Aerobic Oxidation of Thiols to Disulfides Catalyzed by Trichlorooxyvanadium.

Kirihara, Masayuki; Okubo, Kumiko; Uchiyama, Tomoyuki; Kato, Yōkō; Ochiai, Yuta; Matsushita, S.; Hatano, Akihiko; Kanamori, Kan

doi:10.1002/chin.200442046

Cited by 2 publications

(3 citation statements)

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“…141 It should be mentioned here that bromination reactions of C-C multiple bonds, aromatic compounds and diketones have been performed with the bromonium ion as obtained by selective oxidation of bromide with H 2 O 2 in the presence of tantalum chloride. 142…”

Section: Activation Of S-containing Compoundsmentioning

confidence: 99%

Interaction of niobium and tantalum pentahalides with O-donors: coordination chemistry and activation reactions

Marchetti

Pampaloni

2012

Chem. Commun.

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The chemistry of niobium and tantalum pentahalides, MX(5), with oxygen compounds is reviewed herein. The polynuclear structure of MX(5) is readily broken by addition of oxygen-containing organic molecules, L, to give either mononuclear or ionic dinuclear coordination adducts. Then activation of the organic ligand may take place favoured by several factors, i.e. low M-X bond energy, high temperature, presence of more than one oxygen function within L, L/M molar ratio ≥ 2. The activation reactions are often uncommon in the context of metal halides; they include the cleavage of C(sp3)-O, C(sp2)-O, C-H and C-C bonds, and eventual successive rearrangements proceeding with C-O or C-C couplings. The recently elucidated reactivity of MX(5) with limited amounts of oxygen compounds will be presented, and possible connections with the relevant MX(5)-directed syntheses reported in the literature will be outlined.

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Section: Activation Of S-containing Compoundsmentioning

confidence: 99%

Interaction of niobium and tantalum pentahalides with O-donors: coordination chemistry and activation reactions

Marchetti

Pampaloni

2012

Chem. Commun.

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“…During the course of our study of the tantalum(V)-catalyzed oxidation of halogen anions to halogen cation equivalents, [6][7][8] we found that 1,3-diphenylpropane-1,3-dione could be quantitatively monobrominated by treatment with TaCl 5 (0.1 equiv), KBr (8.0 equiv), H 2 O 2 (8.0 equiv) and aqueous HCl (8.0 equiv) in chloroform. 6 We further examined the reaction, and found that the monobrominated compound could be obtained in the absence of the tantalum(V) catalyst. The most appropriate conditions are the treatment of 1 with KBr (5.0 equiv), HCl (5.0 equiv), and H 2 O 2 (20.0 equiv) in toluene at room temperature with stirring by a magnetic stirrer (Table 1).…”

mentioning

confidence: 99%

“…6 We further examined the reaction, and found that the monobrominated compound could be obtained in the absence of the tantalum(V) catalyst. The most appropriate conditions are the treatment of 1 with KBr (5.0 equiv), HCl (5.0 equiv), and H 2 O 2 (20.0 equiv) in toluene at room temperature with stirring by a magnetic stirrer (Table 1).…”

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confidence: 99%

Chemoselective Bromination of Active Methylene and Methyne Compounds by Potassium Bromide, Hydrochloric Acid and Hydrogen Peroxide

Kirihara¹,

Ogawa²,

Noguchi³

et al. 2006

Synlett

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Active methylene and methyne compounds can be chemoselectively brominated in high yields using potassium bromide, hydrochloric acid, and hydrogen peroxide at room temperature.Halogenated active methylene and methyne compounds are very important synthetic intermediates for the nucleophilic substitutions in synthetic organic chemistry. The classical methods of halogenation of active methylene and methyne compounds 1 are the reaction with bromine 1 or sulfuryl chloride, 2 however, they suffer from drawbacks such as toxicity of the reagents, generation of acidic gasses after the reaction, or overhalogenation of the aromatic rings in 1. Although a number of new methods of this transformation have previously been developed, most of them have severe disadvantages such as the production of undesirable waste. [3][4][5] Khan and co-workers recently developed chemoselective bromination of active methylene compounds by employing the vanadium pentoxide catalyzed (V 2 O 5 ) oxidation of ammonium bromide (NH 4 Br) by hydrogen peroxide (H 2 O 2 ). 5 The reaction conditions of this method are very mild, and the reaction affords a product in high yield with high chemoselectivity. However, there are still some problems such as the use of a toxic vanadium compound as the catalyst and dichloromethane as the solvent.We now describe the chemoselective bromination of 1 by potassium bromide, hydrochloric acid and 30% hydrogen peroxide in toluene (Scheme 1). This method provides the desired monobromide 2 in high yields, while producing only nontoxic potassium chloride and water as waste.During the course of our study of the tantalum(V)-catalyzed oxidation of halogen anions to halogen cation equivalents, 6-8 we found that 1,3-diphenylpropane-1,3-dione could be quantitatively monobrominated by treatment with TaCl 5 (0.1 equiv), KBr (8.0 equiv), H 2 O 2 (8.0 equiv) and aqueous HCl (8.0 equiv) in chloroform. 6 We further examined the reaction, and found that the monobrominated compound could be obtained in the absence of the tantalum(V) catalyst. The most appropriate conditions are the treatment of 1 with KBr (5.0 equiv), HCl (5.0 equiv), and H 2 O 2 (20.0 equiv) in toluene at room temperature with stirring by a magnetic stirrer (Table 1).Several compounds with general structure 1 were examined under the reaction conditions, and the monobrominated compounds 2 quantitatively obtained in most cases. These results are summarized in Table 2. It is notable that the aromatic ring (entries 1 and 2), the ester group (entries 3-6), the amide group (entries 1 and 2) were inert under the given reaction conditions. Unfortunately, allyl acetoacetate (1k) did not provide the desired compound but complex mixture (entry 8). In this case, the alkene part of 1k also might react with the bromonium ion equivalent. Furthermore, we found that the use of a mechanical stirrer instead of a magnetic stirrer is effective in driving the reaction. In the case of using a mechanical stirrer, 1 quantitatively reacted with KBr (1.0 equiv), HCl (1.0 equiv), and H 2 O 2 (1.2 e...

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Aerobic Oxidation of Thiols to Disulfides Catalyzed by Trichlorooxyvanadium.

Cited by 2 publications

References 1 publication

Interaction of niobium and tantalum pentahalides with O-donors: coordination chemistry and activation reactions

Interaction of niobium and tantalum pentahalides with O-donors: coordination chemistry and activation reactions

Chemoselective Bromination of Active Methylene and Methyne Compounds by Potassium Bromide, Hydrochloric Acid and Hydrogen Peroxide

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