16329-23-0Relevant articles and documents
Temperature-dependent immobilization of a tungsten peroxo complex that catalyzes the hydroxymethoxylation of olefins
Chen, Jizhong,Hua, Li,Chen, Chen,Guo, Li,Zhang, Ran,Chen, Angjun,Xiu, Yuhe,Liu, Xuerui,Hou, Zhenshan
, p. 1029 - 1037 (2015/06/08)
Abstract A tungsten peroxo complex stabilized by the bidentate picolinato ligand has been synthesized and then immobilized successfully on imidazole-functionalized silica. The immobilized tungsten-based catalyst was employed as an efficient catalyst for the one-pot synthesis of β-alkoxy alcohols from olefins and methanol with H2O2. Regarding the catalyst evaluation and the results of characterization by the various methods, it was demonstrated that the immobilization of tungsten peroxo complex was highly temperature-dependent. The tungsten peroxo complex can dissociate and diffuse into the liquid phase at reaction temperature, resulting in a homogeneous reaction. Nevertheless, the catalytically active species was anchored on the imidazole-functionalized silica by hydrogen bonding as the temperature was lowered to 0°C after the reaction, which thus offered a highly effective approach for recycling the catalyst for consecutive cycles. In addition, various olefins can be converted to the corresponding β-alkoxy alcohols with good conversion and selectivity under relative mild conditions by H2O2. Running hot and cold: A tungsten peroxo complex (see picture) can dissociate and diffuse into the liquid phase at the reaction temperature, resulting in a homogeneous reaction. After reaction, the catalytically active species was anchored on the functionalized silica by hydrogen-bonding as the temperature was lowered to 0°C. This offers an effective approach for catalyst recovery and recycling.
Synthesis and characterization of norbornanediol isomers and their fluorinated analogues
Grayson, Scott M.,Long, Brian K.,Kusomoto, Shiro,Osborn, Brian P.,Callahan, Ryan P.,Chambers, Charles R.,Willson, C. Grant
, p. 341 - 344 (2007/10/03)
Fluorinated norbornene monomers exhibit the requisite properties for inclusion in 157 nm photoresists, but traditional addition and radical polymerizations with these monomers have failed. Norbornanediols provide an alternate route to these materials via condensation polymerization, and methods have been developed for the efficient synthesis of the exo-2-syn-T- and endo-2-exo-3-dihydroxynorbornanes. Synthesis of the fluorinated analogues is complicated by steric and electronic effects; however, a high-yielding synthesis of endo-2-exo-3-dihydroxynorbornane bearing a 5-endo-[2,2-bis(trifluoromethyl) hydroxyethyl] substituent is reported.
[γ-1,2-H2SiV2W10O40] immobilized on surface-modified SiO2 as a heterogeneous catalyst for liquid-phase oxidation with H2O2
Kasai, Jun,Nakagawa, Yoshinao,Uchida, Sayaka,Yamaguchi, Kazuya,Mizuno, Noritaka
, p. 4176 - 4184 (2007/10/03)
An organic-inorganic hybrid support has been synthesized by covalently anchoring an N-octyldihydroimidazolium cation fragment onto SiO2 (denoted as 1-SiO2). This modified support was characterized by solid-state 13C, 29Si, and 31P NMR spectroscopy, IR spectroscopy, and elemental analysis. The results showed that the structure of the dihydroimidazolium skeleton is preserved on the surface of SiO2. The modified support can act as a good anion exchanger, which allows the catalytically active polyoxometalate anion [γ-1,2-H 2SiV2W10O40]4- (I) to be immobilized onto the support by a stoichiometric anion exchange (denoted as I/1-SiO2). The structure of anion I is preserved after the anion exchange, as confirmed by IR and 51V NMR spectroscopy. The catalytic performance for the oxidation of olefins and sulfides, with hydrogen peroxide (only one equivalent with respect to substrate) as the sole oxidant, was investigated with I/1-SiO2. This supported catalyst shows a high stereospecificity, diastereoselectivity, regioselectivity, and a high efficiency of hydrogen peroxide utilization for the oxidation of various olefins and sulfides without any loss of the intrinsic catalytic nature of the corresponding homogeneous analogue of I (i.e., the tetra-n-butylammonium salt of I, TBA-I), although the rates decreased to about half that with TBA-I. The oxidation can be stopped immediately by removal of the solid catalyst, and vanadium and tungsten species' can hardly be found in the filtrate after removal of the catalyst. These results rule out any contribution to the observed catalysis from vanadium and tungsten species that leach into the reaction solution, which means that the observed catalysis is truly heterogeneous in nature. In addition, the catalyst is reusable for both epoxidation and sulfoxidation without any loss of catalytic performance.
Synthesis of diols using the hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate)
?elik, Murat,Alp, Cemalettin,Co?kun, Betül,Gültekin, M. Serdar,Balci, Metin
, p. 3659 - 3663 (2007/10/03)
1,2- and 1,3-Bis(trifluoroacetoxy) alcohols are easily obtained from the one-pot reaction of alkenes with phenyliodine(III) bis(trifluoroacetate) (PIFA) in the absence of any additive or catalyst. The products were converted into the corresponding diols by ammonolysis. The use of bicyclic alkenes has shown that rearranged 1,3-diacetoxy alcohols are mostly formed as the major products.
Non-heme iron complexes for stereoselective oxidation: Tuning of the selectivity in dihydroxylation using different solvents
Klopstra, Marten,Roelfes, Gerard,Hage, Ronald,Kellogg, Richard M.,Feringa, Ben L.
, p. 846 - 856 (2007/10/03)
A new class of functional models for non-heme iron-based dioxygenases, including [(N3Py-Me)Fe(CH3CN)2](ClO4) 2 and [(N3Py-Bn)Fe(CH3CN)2](ClO 4)2 {N3Py-Me = [di(2-pyridyl)methyl]methyl(2-pyridyl) methylamine; N3Py-Bn = [di(2-pyridyl)methyl]benzyl(2-pyridyl)methylamine}, is presented here. NMR, UV and X-ray analyses revealed that six-coordinate low-spin FeII complexes with the pyridine N-atoms and the tertiary amine functionality of the ligand bound to Fe are formed. The two remaining coordination sites located cis to each other are occupied by labile CH 3CN groups that are easily exchanged by other ligands. We demonstrate that the reactivity and stereoselectivity of the complexes investigated depend on the choice of the solvent. The complexes have been examined as catalysts for the oxidation of both alkanes and olefins in CH3CN. In this solvent alkanes are oxidized to alcohols and ketones and olefins to the corresponding cis-epoxides and cis-diols. In acetone as solvent a different reactivity pattern was found, with, as the most striking example, the trans-dihydroxylation of cis-olefins. 18O-labeling studies in CH3CN establish incorporation of 18O from H218O2 and H218O in both the epoxide and the diol implicating an HO-FeV=18O active intermediate originating from an H 218O-FeIIIOOH species. These results are in full agreement with mechanistic schemes derived for other dioxygenase model systems. Based on labeling studies in acetone an additional oxidation mechanism is proposed for this solvent, in which the solvent acetone is involved. This is the first example of a catalyst that can give cis- or trans-dihydroxylation products, just by changing the solvent. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Methyltrioxorhenium supported on silica tethered with polyethers as catalyst for the epoxidation of alkenes with hydrogen peroxide
Neumann, Ronny,Wang, Tie-Jun
, p. 1915 - 1916 (2007/10/03)
Methyltrioxorhenium has been supported on silica functionalized with polyether tethers; in the absence of an organic solvent, this catalytic assembly catalysed the epoxidation of alkenes with 30% aqueous H2O2 in high selectivity compared to the ring opening products observed in homogeneous media.
Oxygenation of alkenes with t-BuOOH catalysed by β-cyclodextrin borate
Bhat, Shridhar,Chandrasekaran, Srinivasan
, p. 3581 - 3584 (2007/10/03)
β-Cyclodextrin borate catalyses oxygenation of aryl substituted alkenes in the presence of t-BuOOH to afford β-dioxy alcohols in good yields (63-86%).
Catalytic cis to trans Conversions; Dihydroxybicycloheptane and 1,2-Dihydroxyindane
Taylor, Jay E.
, p. 1142 - 1144 (2007/10/02)
cis-2-exo,3-exo-Dihydroxybicycloheptane (2) was isomerized in aqueous solution by an improved procedure to the corresponding trans-glycol 3 in 71percent yield, using Raney nickel at 80 deg C for 56 hours.Similarly, cis-1,2-dihydroxyindane (5) was isomerized by Raney nickel at 60 deg C in 42 hours giving 31percent trans-1,2-dihydroxyindane (7).
