- A Two-Step Oxidative Cleavage of 1,2-Diol Fatty Esters into Acids or Nitriles by a Dehydrogenation–Oxidative Cleavage Sequence
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Dehydrogenative oxidation of vicinal alcohols catalyzed by a commercially 64 wt.% Ni/SiO2 catalyst leads to the formation of α-hydroxyketone. This first step was developed without additional solvent according to two protocols: “under vacuum” or “with an olefin scavenger”. The synthesis of ketols was carried out with good conversions and selectivities. The recyclability of the supported nickel was also studied. Acyloin was then cleaved with oxidative reagent “formic acid/hydrogen peroxide”, which is cheap and can be used on a large scale for industrial oxidation processes. The global yield of this sequential system was up to 80 % to pelargonic acid and azelaic acid monomethyl ester without intermediate purification. By treating the acyloin intermediate with hydroxylamine, nitriles were obtained with a good selectivity.
- Guicheret, Boris,Bertholo, Yann,Blach, Philippe,Raoul, Yann,Métay, Estelle,Lemaire, Marc
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p. 3431 - 3437
(2018/09/06)
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- Oxidation of Vicinal Diols to α-Hydroxy Ketones with H2O2 and a Simple Manganese Catalyst
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α-Hydroxy ketones are valuable synthons in organic chemistry. Here we show that oxidation of vic-diols to α-hydroxy ketones with H2O2 can be achieved with an in situ prepared catalyst based on manganese salts and pyridine-2-carboxylic acid. Furthermore the same catalyst is effective in alkene epoxidation, and it is shown that alkene oxidation with the MnII catalyst and H2O2 followed by Lewis acid ring opening of the epoxide and subsequent oxidation of the alkene to α-hydroxy ketones can be achieved under mild (ambient) conditions.
- Mecozzi, Francesco,Dong, Jia Jia,Saisaha, Pattama,Browne, Wesley R.
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supporting information
p. 6919 - 6925
(2017/12/26)
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- Manganese catalyzed cis-dihydroxylation of electron deficient alkenes with H2O2
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A practical method for the multigram scale selective cis-dihydroxylation of electron deficient alkenes such as diethyl fumarate and N-alkyl and N-aryl-maleimides using H2O2 is described. High turnovers (>1000) can be achieved with this efficient manganese based catalyst system, prepared in situ from a manganese salt, pyridine-2-carboxylic acid, a ketone and a base, under ambient conditions. Under optimized conditions, for diethyl fumarate at least 1000 turnovers could be achieved with only 1.5 equiv. of H2O2 with d/l-diethyl tartrate (cis-diol product) as the sole product. For electron rich alkenes, such as cis-cyclooctene, this catalyst provides for efficient epoxidation.
- Saisaha, Pattama,Pijper, Dirk,Van Summeren, Ruben P.,Hoen, Rob,Smit, Christian,De Boer, Johannes W.,Hage, Ronald,Alsters, Paul L.,Feringa, Ben L.,Browne, Wesley R.
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supporting information; experimental part
p. 4444 - 4450
(2010/11/05)
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- Aqueous biphasic oxidation: A water-soluble polyoxometalate catalyst for selective oxidation of various functional groups with hydrogen peroxide
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A "sandwich" type polyoxometalate, Na12[(WZn 3(H2O)2][(ZnW9O34) 2], was used as an oxidation catalyst in aqueous biphasic reaction media to effect oxidation of alcohols, diols, pyridine derivatives, amines and aniline derivatives with hydrogen peroxide. The catalyst was shown by 183W NMR to be stable in aqueous solutions in the presence of H 2O2 and showed only minimal non-productive decomposition of the oxidant. Secondary alcohols were selectively oxidized to ketones, while primary alcohols tended to be oxidized to the corresponding carboxylic acids, although secondary alcohols were selectively oxidized in the presence of primary alcohols. Vicinal diols yielded carbon-carbon bond cleavage products in very high yields. Pyridine derivatives were oxidized to the respective TV-oxides, but strongly electron-withdrawing moieties inhibited the oxidation reaction. Primary amines were oxidized to the oximes, but significantly hydrolyzed in situ. Aniline derivatives were oxidized to the corresponding azoxy or nitro products depending on the substitution pattern in the aromatic ring. Catalyst recovery and recycle was demonstrated.
- Sloboda-Rozner, Dorit,Witte, Peter,Alsters, Paul L.,Neumann, Ronny
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p. 339 - 345
(2007/10/03)
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- Efficient oxidation of alcohols to carbonyl compounds with molecular oxygen catalyzed by N-hydroxyphthalimide combined with a Co species
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Highly efficient catalytic oxidation of alcohols with molecular oxygen by N-hydroxyphthalimide (NHPI) combined with a Co species was developed. The oxidation of 2-octanol in the presence of catalytic amounts of NHPI and Co(OAc)2 under atmospheric dioxygen in AcOEt at 70 °C gave 2-octanone in 93% yield. The oxidation was significantly enhanced by adding a small amount of benzoic acid to proceed smoothly even at room temperature. Primary alcohols were oxidized by NHPI in the absence of any metal catalyst to form the corresponding carboxylic acids in good yields. In the oxidation of terminal vic-diols such as 1,2-butanediol, carbon-carbon bond cleavage was induced to give one carbon less carboxylic acids such as propionic acid, while internal vic-diols were selectively oxidized to 1,2-diketones.
- Iwahama, Takahiro,Yoshino, Yasushi,Keitoku, Takashi,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 6502 - 6507
(2007/10/03)
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- Dehomologation of Aldehydes via Oxidative Cleavage of Silyl Enol Ethers with Aqueous Hydrogen Peroxide Catalyzed by Cetylpyridinium Peroxotungstophosphate under Two-Phase Conditions
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Dehomologation of aldehydes has been first successfully achieved via oxidative cleavage of silyl enol ethers, derived from aldehydes and trimethylchlorosilane, using aqueous hydrogen peroxide in the presence of a catalytic amount of peroxotungstophophate (PCWP) under phase-transfer conditions. For instance, the oxidation of 1-[(trimethylsilyl)oxy]-1-octene resulting from octanal and Me3SiCl with 35% H2O2 catalyzed by PCWP in dichloromethane at room temperature afforded the one-carbon shorter aldehyde, heptanal, in 79% yield. A variety of silyl enol ethers were also converted into one-carbon shorter aldehydes in good yields. The oxidation under homogeneous conditions using tert-butyl alcohol gave hydrolysis products such as 2-oxooctanol and octanal. It is of interest that [1-(trimethylsilyl)oxy]-1,10-undecadiene involving an enol moiety and a terminal double bond afforded exclusively 9-decenal, in which the enol moiety was selectively oxidized. A plausible reaction path for the oxidative cleavage of silyl enol ethers by the present system has been suggested from the oxidation results of α-[(trimethylsilyl)oxy]styrene.
- Sakaguchi, Satoshi,Yamamoto, Yumiko,Sugimoto, Takuma,Yamamoto, Hiroyo,Ishii, Yasutaka
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p. 5954 - 5957
(2007/10/03)
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- Selective oxidation of vinyl ethers and silyl enol ethers with hydrogen peroxide catalyzed by peroxotungstophosphate
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The oxidation of vinyl and silyl enol ethers with aqueous hydrogen peroxide was first achieved by the use of peroxotungstophosphate (PCWP) as the catalyst. For example, the oxidation of 1-ethoxy-1-octene with a stoichiometric amount of 35% H2O2 in the presence of PCWP (0.5 mol %) in a mixed solvent of methanol and dichloromethane at room temperature gave 1- ethoxy-1-methoxy-2-hydroxyoctane, a synthetic equivalent of 2- hydroxyoctanal, in 70% yield. The oxidation of acyclic silyl enol ethers such as 1-[(trimethylsilyl)oxy]-1-octene under these conditions gave 1-hydroxy-2- octanone in 725 yield, while the same oxidation in dichloromethane alone resulted in cleavage of the enol double bond to form heptanal in 71% yield. Cyclic silyl enol ethers were converted into the corresponding α-hydroxy ketones in 48-71% yields under similar reaction conditions.
- Yamamoto, Hiroyo,Tsuda, Masaya,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 7174 - 7177
(2007/10/03)
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- Direct Catalytic Transformation of Olefins into α-Hydroxy Ketones with Hydrogen Peroxide Catalyzed by Peroxotungstophosphate
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Aliphatic olefins were directly converted into α-hydroxy ketones with acidic aqueous hydrogen peroxide in the presence of catalytic amount of peroxytungstophosphate (PCWP) under the biphasic system using chloroform as a solvent.The acidic medium was necessary to open the resulting epoxide to vic-diol which was subsequently oxidized to α-hydroxy ketones.
- Sakata, Yasuyuki,Katayama, Yuji,Ishii, Yasutaka
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p. 671 - 674
(2007/10/02)
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- AN EFFICIENT CONVERSION OF KETO GROUPS INTO DIHYDROXYACETONE GROUPS: OXIDATION OF ETHYNYLCARBINOL INTERMEDIATES BY USING HYPERVALENT IODINE REAGENT
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A short and efficient synthesis of dihydroxyacetone groups from keto groups involving the oxidation of ethynylcarbinol intermediates with benzene (PIFA), is described.
- Tamura, Yasumitsu,Yakura, Takayuki,Haruta, Jun-ichi,Kita, Yasuyuki
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p. 3837 - 3840
(2007/10/02)
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- Selectivity in the Oxidation of Aliphatic Ketones by Thallic Sulphate in Aqueous Medium
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The effects of temperature, structure and sulphuric acid concentration on the selectivity of the oxidation of aliphatic ketones (R1COR2) (1a-g) by thallic sulphate have been investigated.With increasing temperature the quantity of internal α-hydroxyketone (3a-d) decreases and the quantity of 1-hydroxyketone (2a-d) increases in the oxidation of methyl alkyl ketone (R2>CH3) (1a-d).The same concerns to the oxidation products of hexan-3-one (1e): 2-hydroxy-hexan-3-one (2e) and 4-hydroxy-hexan-3-one (3e), respectively. "The inverse selectivity temperature" (IST) for oxidation of linear methyl alkyl ketones (1a-c) and hexan-3-one (1e) has been found.With the use of the linear free-energy relationship it has been found that the selectivity of the reaction decreases with increasing the polar and steric effects of substituents R1,R2.With increasing the sulphuric acid concentration the selctivity of the oxidation of methyl alkyl ketones (1a, 1d) increases.
- Pechal, Miroslav,Strasak, Milan
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p. 374 - 380
(2007/10/02)
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