- Photocatalytic Carbinol Cation/Anion Umpolung: Direct Addition of Aromatic Aldehydes and Ketones to Carbon Dioxide
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We have developed a new photocatalytic umpolung reaction of carbonyl compounds to generate anionic carbinol synthons. Aromatic aldehydes or ketones reacted with carbon dioxide in the presence of an iridium photocatalyst and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzimidazole (DMBI) as a reductant under visible-light irradiation to furnish the corresponding α-hydroxycarboxylic acids through nucleophilic addition of the resulting carbinol anions to electrophilic carbon dioxide.
- Okumura, Shintaro,Uozumi, Yasuhiro
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supporting information
p. 7194 - 7198
(2021/09/22)
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- Vanadium(I) chloride and lithium vanadium(I) dihydride as selective epimetallating reagents for π- and σ-bonded organic substrates
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Subvalent vanadium(I) salts, of empirical formulas, VCl, vanadium(I) chloride and LiVH2, lithium vanadium(I) dihydride, whose efficient preparation, structural constitution and mode of reaction toward certain organic substrates have been described in a preceding article, are here evaluated in their reactions toward a wide variety of π- and σ-bonded organic substrates, namely carbonyl, imine, azo, alkene, 1,3-diene, nitrile π-bonds and C-X, C-O, C-N and N-N σ-bonds. Compared with the high reactivity of CrCl and LiCrH2 reagents in attacking both types of bonds, the VCl and LiVH2 reagents were much milder and selective in epimetallating π-bonds, often forming the 1:1 adduct of LiVH2 and π-bonded substrate as the major product. Finally, the vanadium reagents showed little tendency to cleave C-O, C-S and C-N bonds and a smaller scope in cleaving C-X bonds than their chromium counterparts. Because of their selectivity these vanadium reagents offer the following preparative promise: 1) smooth McMurry carbonyl coupling to their reductive dimers; 2) deoxygenation of epoxides; 3) selective aromatic C-X reduction; 4) high yields of epimetallated carbonyls or imines as intermediates to α-hydroxy and α-amino acids; 5) 1,4-reductions of 1,3-alkadienes; 6) reductive dimerization of nitriles to ketones; 7) 1,4 or 1,n-epimetallations leading to acyloins or indoles; and 8) reductive dimerizations of azines to produce unusual imidazole derivatives. In explaining the greater kinetic stability of the 1:1 LiVH2 adduct with carbonyl or imine substrates it is pointed out that such epimetallated adducts from LiVH2 would likely be diamagnetic, whereas such adducts from LiCrH2 have an unpaired electron on the Cr center and hence would rupture, so that the electron would be on the C center. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Eisch, John J.,Fregene, Paul O.
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scheme or table
p. 4482 - 4492
(2009/05/07)
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- The epimetallation and carbonation of carbonyl and imino derivatives: Epivanadation route to 2-amino and 2-hydroxy acids
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The feasibility of hydrocarboxylating carbonyl and imino derivatives by the two-step process of epimetallation and carbonation has been demonstrated with the model substrates of 9-fluorenone and 9-fluorenone anil. With lithium vanadium dihydride as the epimetallating agent, such hydrocarboxylation has led to a 75% yield of 9-hydroxy-9-fluorenecarboxylic acid and a 65% yield of 9-(N-phenylamino)-9-fluorenecarboxylic acid, respectively. Some initial success in extending the scope of this reaction to other substrates, such as benzophenone, has been achieved by using other epimetallating agents, like the presumed LiV(CH3)2 and Ti(OPri)2. A brief review of the processes and organic synthetic applications of epimetallation and transfer epimetallation of C-C π-bonds is offered as background.
- Eisch, John J.,Fregene, Paul O.,Gitua, John N.
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p. 4647 - 4653
(2008/03/12)
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- Medicaments for inhalation comprising an anticholinergic and a betamimetic
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A pharmaceutical composition comprising an anticholinergic and a betamimetic of formula 2 optionally together with a pharmaceutically acceptable excipient, the anticholinergic and the betamimetic optionally in the form of their enantiomers, mixtures of their enantiomers, their racemates, their solvates, or their hydrates, processes for preparing them, and their use in the treatment of asthma, COPD, or other inflammatory or obstructive respiratory complaints.
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- Detection and characterization of a transient zwitterion, the 9-carboxylate-9-fluorenyl cation, and its conjugate acid
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Laser flash photolysis of 9-hydroxy-9-fluorenecarboxylic acid in hexafluoro-2-propanol (HFIP) generates a transient with λ(max) at 495 nm that reacts with nucleophiles such as methanol and bromide and is insensitive to oxygen. In the presence of 0.15 M trifluoroacetic acid, a different transient with λ(max) at 560 nm that also reacts with nucleophiles is formed. The 495 and 560 nm species are identified as a zwitterion (the 9-carboxylate-9-fluorenyl cation) and its conjugate acid (the 9-carboxy-9-fluorenyl cation), respectively. The assignment of the zwitterion is supported by the observation of infrared absorptions in the carboxylate region that are quenched by nucleophiles with rate constants similar to those obtained by UV-visible detection. Both the zwitterion and its protonated form are observed at intermediate acid concentrations, leading to an estimate of 1 x 10-2 M-1 for the equilibrium constant for the ionization of the 9-carboxy-9-fluorenyl cation in HFIP. Absolute rate constants for reaction of the zwitterion with alcohols, anionic nucleophiles, and substituted aromatics are reported and compared to data for other 9-fluorenyl cations.
- Lew,Wagner,Angelini, Mark P.,Lee-Ruff,Lusztyk,Johnston
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p. 12066 - 12073
(2007/10/03)
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- Synthetic Routes to Indenopyridine Analogues of Morphactins
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Investigation of a number of synthetic routes to aza analogues of Morphactins led to the synthesis of (RS)-methyl 5H-5-hydroxyindenopyridine-5-carboxylate (6e) and the corresponding carboamide, 6f.
- Braven, J.,Hanson, R. W.,Smith, N. G.
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p. 1051 - 1056
(2007/10/02)
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- Electrocarboxylation de composes carbonyles aliphatiques, aromatiques et vinyliques: interet de l'utilisation d'une anode consommable en magnesium
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In the presence of carbon dioxide in DMF, the electroreduction of carbonyl compounds or α,β-ketoalkenes at high concentration yields respectively α-hydroxyacids and β-ketoacids.The use of a sacrificial magnesium anode allows constant current electrolyses in a diaphragmless cell.
- Mcharek, Slah,Heintz, Monique,Troupel, Michel,Perichon, Jacques
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- Ytterbium Metal-promoted Novel Cross-coupling Reaction between Diaryl Ketones and Electrophiles
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In the presence of Yb metal, diaryl ketones react nucleophilically with octan-2-one, acetonitrile, epoxides, and CO2 to give the corresponding unsymmetrical pinacols, α-hydroxy ketones, 1,3-diols, and α-hydroxy carboxylic acids, respectively.
- Hou, Zhaomin,Takamine, Kan,Aoki, Osamu,Shiraishi, Hiroyuki,Fujiwara, Yuzo,Taniguchi, Hiroshi
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p. 668 - 670
(2007/10/02)
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- Nucleophilic Addition of Lanthanoid Metal Umpoled Diaryl Ketones to Electrophiles
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Ytterbium metal promoted cross-coupling reactions of diaryl ketones with a variety of electrophiles are described.Diaryl ketones treated with 1-2 equiv of Yb metal react smoothly with other ketones, nitriles, epoxides, CO2, etc., to give the corresponding unsymmetrical pinacols, α-hydroxy ketones, 1,3-diols, α-hydroxy carboxylic acids, etc., in good yields respectively.These reactions occur via nucleophilic addition of the intermediates 4a-c to electrophiles.Reaction of benzophenone (1a) with Yb metal is discussed in detail and some information on the composition of the intermediates of the reaction of diaryl ketones with Yb metal are also given.
- Hou, Zhaomin,Takamine, Kan,Aoki, Osamu,Shiraishi, Hiroyuki,Fujiwara, Yuzo,Taniguchi, Hiroshi
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p. 6077 - 6084
(2007/10/02)
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