51646-05-0Relevant articles and documents
A study of the epoxidation of cycloolefins by the t-buoh copper-permanganate system
Baqi, Younis,Giroux, Simon,Corey
, p. 959 - 961 (2009)
Evidence is presented that Cu(MnO4)2 effectively epoxidizes trisubstituted steroid olefins by a nonconcerted pathway.
Bimetallic Radical Redox-Relay Catalysis for the Isomerization of Epoxides to Allylic Alcohols
Ye, Ke-Yin,Mccallum, Terry,Lin, Song
supporting information, (2019/06/24)
Organic radicals are generally short-lived intermediates with exceptionally high reactivity. Strategically, achieving synthetically useful transformations mediated by organic radicals requires both efficient initiation and selective termination events. Here, we report a new catalytic strategy, namely, bimetallic radical redox-relay, in the regio- and stereoselective rearrangement of epoxides to allylic alcohols. This approach exploits the rich redox chemistry of Ti and Co complexes and merges reductive epoxide ring opening (initiation) with hydrogen atom transfer (termination). Critically, upon effecting key bond-forming and -breaking events, Ti and Co catalysts undergo proton transfer/electron transfer with one another to achieve turnover, thus constituting a truly synergistic dual catalytic system.
Biosynthesis of 20-hydroxyecdysone in plants: 3β-Hydroxy-5β-cholestan-6-one as an intermediate immediately after cholesterol in Ajuga hairy roots
Fujimoto, Yoshinori,Maeda, Izumi,Ohyama, Kiyoshi,Hikiba, Juri,Kataoka, Hiroshi
, p. 59 - 64 (2015/02/19)
3β-Hydroxy-5β-cholestan-6-one was identified in the EtOAc extract of Ajuga hairy roots by micro-analysis using LC-MS/MS in the multiple reaction mode (MRM). Furthermore, administration of (2,2,4,4,7,7-2H6)- and (2,2,4,4,6,7,7-2H7)-cholesterols to the hairy roots followed by LC-MS/MS analysis of the EtOAc extract of the hairy roots indicated that cholesterol was converted to the 5β-ketone with hydrogen migration from the C-6 to the C-5 position. These findings, in conjunction with the previous observation that the ketone was efficiently converted to 20-hydroxyecdysone, strongly suggest that the 5β-ketone is an intermediate immediately formed after cholesterol during 20-hydroxyecdysone biosynthesis in Ajuga sp. In addition, the mechanism of the 5β-ketone formation from cholesterol is discussed.
Rhodium acetate-catalyzed aerobic Mukaiyama epoxidation of alkenes
Shabashov, Dmitry,Doyle, Michael P.
supporting information, p. 10009 - 10013 (2013/11/06)
Mukaiyama epoxidation of alkenes under oxygen catalyzed by rhodium acetate with isobutyraldehyde as the reducing agent is as or more effective than previously reported procedures. A variety of alkenes, including terpenes and cholesterol derivatives, were oxidized. And high regioselectivity for monoepoxidation was observed with neryl, geranyl, and linalyl acetates.
Surface functionalization of supported Mn clusters to produce robust Mn catalysts for selective epoxidation
Muratsugu, Satoshi,Weng, Zhihuan,Tada, Mizuki
, p. 2020 - 2030 (2013/09/24)
A robust heterogeneous Mn catalyst for selective epoxidation was prepared by the attachment of a Mn4 oxonuclear complex [Mn4O 2(CH3COO)7(bipy)2](ClO 4)·3H2O (1) on SiO2 and the successive stacking of SiO2-matrix overlayers around a supported Mn cluster. The structures of supported Mn catalysts were characterized by means of FT-IR spectroscopy, diffuse-reflectance UV/vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and Mn K-edge X-ray absorption fine structure. A ligand exchange reaction between the CH3COO ligand of 1 and surface silanol group produced a SiO2-supported Mn cluster (2), whose coordination structure was similar to 1. Subsequent heating of 2 under vacuum yielded supported Mn clusters (3, 4) through the partial elimination of CH 3COO ligands. The surface-attached Mn clusters of 2, 3, and 4 were easily released to a reaction solution under epoxidation conditions (Mn leaching: approximately 50%), although they were active for epoxidation of trans-stilbene (the conversion of trans-stilbene, 99%, and the selectivity of trans-stilbene epoxid, 96%, for 6 h on 3). We found that the functionalization of the supported Mn cluster on 2 with surface SiO2-matrix overlayers altered the reactivity of the supported Mn cluster. Dimeric Mn species (5c) with reduced Mn oxidation state and coordination numbers was formed together with a reaction nanospace surrounded by the SiO2-matrix overlayers. By optimizing the stacking manner of the SiO2-matrix overlayers, the durability of the Mn catalyst was remarkably improved from leaching (the Mn leaching reached the minimum value of 0.01%), and active and stable epoxidation performances were successfully achieved in the heterogeneous phase (the conversion of trans-stilbene, 97%, and the selectivity of trans-stilbene epoxide, 91%, for 31 h on 5c).
Alternative selective oxidation pathways for aldehyde oxidation and alkene epoxidation on a SiO2-supported Ru-monomer complex catalyst
Tada, Mizuki,Muratsugu, Satoshi,Kinoshita, Mutsuo,Sasaki, Takehiko,Iwasawa, Yasuhiro
experimental part, p. 713 - 724 (2010/04/01)
We have prepared a novel Ru-mononer complex supported on a SiO2 surface by using a Rumonomer complex precursor with a p-cymene ligand, which was found to be highly active for the selective oxidation of aldehydes and the epoxidation of alkenes using O2. The structure of the supported Ru catalyst was characterized by means of FT-IR, solid-state NMR, diffuse-reflectance UV/vis, XPS, Ru K-edge EXAFS, and DFT calculations, which demonstrated the formation of isolatedly located, unsaturated Ru centers behind a p-cymene ligand of the Ru-complex precursor. The site-isolated Ru-monomer complex on SiO2 achieved tremendous TONs (turnover numbers) for the selective oxidation of aldehydes and alkenes; e.g. TONs of 38,800,000 for selective isobutyraldehyde (IBA) oxidation and 2,100,000 for trans-stilbene epoxidation at ambient temperature, which are among the highest TONs in metal-complex catalyzes to our knowledge. We also found that the IBA sole oxidation with an activation energy of 48 kJ mol-1 much more facile than the trans-stilbene epoxidation with an activation energy of 99 kJ mol -1 was completely suppressed by the coexistence of trans-stilbene. The switchover of the selective oxidation pathways from the IBA oxidation to the trans-stilbene epoxidation was explained in terms of energy profiles for the alternative selective oxidation pathways, resulting in the preferential coordination of trans-stilbene to the Ru-complex at the surface. This aspect gives an insight into the origin of the efficient catalysis for selective epoxidation of alkenes with IBA/O2.
Epoxidation of alkenes with H2O2 generated in situ from alcohols and molecular oxygen using N-hydroxyphthalimide and hexafluoroacetone as catalysts
Iwahama, Takahiro,Sakaguchi, Satoshi,Ishii, Yasutaka
, p. 693 - 705 (2007/10/03)
A new epoxidation method of olefins with hydrogen peroxide and/or α- hydroxy hydroperoxide which are generated in situ from an alcohol and molecular oxygen was developed. A variety of alkenes were smoothly epoxidized with molecular oxygen in the presence of an alcohol under the influence of hexafluoroacetone (HFA) and N-hydroxyphthalimide (NHPI) as catalysts. The reaction involves the formation of α-hydroxy hydroperoxide and/or hydrogen peroxide derived from 1-phenylethanol and dioxygen by the action of NHPI and the active oxygen transfer from these hydroperoxides to HFA, giving 2- hydroperoxyhexafluoro-2-propanol which serves as the actual epoxidizing agent.
Epoxidation of alkenes using dioxygen in the presence of an alcohol catalyzed by N-hydroxyphthalimide and hexafluoroacetone without any metal catalyst
Iwahama, Takahiro,Sakaguchi, Satoshi,Ishii, Yasutaka
, p. 727 - 728 (2007/10/03)
A new approach for the epoxidation of alkenes using O2 without any metal catalyst was developed; a variety of alkenes were epoxidized in a regio- and stereoselective manner with O2 in the presence of benzhydrol catalyzed by N-hydroxyphthalimide and hexafluoroacetone.
Manganese (III) acetate dihydrate catalyzed aerobic epoxidation of unfunctionalized olefins in fluorous solvents
Ravikumar,Barbier, Francis,Begue, Jean-Pierre,Bonnet-Delpon, Daniele
, p. 7457 - 7464 (2007/10/03)
Manganese(III) acetate dihydrate is used as a catalyst for the epoxidation of various olefins with molecular oxygen/pivalaldehyde as an oxidant in perfluoro-2-butyltelrahydrofuran. Various types of olefins, including substituted styrenea, stilbenes and cyclic and acyclic alkenes were epoxidized in excellent yields at 25°C. The reaction is stereodependent. Regioselectivity is observed on epoxidation of limonene. Mono- and disubstituted olefins show interesting dichotomy in their reactivity in fluorous solvents such as perfluoro-2-butyltetrahydrofuran and 1,1,1,3,3,3- hexafluoro-2-propanol.
A highly β-stereoselective catalytic epoxidation of Δ5-unsaturated steroids with a novel ruthenium(II) complex under aerobic conditions
Kesavan, Venkitasamy,Chandrasekaran, Srinivasan
, p. 6999 - 7001 (2007/10/03)
Catalytic β-stereoselective epoxidation of Δ5-unsaturated steroid derivatives has been effected by a novel ruthenium(II) bioxazoline complex under aerobic conditions. The reactions are regio- and stereoselective. The reaction conditions provide
