- Facile and Clean Oxidation of Alcohols in Water Using Hypervalent Iodine (III) Reagents
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The facile and efficient oxidation of various alcohols such as benzylic alcohols, primary alcohols, secondary alcohols, and diols in water using the hypervalent iodine(III) reagent, iodosobenzene (PhI=O), with KBr is described. Electrospray ionization (ESI) mass spectrometric studies on the behavior of PhI=O-KBr in aqueous solution suggested that these reactions are induced by the formation of highly reactive iodine species [PhI(Br)nO-]. Further development to recyclable polymer-supported iodine(III) reagent extends the utility of this reaction to afford an environmentally benign method.
- Tohma, Hirofumi,Maegawa, Tomohiro,Takizawa, Shinobu,Kita, Yasuyuki
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- Hypervalent iodine(III)/Et4N+Br- combination in water for green and racemization-free aqueous oxidation of alcohols
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We have found that the use of the PhI(OAc)2/Et4N+Br- combination in water can significantly enhance its oxidation ability and oxidize a wide range of alcohols 1 to carbonyl compounds 2 in good to excellent yields. This clean aqueous oxidation method shows no detectable racemization processes, and even an enolizable ketone 2m could be obtained in an optically pure form from the corresponding chiral alcohol 1m. Utilization of the recyclable reagent 3 as a more practical alternative to PhI(OAc)2 is also successful in these reactions.
- Takenaga, Naoko,Goto, Akihiro,Yoshimura, Misaki,Fujioka, Hiromichi,Dohi, Toshifumi,Kita, Yasuyuki
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- Facile and clean oxidation of alcohols in water using hypervalent iodine(III) reagents
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An environmentally benign oxidation of alcohols in water using iodosobenzene (PhI=O) or a polymer-supported (diacetoxyiodo)benzene (PSDIB) with KBr has been achieved (see scheme). This method results in the catalytic activation of a variety of sluggishly reactive and/or sparsely soluble hypervalent iodine reagents in water under neutral conditions.
- Tohma, Hirofumi,Takizawa, Shinobu,Maegawa, Tomohiro,Kita, Yasuyuki
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- Ytterbium Catalyzed Oxidation of Alcohols to Aldehydes and Ketones by Means of Iodosylbenzene
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Treatment of 1,2-dichloroethane solution of various alcohols with iodosylbenzene in the presence of a catalytic amount of ytterbium(III) nitrate provided the corresponding carbonyl compounds in good to excellent yields.
- Yokoo, Toshiaki,Matsumoto, Kozo,Oshima, Koichiro,Utimoto, Kiitiro
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- Chemo-Selectivity of Group-VIII Metal Catalysts in Hydrogenation of Nonconjugated Enones
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The chemo-selectivity of group-VIII metal catalysts has been examined in the hydrogenation of nonconjugated enones at ambient temperature under an atmospheric pressure of hydrogen.A cobalt catalyst gave high yields of unsaturated alcohols from trialkylated olefinic ketones.Osmium showed the highest selectivity among platinum metal catalysts for the reduction of the carbonyl bond in the hydrogenation of trialkylated olefinic ketones.The hydrogenation of mono- and dialkylated olefinic ketone ordinarily proceeded with a preferential saturation of the olefinic function, regardless of the catalysts.The hydrogenation of 4-methylene- and 4-ethylidenecyclohexanone was accompanied by the formation of diethyl acetals over ruthenium, rhodium, and palladium black catalysts in an ethanol solvent.The acetals were not detected in the hydrogenation of the other enones and over the other catalysts.In addition, the chemoselectivity on the hydrogenation of acyclic enones was examined over nickel and cobalt catalysts treated with small amounts of alkali and carbon monoxide.The amount of unsaturated alcohols increased when the catalyst was treated with alkali in the case of di- and trialkylated olefinic ketones, whereas the characteristics of cobalt, which selectively reduces the ketonic function in trialkylated olefinic ketoones, were completely missing when cobalt was treated with carbon monoxide.
- Ishiyama, Jun-ichi,Maeda, Satoshi,Takahashi, Kazuhiro,Senda, Yasuhisa,Imaizumi, Shin
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p. 1721 - 1726
(2007/10/02)
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