Sloboda-Rozner、Rui Zhang
DOI:10.1021/jo0266386
日期:2003.3.1
Sandwich-type polyoxometalates (POMs), namely [WZnM2(ZnW9O34)2]q- [M = Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], are shown to catalyze selectively the epoxidation of chiral allylicalcohols with 30% hydrogen peroxide under mild conditions (ca. 20 degrees C) in an aqueous/organic biphasic system. The transition metals M in the central ring of polyoxometalate do not affect the reactivity
Eu(OTf)<sub>3</sub>-Catalyzed Highly Regioselective Nucleophilic Ring Opening of 2,3-Epoxy Alcohols: An Efficient Entry to 3-Substituted 1,2-Diol Derivatives
In our study of the totalsynthesis of (+)-irciniastatin A, we found a need to develop a method that enables a C3-selective nucleophilicringopening of 2,3-epoxyalcohol by MeOH, by which we found that the use of combined catalytic amounts of Eu(OTf)3 and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) enables the intended transformation to obtain 3-methoxy-1,2-diol efficiently. Promising features of a
intermediates I and II. Whereas intermediate II is responsible for the competitive formation of elemental sulfur, intermediate I, presumably an oxathiirane, is the active sulfur-transferring species. The episulfidation was compared with the epoxidation by the related dimethyldioxirane, and bo...
噻吩内过氧化物 2 是通过噻吩 1 的光氧化制备的,当在环烯烃存在下热解时,将硫原子(高达 92%)转移到应变的环烯烃以形成硫杂丙烷。非对映异构体对顺式/反式环辛烯 (5b) 进行立体选择性反应,这说明了协调过程,而不是开放的偶极和/或双自由基中间体。还研究了手性环辛烯醇 5c-e 组,并通过化学相关性和 NMR 光谱和 X 射线分析指定了各个硫杂丙环的相对构型。该过程的一级动力学清楚地表明内过氧化物 2 本身不是硫转移物质,但它被热转化为中间体 I 和 II。而中间体 II 负责元素硫的竞争性形成,中间体 I,大概是氧杂硫杂,是活性硫转移物质。将环硫化与相关二甲基二环氧乙烷的环氧化进行了比较,并...