1191-95-3Relevant articles and documents
Formation of a Ruthenium(V) - Imido complex and the reactivity in substrate oxidation in water through the nitrogen non-rebound mechanism
Ishizuka, Tomoya,Kogawa, Taichi,Makino, Misaki,Shiota, Yoshihito,Ohara, Kazuaki,Kotani, Hiroaki,Nozawa, Shunsuke,Adachi, Shin-Ichi,Yamaguchi, Kentaro,Yoshizawa, Kazunari,Kojima, Takahiko
, p. 12815 - 12824 (2019)
A RuII - NH3 complex, 2, was oxidized through a proton-coupled electron transfer (PCET) mechanism with a CeIV complex in water at pH 2.5 to generate a RuV═NH complex, 5. Complex 5 was characterized with various spectroscopies, and the spin state was determined by the Evans method to be S = 1/2. The reactivity of 5 in substrate C-H oxidation was scrutinized in acidic water, using water-soluble organic substrates such as sodium ethylbenzene-sulfonate (EBS), which gave the corresponding 1-phenylethanol derivative as the product. In the substrate oxidation, complex 5 was converted to the corresponding RuIII - NH3 complex, 3. The formation of 1-phenylethanol derivative from EBS and that of 3 indicate that complex 5 as the oxidant does not perform nitrogen-atom transfer, in sharp contrast to other high-valent metal-imido complexes reported so far. Oxidation of cyclobutanol by 5 afforded only cyclobutanone as the product, indicating that the substrate oxidation by 5 proceeds through a hydride-transfer mechanism. In the kinetic analysis on the C-H oxidation, we observed kinetic isotope effects (KIEs) on the C-H oxidation with use of deuterated substrates and remarkably large solvent KIE (sKIE) in D2O. These positive KIEs indicate that the rate-determining step involves not only cleavage of the C-H bond of the substrate but also proton transfer from water molecules to 5. The unique hydride-transfer mechanism in the substrate oxidation by 5 is probably derived from the fact that the RuIV - NH2 complex (4) formed from 5 by 1e-/1H+ reduction is unstable and quickly disproportionates into 3 and 5.
Mechanism of alcohol oxidation mediated by copper(II) and nitroxyl radicals
Ryland, Bradford L.,McCann, Scott D.,Brunold, Thomas C.,Stahl, Shannon S.
, p. 12166 - 12173 (2014)
2,2′-Bipyridine-ligated copper complexes, in combination with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), are highly effective catalysts for aerobic alcohol oxidation. Considerable uncertainty and debate exist over the mechanism of alcohol oxidation mediated by CuII and TEMPO. Here, we report experimental and density functional theory (DFT) computational studies that distinguish among numerous previously proposed mechanistic pathways. Oxidation of various classes of radical-probe substrates shows that long-lived radicals are not formed in the reaction. DFT computational studies support this conclusion. A bimolecular pathway involving hydrogen-atom-transfer from a CuII-alkoxide to a nitroxyl radical is higher in energy than hydrogen transfer from a CuII-alkoxide to a coordinated nitroxyl species. The data presented here reconcile a collection of diverse and seemingly contradictory experimental and computational data reported previously in the literature. The resulting Oppenauer-like reaction pathway further explains experimental trends in the relative reactivity of different classes of alcohols (benzylic versus aliphatic and primary versus secondary), as well as the different reactivity observed between TEMPO and bicyclic nitroxyls, such as ABNO (ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl).
Controlled synthesis of hydroxyapatite-supported palladium complexes as highly efficient heterogeneous catalysts
Mori, Kohsuke,Yamaguchi, Kazuya,Hara, Takayoshi,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
, p. 11572 - 11573 (2002)
Achieving precise control of active species on solid surfaces is one of the most important goals in the development of highly functionalized heterogeneous catalysts. The treatment of hydroxyapatites with PdCl2(PhCN)2 gives two new types of hydroxyapatite-bound Pd complexes. Using the stoichiometric hydroxyapatite, Ca10(PO4)6(OH)2, we found that monomeric PdCl2 species can be grafted on its surface, which are easily transformed into Pd0 particles with narrow size distribution in the presence of alcohols. Such metallic Pd species can effectively promote alcohol oxidation using molecular oxygen and are shown to give a remarkably high TON of up to 236000. Another monomeric PdII phosphate complex can be generated at a Ca-deficient site of the nonstoichiometric hydroxyapatite, Ca9(HPO4)(PO4)5(OH), affording a catalyst with PdII structure and high activity for the Heck and Suzuki reactions. To the best of our knowledge, the PdHAP are one of the most active heterogeneous catalysts for both alcohol oxidation under an atmospheric O2 pressure and the Heck reaction reported to date. These Pd catalysts are recyclable in the above organic reactions. Our approach to catalyst preparation based on the control of Ca/P ratios of hydroxyapatites represents a particularly attractive method for the nanoscale design of catalysts. Copyright
Catalytic reactions of chlorite with a polypyridylruthenium(ii) complex: Disproportionation, chlorine dioxide formation and alcohol oxidation
Hu, Zongmin,Du, Hongxia,Man, Wai-Lun,Leung, Chi-Fai,Liang, Haojun,Lau, Tai-Chu
, p. 1102 - 1104 (2012)
cis-[Ru(2,9-Me2phen)2(OH2) 2]2+ reacts readily with chlorite at room temperature at pH 4.9 and 6.8. The ruthenium(ii) complex can catalyze the disproportionation of chlorite to chlorate and chloride, the oxidation of chlorite to chlorine dioxide, as well as the oxidation of alcohols by chlorite. The Royal Society of Chemistry 2012.
Kinetic study of ruthenium (VI)-catalyzed oxidation of 2-propanol by alkaline hexacyanoferrate (III)
Mucientes,Poblete,Rodriguez,Santiago
, p. 901 - 908 (1999)
The kinetics of Ru(VI)-catalyzed oxidation of 2-propanol by hexacyanoferraie(III) was investigated in alkaline media using a spectrophotometric technique. The reaction shows first order in [Ru(VI)], a Michaelis-Menten-type dependence on [2-propanol], a fractional order in [Fe(CN)63-] and a complicated variation on [OH-]. A reaction mechanism which involves two active catalytic species is proposed. Each of these species forms an intermediate complex with the substrate. These complexes decompose slowly, producing ruthenium(IV) complexes, which are reoxidized by hexacyanoferrate(III) in subsequent steps. The theoretical rate law obtained is in complete agreement with all the experimental observations. Copyright
Transition-Metal-Free Ring-Opening Reaction of 2-Halocyclobutanols through Ring Contraction
?ubiňák, Marek,Edlová, Tereza,Oeser, Petr,Tobrman, Tomá?
, p. 4958 - 4967 (2021)
The present work describes the preparation of halohydrins from 2-halocyclobutanones by means of reactions with Grignard reagents at ?78 °C. We discovered that the prepared cyclobutanols underwent a thermal ring-opening reaction. Depending on the structure of the starting cyclobutanol, different products were formed. More specifically, 1-substituted 2-bromocyclobutan-1-ol was found to open to γ-substituted butyrophenones. A novel 1,3-dihydro-2H-inden-2-ylidene derivative was obtained for indene-derived cyclobutanols. Based on the outcomes of the performed experiments, a mechanism for the ring-opening of cyclobutanols can be proposed.
Mechanistic insight into alcohol oxidation by high-valent iron-oxo complexes of heme and nonheme ligands
Na, Young Oh,Suh, Yumi,Mi, Joo Park,Mi, Sook Seo,Kim, Jinheung,Nam, Wonwoo
, p. 4235 - 4239 (2005)
(Chemical Equation Presented) Iron-mediated oxidation: High-valent iron(IV)-oxo complexes of heme and nonheme ligands are generated in situ and are used in mechanistic studies of alcohol oxidation (see scheme). It is proposed that the oxidation of alcohols occurs by an α-CH hydrogen atom abstraction followed by electron transfer. Porp = porphyrin.
Hydroxyapatite-supported palladium nanoclusters: A highly active heterogeneous catalyst for selective oxidation of alcohols by use of molecular oxygen
Mori, Kohsuke,Hara, Takayoshi,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
, p. 10657 - 10666 (2004)
Treatment of a stoichiometric hydroxyapatite (HAP), Ca10(PO 4)6(OH)2, with PdCl2(PhCN) 2 gives a new type of palladium-grafted hydroxyapatite. Analysis by means of powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX), IR, and Pd K-edge X-ray absorption fine structure (XAFS) proves that a monomeric PdCl2 species is chemisorbed on the HAP surface, which is readily transformed into Pd nanoclusters with a narrow size distribution in the presence of alcohol. Nanoclustered Pd 0 species can effectively promote the alcohol oxidation under an atmospheric O2 pressure, giving a remarkably high turnover number (TON) of up to 236 000 with an excellent turnover frequency (TOF) of approximately 9800 h-1 for a 250-mmol-scale oxidation of 1-phenylethanol under solvent-free conditions. In addition to advantages such as a simple workup procedure and the ability to recycle the catalyst, the present Pd catalyst does not require additives to complete the catalytic cycle. The diameters of the generated Pd nanoclusters can be controlled upon acting on the alcohol substrates used. Oxidation of alcohols is proposed to occur primarily on low-coordination sites within a regular arrangement of the Pd nanocluster by performing calculations on the palladium crystallites.
Generation and Rearrangement of (1-Hydroxycyclopropyl)- A nd (1-Hydroxycyclobutyl)carbene
Deangelo, Joseph D.,Hatano, Sayaka,Thamattoor, Dasan M.
, p. 890 - 893 (2019)
Photolysis of exo-1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclopropan-1-ol and exo-1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclobutan-1-ol in benzene-d6 produces (1-hydroxycyclopropyl)- A nd (1-hydroxycyclobutyl)carbene respectively. It was observed that (1-hydroxycyclopropyl)carbene rearranges to cyclobutanone whereas (1-hydroxycyclobutyl)carbene forms cyclopentanone. Formation of both ketones is attributed to tautomerization of the corresponding enols that arise from ring expansion of the carbenes. Products assignable to intramolecular C-H insertions were not detected in the photolysates.
Reactivity of aqueous Fe(IV) in hydride and hydrogen atom transfer reactions
Pestovsky, Oleg,Bakac, Andreja
, p. 13757 - 13764 (2004)
Oxidation of cyclobutanol by aqueous Fe(IV) generates cyclobutanone in ～70% yield. In addition to this two-electron process, a smaller fraction of the reaction takes place by a one-electron process, believed to yield ring-opened products. A series of aliphatic alcohols, aldehydes, and ethers also react in parallel hydrogen atom and hydride transfer reactions, but acetone and acetonitrile react by hydrogen atom transfer only. Precise rate constants for each pathway for a number of substrates were obtained from a combination of detailed kinetics and product studies and kinetic simulations. Solvent kinetic isotope effect for the self-decay of Fe(IV), kH2O/kD2O, = 2.8, is consistent with hydrogen atom abstraction from water.
