4587-00-2Relevant articles and documents
Oxidative functional group transformations with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
Mizuno, Noritaka,Kamata, Keigo,Yamaguchi, Kazuya
scheme or table, p. 157 - 161 (2012/06/18)
A divanadium-substituted phosphotungstate TBA4[γ-PW 10O38V2(μ-OH)(μ-O)] (I, TBA = tetra-n-butylammonium) reacts with one equivalent H+ to form a bis-μ-hydroxo species [γ-PW10O38V 2(μ-OH)2]3- (I′) in organic media. The strong electrophilic oxidants such as [γ-PW10O 38V2(μ-OH)(μ-OOH)]3- (II) and [γ-PW10O38V2(μ-η2: η2-O2)]3- (III) are formed by the reaction of the bis-μ-hydroxo species with H2O2. In the presence of I and H+, H2O2-based oxidations such as (i) epoxidation of alkenes (17 examples including electron-deficient ones), (ii) hydroxylation of alkanes (11 examples), and (iii) oxidative bromination of alkenes, alkynes, and aromatics with Br- as a bromo source (12 examples including chlorination) chemo-, diastereo-, and regioselectively proceed to give the corresponding oxidized products in moderate to high yields with high efficiencies of H2O2 utilization.
Efficient epoxidation of electron-deficient alkenes with hydrogen peroxide catalyzed by [γ-PW10O38V2(μ-OH) 2]3-
Kamata, Keigo,Sugahara, Kosei,Yonehara, Kazuhiro,Ishimoto, Ryo,Mizuno, Noritaka
scheme or table, p. 7549 - 7559 (2011/08/03)
A divanadium-substituted phosphotungstate, [γ-PW10O 38V2(μ-OH)2]3- (I), showed the highest catalytic activity for the H2O2-based epoxidation of allyl acetate among vanadium and tungsten complexes with a turnover number of 210. In the presence of I, various kinds of electron-deficient alkenes with acetate, ether, carbonyl, and chloro groups at the allylic positions could chemoselectively be oxidized to the corresponding epoxides in high yields with only an equimolar amount of H2O2 with respect to the substrates. Even acrylonitrile and methacrylonitrile could be epoxidized without formation of the corresponding amides. In addition, I could rapidly (min) catalyze epoxidation of various kinds of terminal, internal, and cyclic alkenes with H;bsubesubbsubesub& under the stoichiometric conditions. The mechanistic, spectroscopic, and kinetic studies showed that the I-catalyzed epoxidation consists of the following three steps: 1) The reaction of I with H;bsubesubbsubesub& leads to reversible formation of a hydroperoxo species [I;circbsubesubbsubesubbsubesubcirccircbsupesup& (II), 2) the successive dehydration of II forms an active oxygen species with a peroxo group [ 2:2-O2)]3- (III), and 3) III reacts with alkene to form the corresponding epoxide. The kinetic studies showed that the present epoxidation proceeds via III. Catalytic activities of divanadium-substituted polyoxotungstates for epoxidation with H 2O2 were dependent on the different kinds of the heteroatoms (i.e., Si or P) in the catalyst and I was more active than [γ-SiW10O38V2(μ-OH)2] 4-. On the basis of the kinetic, spectroscopic, and computational results, including those of [γ-SiW10O38V 2(μ-OH)2]4-, the acidity of the hydroperoxo species in II would play an important role in the dehydration reactivity (i.e., k3). The largest k3 value of I leads to a significant increase in the catalytic activity of I under the more concentrated conditions. Copyright
Facial selectivity and stereospecificity in the (4 + 3) cycloaddition of epoxy enol silanes
Lo, Brian,Chiu, Pauline
supporting information; experimental part, p. 864 - 867 (2011/05/06)
The scope of the (4 + 3) cycloaddition using epoxy enol silanes has been examined. Unhindered and nucleophilic dienes react to give the highest yields, but hindered dienes give rise to higher diastereoselectivities. Notably, the cycloaddition shows facial
Homologation of vicinal polyketone networks to epoxy ketones with diazomethane
Hartung, Ryan E.,Paquette, Leo A.
, p. 23 - 26 (2007/10/03)
Admixture of vicinal di-, tri-, and tetraketones with ethereal diazomethane results in one-time methylene transfer to the less hindered face of the sterically most accessible and electron-deficient carbonyl group to deliver epoxy ketones in a highly selec
TRANSFORMATION OF ACETYLOXIRANES TO THIIRANE ANALOGS
Bubel, O. N.,Tishchenko, I. G.,Stasevich, G. Z.,Veraksich, E. L.,Filich, E. R.
, p. 1082 - 1085 (2007/10/02)
A method for the synthesis of acetylthiiranes was developed; this method includes the conversion of acetyloxiranes to diethylketals, dealkoxylation of the latter, replacement of the oxygen atom of the oxirane ring by sulfur, and acidic hydrolysis of the ethoxyvinylthiirane to acetylthiiranes.
Monoozonolysis of 2,3-Dimethylbutadiene in Pentane and in Methanol
Griesbaum, Karl,Keul, Helmut,Agarwal, Sudhir,Zwick, Gerhard
, p. 409 - 415 (2007/10/02)
2,3-Dimethylbutadiene (1) was attacked predominantly at only one double bond by a deficient amount of ozone in pentane or in methanol.In pentane, an α,β-unsaturated ozonide (4) was formed, which was further converted into an α,β-dibromoozonide (2) and into an α,β-epoxyozonide (6), respectively.Ozonolysis of 1 in methanol afforded an α,β-unsaturated methoxy hydroperoxide (8) and formaldehyde as well as a joint coproduct (9) of the latter two fragments.
SYNTHESIS OF 2-ALKYLTHIO-5-ACETYL-2-OXAZOLINES
Bubel', O.N.,Tishchenko, I.G.,Grinkevich, O.A.,Abramov, A.F.
, p. 352 - 355 (2007/10/02)
The reaction of 2-acetyloxiranes with alkyl thiocyanates in the presence of Lewis acids (BF3, AlCl3) has given 2-alkylthio-5-acetyl-2-oxazolines (yields 40-60percent).It has been shown that the reaction of trans-2-acetyl-3-methyloxirane and of trans-2-acetyl-3-methyloxirane and of trans-2-acetyl-2,3-dimethyloxirane with alkyl thiocyanates takes place stereospecifically and leads to cis-2-alkylthio-5-acetyl-2-oxazolines.
