- Visible Light Mediated Reductive Cleavage of C-O Bonds Accessing α-Substituted Aryl Ketones
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C-O σ-bonds in multifaceted benzoin derivatives can be effectively cleaved as acetates using catalytic amounts of [Ru(bpy)3]Cl2 as photoredox catalyst in combination with Hantzsch ester and triethylamine as a sacrificial electron donor. This mild and operationally simple method is applicable to a great variety of substrates. Homo- and cross-benzoins, which are easily accessed by NHC (N-heterocyclic carbene) catalysis, with both electron-withdrawing and electron-donating substituents, including aryl halogenides, can be employed. The deoxygenated counterparts are isolated in good to excellent yields. These broadly accessible, α-substituted (nonsymmetric) aryl ketones are versatilely applicable for further transformations as illustrated by the syntheses of 2-arylbenzofurans.
- Speckmeier, Elisabeth,Padié, Clément,Zeitler, Kirsten
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supporting information
p. 4818 - 4821
(2015/10/12)
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- Palladium-catalyzed oxidation of benzyl ketones to synthesis of α-acetoxy ketones using molecular oxygen
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An efficient procedure for the preparation of α-acetoxy ketone derivatives by palladium-catalyzed oxidation reactions employing molecular oxygen as the sole oxidant has been reported. A variety of benzyl ketones were used to investigate the scope of the r
- Chen, Zheng-Wang,Ye, Dong-Nai,Ye, Min,Liu, Liang-Xian
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supporting information
p. 1388 - 1390
(2013/11/19)
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- Metal-free reductive cleavage of C-O σ-bonds in acyloin derivatives by an organic neutral super-electron-donor
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(Chemical Equation Presented) Neutral organic electron-donor 7, formally a pyridinylidene carbene dimer, effects reductive cleavage of C-O σ-bonds in acyloin derivatives Ar(CO)CRR′OX (X = OAc, OPiv, OBz, OMs) and this represents the first cleavage of C-O σ-bonds by a neutral organic electron-donor. The methodology is applicable to a large array of substrates and the reduced counterparts were isolated in good to excellent yields. For certain substrates, donor 7 behaves as a base, effecting condensation reactions with some acetate ester derivatives of acyloins, leading to butenolides. The variation in reactivity among the different substrates was rationalized. 2009 American Chemical Society.
- Cutulic, Sylvain P. Y.,Findlay, Neil J.,Zhou, Sheng-Ze,Chrystal, Ewan J. T.,Murphy, John A.
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supporting information; experimental part
p. 8713 - 8718
(2009/12/28)
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- Chemoselective control of hydrogenation among aromatic carbonyl and benzyl alcohol derivatives using Pd/C(en) catalyst
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The hydrogenolysis of aromatic ketones and aldehydes quite smoothly give the corresponding methylene compounds via the formation of the intermediary benzyl alcohols in the presence of Pd/C as a catalyst. Therefore, it is extremely difficult to isolate the intermediary benzyl alcohol selectively. This paper describes a mild and chemoselective hydrogenation method of an aromatic carbonyl compound to benzyl alcohol using the 10% Pd/C(en) catalyst and its application to the chemoselective deacetoxylation reaction at the benzylic position in the presence of the benzyl alcohol functionality within the molecule.
- Hattori, Kazuyuki,Sajiki, Hironao,Hirota, Kosaku
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p. 4817 - 4824
(2007/10/03)
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- PHASE-TRANSFER CATALYZED PERMANGANTE OXIDATIONS USING TRISAMINE (TDA-1)
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Oxidation of arylmethanols with KMnO4/TDA-1 under phase-transfer conditions at room temperature gives good to excellent yields of benzaldehydes.A number of other functional groups are also oxidised efficiently with the same reagent system.
- McKillop, Alexander,Mills, Lester S.
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p. 647 - 656
(2007/10/02)
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- Reaction of α,β-Unsaturated Carboxylic Acids with Manganese(III) Acetate in the Presence of Chloride Ion
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The reaction of 3-phenylpropenoic acids with manganese(III) acetate - Cl- complex yielded 1,2,2-trichloro-1-phenylethanes, 1-acetoxy-2,2-dichloro-1-phenylethanes, and 2,2-dichloro-1-phenylethanols. (E)-2,3-Diphenylpropenoic acids gave 2,2-dichloro-1,2-diphenylethanones and 2-acetoxy-1,2-diphenylethanones. 3,3-Diphenylpropenoic acids yielded 2,2-dichloro-1,1-diphenylethenes, 1-acetoxy-2,2-dichloro-1,1-diphenylethanes, 2,2-dichloro-1,1-diphenyl-1-ethanols, and 2-hydroxy-2,2-diphenylethanal.Fluorenylideneacetic acid gave 9-chloro-9-(dichloromethyl)fluorene, 9-acetoxy-9-(dichloromethyl)fluorene, and 9-fluorenone. 1-Cyclohexenecarboxylic acid yielded 1,2-dichlorocyclohexanecarboxylic acid and 1-acetoxy-2-chlorocyclohexanecarboxylic acid.The reaction can be explained in terms of a free-radical mechanism involving manganese(III) acetate - Cl- complexation, addition of Cl. radical, decarboxylation, and the oxidation of chloroethenes which are the reaction intermediates.
- Yonemura, Hiroshi,Nishino, Hiroshi,Kurosawa, Kazu
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p. 3153 - 3160
(2007/10/02)
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- The α-Chlorination of Aryl Ketones with Manganese(III) Acetate in the presence of Chloride Ion
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The reaction of 2-(4-methoxyphenyl)-4-chromanone with Mn(OAc)3 in the presence of LiCl gave 3,3-dichloro-2-(4-methoxyphenyl)-4-chromanone.The reactions of 2-phenyl-4-chromanone, 1-phenyl-1-propanone, 1,2-diphenylethanone, and 1-tetralone similarly yielded α,α-dichloro derivatives in good yields. 2,2,2-Trichloroacetophenones were obtained from 2,2-dichloroacetophenones, but in the absence of LiCl, 2,2-dichloroacetophenones gave 2,2,3,3-tetrachloro-1,4-butanediones.KCl, NaCl, NH4Cl,AlCl3, and CaCl2 were also employed as the Cl- ion source.Synthetic applicability and the reaction mechanisms are discussed briefly.
- Tsuruta, Takehiko,Harada, Tetsuya,Nishino, Hiroshi,Kurosawa, Kazu
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p. 142 - 145
(2007/10/02)
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