- Reactions of gem-Difluorinated Phosphonium Salts Induced by Light
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gem-Difluorinated phosphonium salts, which are readily obtained from aldehydes and difluoromethylene phosphobetaine, can serve as a source of radicals under reductive conditions. An iridium complex or Hantzsch ester was used as a one-electron reducing agent when irradiated with visible light. The fluorinated radicals were trapped with various alkenes, leading to products either via a photoredox cycle (for the iridium catalyst) or via a hydrogen atom transfer (for the Hantzsch ester).
- Panferova, Liubov I.,Tsymbal, Artem V.,Levin, Vitalij V.,Struchkova, Marina I.,Dilman, Alexander D.
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Read Online
- A FACILE ENTREE TO α-OXO SULFINES BY REACTION OF THIONYL CHLORIDE WITH SILYL ENOL ETHERS
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Silyl enol ethers derived from 1-indanone, 2-indanone, α-tetralone and 4-chromanone react with thionyl chloride to give α-oxo sulfines (3) which can be either isolated or trapped by a cycloaddition reaction with a diene.
- Lenz, Bodo G.,Regeling, Hendrik,Zwanenburg, Binne
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Read Online
- Synthesis of β-nitro ketones from geminal bromonitroalkanes and silyl enol ethers by visible light photoredox catalysis
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Various β-nitro ketones, including those bearing a β-tertiary carbon, were prepared from geminal bromonitroalkanes and trimethylsilyl enol ethers of a broad range of ketones by visible light photoredox catalysis, which were then easily converted into β-amino ketones, 1,3-amino alcohols, α,β-unsaturated ketones, β-cyano ketones and γ-nitro ketones.
- Cao, Haoying,Ma, Shanshan,Feng, Yanhong,Guo, Yawen,Jiao, Peng
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supporting information
p. 1780 - 1783
(2022/02/17)
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- Three-Component Coupling of Acyl Fluorides, Silyl Enol Ethers, and Alkynes by P(III)/P(V) Catalysis
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We report herein on the phosphine-catalyzed hydrovinylation reaction by three-component coupling of acyl fluorides, silyl enol ethers, and alkynoates. The key to the success of the reaction is the formal transmetalation between pentacoordinate P(V) species (i.e., fluorophosphorane) and a silyl enol ether, which allows for C-C bond formation between the polarity-mismatched sites. The bond formation that cannot be attained even by transition metal catalysis is accomplished by a P(III)/P(V) manifold.
- Fujimoto, Hayato,Kusano, Momoka,Kodama, Takuya,Tobisu, Mamoru
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supporting information
p. 18394 - 18399
(2021/11/22)
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- Photoinduced Deaminative Alkylation for the Synthesis of γ-Ketoesters via Electron Donor–Acceptor Complex Formation
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Visible-light-induced deaminative alkylation of Katritzky salts with silyl enol ethers has been developed. The reaction can proceed efficiently through electron donor–acceptor complex formation, avoiding the use of precious metal complexes or synthetically elaborate organic dyes. A series of functionalized γ-ketoesters was successfully obtained with good functional group tolerance and compatibility under mild and straightforward conditions.
- Wang, Jia-Xin,Ge, Wei,Xing, Wei-Long,Fu, Ming-Chen
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supporting information
p. 18224 - 18231
(2021/12/13)
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- The Cyclopropane Ring as a Reporter of Radical Leaving-Group Reactivity for Ni-Catalyzed C(sp3)-O Arylation
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The ability to understand and predict reactivity is essential for the development of new reactions. In the context of Ni-catalyzed C(sp3)-O functionalization, we have developed a unique strategy employing activated cyclopropanols to aid the design and optimization of a redox-active leaving group for C(sp3)-O arylation. In this chemistry, the cyclopropane ring acts as a reporter of leaving-group reactivity, since the ring-opened product is obtained under polar (2e) conditions, and the ring-closed product is obtained under radical (1e) conditions. Mechanistic studies demonstrate that the optimal leaving group is redox-active and are consistent with a Ni(I)/Ni(III) catalytic cycle. The optimized reaction conditions are also used to synthesize a number of arylcyclopropanes, which are valuable pharmaceutical motifs.
- Mills, L. Reginald,Monteith, John J.,Dos Passos Gomes, Gabriel,Aspuru-Guzik, Alán,Rousseaux, Sophie A. L.
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supporting information
p. 13246 - 13254
(2020/09/01)
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- Conversion of Carbonyl Compounds to Olefins via Enolate Intermediate
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A general and efficient protocol to synthesize substituted olefins from carbonyl compounds via nickel catalyzed C—O activation of enolates was developed. Besides ketones, aldehydes were also suitable substrates for the presented catalytic system to produce di- or tri- substituted olefins. It is worth noting that this approach exhibited good tolerance to highly reactive tertiary alcohols, which could not survive in other reported routes for converting carbonyl compounds to olefins. This method also showed good regio- and stereo-selectivity for olefin products. Preliminary mechanistic studies indicated that the reaction was accomplished through nickel catalyzed C—O activation of enolates, thus offering helpful contribution to current enol chemistry.
- Cao, Zhi-Chao,Xu, Pei-Lin,Luo, Qin-Yu,Li, Xiao-Lei,Yu, Da-Gang,Fang, Huayi,Shi, Zhang-Jie
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p. 781 - 785
(2019/06/24)
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- C?O coupling of Malonyl Peroxides with Enol Ethers via [5+2] Cycloaddition: Non-Rubottom Oxidation
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Malonyl peroxides act both as oxidants and reagents for C?O coupling in reactions with methyl and silyl enol ethers. In the proposed conditions, the oxidative C?O coupling of malonyl peroxides with enol ethers selectively proceeds, bypassing the traditional Rubottom hydroxylation of enol ethers by peroxides. It was observed that the oxidative [5+2] cycloaddition of malonyl peroxides and enol ethers is the key stage of the discovered process. Oxidative C?O coupling of silyl enol ethers leads to the formation of α-acyloxyketones with a free carboxylic acid group. A specially developed preparative one-pot procedure transforms ketones via silyl enol ethers formation and the following coupling into α-acyloxyketones with yields 35–88%. The acid-catalyzed coupling with methyl enol ethers gives remarkable products while retaining the easily oxidizable enol fragment. Furthermore, these molecules contain a free carboxylic acid group, thus these nontrivial products contain two usually incompatible acid and enol ether groups. (Figure presented.).
- Vil', Vera A.,Gorlov, Evgenii S.,Bityukov, Oleg V.,Barsegyan, Yana A.,Romanova, Yulia E.,Merkulova, Valentina M.,Terent'ev, Alexander O.
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supporting information
p. 3173 - 3181
(2019/05/15)
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- An Electrophilic Trifluoromethylthiolation of Silylenol Ethers and β-Naphthols with Diethylaminosulfur Trifluoride and (Trifluoromethyl)trimethylsilane
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An efficient and general trifluoromethylthiolation of silylenol ethers and β-naphthols have been accomplished employing the combination of diethylaminosulfur trifluoride (DAST) and (trifluoromethyl)trimethylsilane (CF3TMS) as source of electrophilic trifluoromethylthio moiety for the synthesis of α-trifluoromethylthiolated carbonyl compounds and β-naphthols in good yields. Important features of this method include wide functional group tolerance and use of readily available DAST/CF3TMS. Potential of the methodology was demonstrated via the synthesis of α-trifluoromethylthiolated (+)-4-cholesten-3-one and naphthoquinone. (Figure presented.).
- Saravanan, Perumal,Anbarasan, Pazhamalai
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supporting information
p. 2894 - 2899
(2018/08/17)
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- Synthesis of 3-Fluoropyridines via Photoredox-Mediated Coupling of α,α-Difluoro-β-iodoketones with Silyl Enol Ethers
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A method for the synthesis of diversely substituted 3-fluoropyridines from two ketone components is described. The reaction involves photoredox coupling of α,α-difluoro-β-iodoketones with silyl enol ethers catalyzed by fac-Ir(ppy)3 under blue LED irradiation with subsequent one-pot condensation with ammonium acetate. Based on cyclic voltammetry studies, it was determined that α,α-difluoro-β-iodoketones are reduced notably easier compared to 2,2,2-trifluoro-1-iodoethane, which may be ascribed to the influence of the carbonyl group.
- Scherbinina, Sofya I.,Fedorov, Oleg V.,Levin, Vitalij V.,Kokorekin, Vladimir A.,Struchkova, Marina I.,Dilman, Alexander D.
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p. 12967 - 12974
(2017/12/15)
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- Difluorohomologation of ketones
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A method for the homologation of ketones with the CF2 fragment is described. The reaction involves silylation, room-temperature difluorocyclopropanation of silyl enol ethers, and selective ring opening of cyclopropanes under acidic conditions. The whole three-step sequence is conveniently performed in a one-pot mode.
- Kosobokov, Mikhail D.,Levin, Vitalij V.,Struchkova, Marina I.,Dilman, Alexander D.
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supporting information
p. 760 - 763
(2015/03/05)
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- Iron- or silver-catalyzed oxidative fluorination of cyclopropanols for the synthesis of β-fluoroketones
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The FeIII- or AgI-catalyzed oxidative fluorination of cyclopropanols via radical rearrangement is disclosed. This process features a straightforward and highly effective protocol for the site-specific synthesis of β-fluoroketones and represents an expedient method for the synthesis of γ-, δ- and ε-fluoroketones. Notably, this reaction proceeds at room temperature and tolerates a diverse array of cyclopropanols.
- Ren, Shichao,Feng, Chao,Loh, Teck-Peng
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supporting information
p. 5105 - 5109
(2015/05/13)
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- Halogenative difluorohomologation of ketones
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A method for the difluorohomologation of ketones accompanied by halogenation of a C-H bond is described. The reaction involves silylation, difluorocarbene addition using Me3SiCF2Br activated by a bromide ion, and halogenation of intermediate cyclopropanes with N-bromo- or N-iodosuccinimide. The whole process is performed without isolation of intermediates. The resulting α,α-difluoro-β-halo-substituted ketones can be readily converted into fluorine containing pyrazole derivatives and oxetanes.
- Fedorov, Oleg V.,Kosobokov, Mikhail D.,Levin, Vitalij V.,Struchkova, Marina I.,Dilman, Alexander D.
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p. 5870 - 5876
(2015/06/16)
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- Trapping of azidocarbenium ion: A unique route for azide synthesis
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For the first time, a sensitive azidocarbenium ion intermediate has been trapped with various nucleophiles to provide azides in excellent chemoselectivity. This provides a novel approach for the chemoselective synthesis of primary and secondary benzyl azides from aldehydes in a one-pot reaction. Enantioselective nucleophilic addition to the azidocarbenium ion has also been initiated.
- Pramanik, Suman,Ghorai, Prasanta
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supporting information
p. 2104 - 2107
(2014/05/06)
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- METHOD FOR PRODUCING SILYLENOL ETHERS
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The present invention provides a method for producing a silyl enol ether compound, which is convenient, has highly broad utility and places a low environmental load (less waste). The present invention relates to a method for producing silyl enol ether compound (3), including reacting ketone or aldehyde compound (1) with allylsilane compound (2) in the presence of a base and 0.00001 to 0.5 equivalents of an acid catalyst relative to ketone or aldehyde compound (1), wherein R1 is a hydrogen atom, an alkyl group, an aryl group or the like; R2 and R3 are each a hydrogen atom, a halogen atom, an alkyl group, an aryl group or the like; R1 and R3, R1 and R2, or R2 and R3 optionally form a ring, together with the carbon atom(s) bonded thereto; R4 , R5 and R6 are each a hydrogen atom, an alkyl group or the like; two of R4, R5 and R6 optionally form a ring; R7, R8, R9, R10 and R11 are each a hydrogen atom, an alkyl group or the like; two of R7, R8, R9, R10 and R11 optionally form a ring.
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Paragraph 0102
(2013/03/26)
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- A novel process for synthesis of atovaquone
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A stereospecific efficient process for synthesis of atovaquone i.e. trans-2-[4-(4-chlorophenyl)cyclohexyl ]-3-hydroxy-1,4-naphthalenedione and its cis isomer from commercially available raw materials such as α-tetralone and 4-(4-chlorophenyl)cyclohexanone
- Roy, Bhairab N,Singh, Girij P,Lathi, Piyush S,Agrawal, Manoj K,Mitra, Rangan,Trivedi, Anurag
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p. 1299 - 1312
(2014/01/06)
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- NOVEL METHOD FOR PREPARATION OF ATOVAQUONE
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Provided is a process of preparation of 2-[trans,-4-(4'-chlorophenyl)cyclohexyl]-3-hydroxy- 1,4-naphthoquinone, i.e. Atovaquone [I] which is cost effective, green, and eco-friendly process, without separation of any diastereomers or geometric isomers of intermediates obtained during the reactions. Also provided is separation of 'cis' and 'trans ' isomer of intermediates VI, VII and VIII through selective crystallization in an appropriate solvent. A method for converting 2-[cis,-4-(4'-chlorophenyl)cyclohexyl]-3-hydroxy-1,4-naphthoquinone to 2-[trans-4-(4'-chlorophenyl)cyclohexyl]-3-hydroxy-l,4-naphthoquinone in presence of Lewis/ Bronsted acid is also provided. A process for preparation of compound 2-(4-(4- chlorophenyl)- 1 -hydroxy cyclohexyl)-3,4-dihydronaphthalen- 1 (2H)-one [IV] comprising condensation of (1,2-dihydronaphthalen-4-yloxy)trimethylsilane [II] with 4-(4- chlorophenyl)cyclohexanone [III] in presence of Lewis acid in organic solvent. The invention also encompasses a highly efficient and atomeconomic process for synthesis of compound [III] i.e. 4-(4-chlorophenyl)cyclohexanone as well as a process for synthesis of 2-[cis-4-(4'- chlorophenyl)cyclohexyl]-3-hydroxy-l,4-naphthoquinone. Further provided is a process for isomerization of cis- Atovaquone i.e. 2-[cis-4-(4'-chlorophenyl)cyclohexyl]-3-hydroxy-l,4- naphthoquinone to tnms-Atovaquone i.e. 2-[trans-4-(4'-chlorophenyl)cyclohexyl]-3- hydroxy- 1,4-naphthoquinone in presence of Lewis acid.
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Page/Page column 21-22
(2012/12/13)
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- Synthesis of novel mast cell-stabilising and anti-allergic 1,2,3,4-tetrahydro-1-naphthalenols and related compounds
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In a continuation of our studies into indan and tetralin systems as novel modulators of allergic and inflammatory phenomena, we have extended our work to include dimers linked via C-C bonds. Of these compounds, 2-Benzyl-2-[2-phenyl-1- ethenyl]-1,2,3,4-tet
- Barlow, James W.,McHugh, Aengus P.,Woods, Orla,Walsh, John J.
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experimental part
p. 1545 - 1554
(2011/05/06)
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- Metal nitrite: A powerful oxidizing reagent
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An efficient and simple source of nitroso reagents and their oxidation reactions are described. The combination of a Lewis acid and a metal nitrite was applied to the oxidation of silyl enol ethers. Amino acid and peptide derivatives were easily accessed through in situ C-C bond cleavage of fully substituted silyl enol ethers upon oxidation.
- Baidya, Mahiuddin,Yamamoto, Hisashi
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supporting information; body text
p. 13880 - 13882
(2011/10/09)
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- N-heterocyclic carbene-catalyzed silyl enol ether formation
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N-Heterocyclic carbenes (NHCs) were found to catalyze the silyl transfer from trialkylsilyl ketene acetals to ketones. In the presence of a catalytic amount of NHC 3 (IAd, 0.1 to 5 mol%), a series of enolizable ketones as well as cyclohexanecarboxaldehyde
- Song, Jinhua J.,Tan, Zhulin,Reeves, Jonathan T.,Fandrick, Daniel R.,Yee, Nathan K.,Senanayake, Chris H.
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supporting information; experimental part
p. 877 - 880
(2009/04/07)
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- In situ generation of Mes2Mg as a non-nucleophilic carbon-centred base reagent for the efficient one-pot conversion of ketones to silyl enol ethers
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Treatment of commercially available MesMgBr with 1,4-dioxane produces the key Mes2Mg reagent in situ which then mediates the deprotonation of ketones to deliver trimethylsilyl enol ethers, at readily accessible temperatures and without any nucleophilic addition, in an expedient and high yielding one-pot process. The Royal Society of Chemistry.
- Kerr, William J.,Watson, Allan J. B.,Hayes, Douglas
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experimental part
p. 1238 - 1243
(2008/10/09)
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- Di-tert-butylmagnesium as an atom-efficient, carbon-centred base reagent for the preparation of silyl enol ethers from ketones
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Di-tert-butylmagnesium has been found to be a reactive, yet non-nucleophilic and non-reductive, carbon-centred base for the deprotonation of a series of ketones. This reagent demonstrates equally high reactivity when used as either the pre-formed reagent, or in a more accessible one-pot protocol from the parent Grignard reagent, and offers improved atom-efficiency over more traditionally employed bases. Georg Thieme Verlag Stuttgart.
- Kerr, William J.,Watson, Allan J. B.,Hayes, Douglas
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experimental part
p. 1386 - 1390
(2009/04/06)
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- Bismesitylmagnesium: A thermally stable and non-nucleophilic carbon-centred base reagent for the efficient preparation of silyl enol ethers
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Bismesitylmagnesium has been established as an accessible, practical, convenient, and non-nucleophilic carbon-centred base reagent for efficient access to silyl enol ethers from a series of ketone substrates at readily utilisable temperatures. The Royal Society of Chemistry.
- Kerr, William J.,Watson, Allan J. B.,Hayes, Douglas
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p. 5049 - 5051
(2008/09/17)
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- Chiral and achiral lithium amides having a fluorous ponytail: Preparation and evaluation as a recycling reagent for lithium enolate generation
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Diisopropylamine derivatives bearing a perfluoroalkyl chain were prepared and converted to the corresponding lithium amides by treatment with n-butyllithium. The fluorous lithium amides reacted with ketones to efficiently produce lithium enolates. Asymmetric deprotonation of prochiral ketones was also studied using lithium amides derived from chiral fluorous amines, which gave optical yields comparable with the parent nonfluorous chiral lithium amides. These reusable fluorous amines can be easily recovered by liquid-liquid extraction or chromatographic separation. Georg Thieme Verlag Stuttgart.
- Matsubara, Hiroshi,Maeda, Louis,Sugiyama, Hiroyuki,Ryu, Ilhyong
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p. 2901 - 2912
(2008/03/13)
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- Investigations into the C-deuteriation of aryl alkyl ketones using urea as a pro-base in the presence of a deuterium donor
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Results are reported on the regioselective C-deuteriation of a series of enolates derived from the deprotonation of aryl alkyl ketones using dilithiated urea as the pro-base in the presence of a suitable deuterium donor. Copyright
- Coumbarides, Gregory S.,Eames, Jason,Suggate, Michael J.,Weerasooriya, Neluka
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p. 641 - 652
(2007/10/03)
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- Investigations into the C-deuteriation of silyl enol ethers derived from aryl alkyl ketones
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Results are reported on the regioselective C-deuteriation of a series of silyl enol ethers derived from aryl alkyl ketones using deuterium (D 2) gas as the deuterium source and palladium-on-barium sulfate as the mediator. These results highlight the numerous reaction pathways and different product types available from simple deuteriation of substituted enol precursors. Copyright
- Buksha, Svitlana,Coumbarides, Gregory S.,Dingjan, Marco,Eames, Jason,Suggate, Michael J.,Weerasooriya, Neluka
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p. 757 - 771
(2007/10/03)
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- Catalytic synthesis of α-hydroxy ketones using organic-inorganic hybrid polymer
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Oxidation of silyl enolates was found to be smoothly catalyzed by [Cu(bpy)(BF4)2(H2O)2(bpy)] n (bpy = 4,4′-bipyridine) under molecular oxygen, and provided the corresponding α-hydroxy carbonyl compounds in high yield. The insoluble organic-inorganic hybrid polymer was readily recovered by centrifugation after the completion of reaction, and the recovered catalyst could be reused. Copyright
- Arai, Takayoshi,Takasugi, Hitomi,Sato, Toru,Noguchi, Hiroshi,Kanoh, Hirofumi,Kaneko, Katsumi,Yanagisawa, Akira
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p. 1590 - 1591
(2007/10/03)
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- Investigations on the efficiency of regioselective C-deuteration of Endocyclic enolates
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Regioselective C-deuteration of a series of Endocyclic enolates (derived from cyclic aryl ketones) was efficiently achieved by quenching the corresponding "base-free" enolate in the presence of a suitable deuterium source. We discuss the structural nature of the deuterium donor and comment on the use of additives within this deuteration step.
- Eames, Jason,Weerasooriya, Neluka,Coumbarides, Gregory S.
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p. 181 - 187
(2007/10/03)
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- Investigations into the regioselective deuteriation of enolates derived from silyl enol ethers and enolacetates
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Results are reported on the regioselective C-deuteriation of a series of enolates derived from the addition of MeLi to the related enolacetate and silyl enol ether and discussed in terms of the similarity between these methods; comments are made on the possible role of the additive, lithium tertbutoxide. Copyright
- Coumbarides, Gregory S.,Eames, Jason,Weerasooriya, Neluka
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p. 871 - 879
(2007/10/03)
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- Transition metal-catalyzed oxidations. 12 : α-Chlorination of silylenol ethers with tert-butyl hydroperoxide and TiCl2(OiPr)2
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Enolsilyl ethers (4, 6, 8, 10, 12, 14) are chlorinated to the α-monochloro ketones (5, 7, 9, 11, 13, 15) with tert-butyl hydroperoxide in the presence of dichlorotitanium diisopropoxide in 69 - 92% yield. WILEY-VCH Verlag GmbH, 1999.
- Krohn, Karsten,Steingroever, Klaus,Vinke, Ingeborg
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- An efficient α-hydroxylation of carbonyls using the HOF·CH3CN complex
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The complex HOF·CH3CN, made directly from fluorine and aqueous acetonitrile, was used for α-hydroxylation of various ketones, esters and acids via their trimethyl silyl enol ethers. The reaction is usually complete in a few minutes at room temperature or below and has high yields.
- Dayan, Sharon,Bareket, Yifat,Rozen, Shlomo
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p. 3657 - 3664
(2007/10/03)
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- Catalytic enantioselective amination of enolsilanes using C2-symmetric copper(II) complexes as chiral lewis acids
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(Matrix presented) [Cu(S,S)-t-Bu-box](OTf)2 (1) catalyzes the enantioselective amination of enolsilanes with azodicarboxylate derivatives. Isomerically pure enolsilanes of aryl ketones, acylpyrroles, and thioesters added to the azo-imide in gre
- Evans, David A.,Johnson, Douglas S.
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p. 595 - 598
(2008/02/11)
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- Allylindation of 6-substituted 2-hydroxy-l-tetralones in aqueous and organic media. stereochemistry and competition studies
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A systematic investigation of the stereoselectivity associated with coupling reactions involving the allylindium reagent and 6-substituted 2-hydroxy-l-tetralones is presented. In each instance, the allylations were carried out in water, 50% aqueous THF, a
- Lobben, Paul C.,Paquette, Leo A.
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p. 6990 - 6998
(2007/10/03)
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- Easy preparation of enoxysilanes from aldehydes and ketones catalyzed by samarium diiodide
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Ketones and α-substituted aldehydes are converted to trimethylsilyl enol ethers by reaction with the trimethylsilyl ketene acetal of methyl isobutyrate in dichloromethane in presence of a catalytic amount of samarium diiodide.
- Hydrio, Jerome,Van De Weghe, Pierre,Collin, Jacqueline
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- α-nitration of ketones via enol silyl ethers. Radical cations as reactive intermediates in thermal and photochemical processes
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Highly colored (red) solutions of various enol silyl ethers and tetranitromethane (TNM) are readily bleached to afford good yields of α-nitro ketones in the dark at room temperature or below. Spectral analysis show the red colors to be associated with the intermolecular 1:1 electron donor-acceptor (EDA) complexes between the enol silyl ether and TNM. The formation of similar vividly colored EDA complexes with other electron acceptors (such as chloranil, tetracyanobenzene, tetracyanoquinodimethane, etc.) readily establish enol silyl ethers to be excellent electron donors. The deliberate irradiation of the diagnostic (red) charge-transfer absorption bands of the EDA complexes of enol silyl ethers and TNM at -40 °C affords directly the same α-nitro ketones, under conditions in which the thermal reaction is too slow to compete. A common pathway is discussed in which the electron transfer from the enol silyl ether (ESE) to TNM results in the radical ion triad [ESE?+, NO2?, C(NO2)3-]. A subsequent fast homolytic coupling of the cation radical of the enol silyl ether with NO2? leads to the α-nitro ketones. The use of time-resolved spectroscopy and the disparate behavior of theisomeric enol silyl ethers of α- and β-tetralones as well as of 2-methylcyclohexanone strongly support cation radicals (ESE?+) as the critical intermediate in thermal and photoinduced electron-transfer as described in Schemes 1 and 2, respectively.
- Rathore, Rajendra,Kochi, Jay K.
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p. 627 - 639
(2007/10/03)
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- Two-Step Synthesis of (γ,γ-Difluoroallyl)carbonyl Compounds via Addition of 1,1,2-Trichloro-2,2-difluoroethyl Radical to Silyl Enol Ethers Followed by Reductive Dechlorination
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Ru(II)- or Cu(I)-induced radical reaction of CF2ClCCl2. radical (2), regioselectively derived from CF2ClCCl3, to trimethylsilyl enol ethers and a ketene silyl acetal yields (β,β,γ-trichloro-γ,γ-difluoropropyl)carbonyl compounds 5 as the intermediates.Spontaneous dehydrochlorination affords carbonyl compounds 4.Reductive dechlorination of 4 with zinc gave γ,γ-difluoroallyl ketones 7a-e and an ester 7f.In some cases, Ni(0)-catalyzed reduction with zinc is superior than the simple hydrodechlorination.
- Okano, Takashi,Shimizu, Toshihiro,Sumida, Koji,Eguchi, Shoji
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p. 5163 - 5166
(2007/10/02)
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- Synthesis of γγγ-trifluorocarbonyl compounds
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γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF3-CH2-) on the α-methylene group of a ketone.
- Laurent,Lesniak
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p. 8091 - 8092
(2007/10/02)
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- Synthesis and 13C FT NMR spectroscopy of furan-2,3-dione derivatives
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Substituted furan-2,3-diones were obtained by condensation of oxalyl chloride with silyl enol ether of para-substituted acetophenones (R = H, CH3, OCH3, Cl, Br, F), propiophenone, 1-tetralone, 6-methoxytetralone and 1-benzosuberone.The spectroscopic data obtained from IR, UV, 1H and 13C NMR studies are quite similar whichever are the substituents. furan-2,3-dione / 1H and 13C NMR / UV and IR spectra
- Hnach, M.,Aycard, J. P.,Zineddine, H.
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p. 393 - 396
(2007/10/02)
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- An analogue of the antioestrogen tamoxifen of sufficient rigidity to exist as distinct enantiomers: Synthesis and conformtional dynamics studies
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The conformationally constrained tamoxifen analogue 1-methyl-8-phenyl-9-[4-[2-(dimethylamino)ethoxy]phenyl]-6,7 dihydro-5H-benzocycloheptene has been synthesised. A key synthetic step is a novel method for introduction of a methyl group into the aromatic ring of benzosuberone by enolate oxygen directed lithiation. Conformational studies were carried out on the methoxy precursor of the above compound. Dynamic 1H NMR revealed a free energy barrier to racemisation of enantiomeric atropisomers, ΔG[ = 20 (±1) kcal mol-1. It could be separated by chromatography at -5°C on (+)-poly(triphenylmethylmethacryate) into enantiomers which racemised with t( 1/2 ) 1.8 h at -5.2°C corresponding to Δ[ = 20.9 kcal mol-1. The difficulties in designing analogues having a greater degree of conformational constraint are discussed.
- McCague
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- Synthesis and Reactivity of Benzylic Epoxides Derived from 1,2,3,9,10,10a-Hexahydrophenanthrene. Search for a Unified Mechanism for the Ring Opening of 2-Aryloxiranes
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The diastereoisomeric benzylic epoxides 4a and 4b were synthesized, and their ring-opening reactions under acidic conditions were compared with those of the known epoxides 2 and 3.The chemical behavior of 4 more nearly resembles that of 3, thus suggesting that the differences in chemical behavior between 2 and 3 could be ascribed to the different conformational rigidity of the aryl in these systems.The ring opening of 4 forms significant amounts of unsaturated alcohol and ketone in addition to the diastereoisomeric diols.The results obtained in the present study are difficult to explain by means of either of the two mechanistic schemes suggested for 2-aryloxiranes.
- Chini, Marco,Crotti, Paolo,Macchia, Franco
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p. 3930 - 3936
(2007/10/02)
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- A NEW PRACTICAL SYNTHESIS OF SILYL ENOL ETHERS. PART.I. FROM SIMPLE ALDEHYDES AND KETONES.
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A new, practical route to enoxysilanes is described from simple enolizable aldehydes or ketones, using the trimethylchlorosilane-sodium iodide-tertiary amine reagent in acetonitrile.From certain aldehydes, an onium intermediate has been isolated.A conformational study of this onium intermediate and a thermal unimolecular syn-elimination process may explain the stereoselectivity of the reaction.Such an interpretation can be extended to all the aldehydes and ketones considered.Steric factors related to the nature both of the cabonyl derivative and of the amine play a capital role for the regio- as well as for the stereo-control of the reaction.
- Cazeau, P.,Duboudin, F.,Moulines, F.,Babot, O.,Dunogues, J.
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p. 2075 - 2088
(2007/10/02)
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- The Chemistry of Aryllead(IV) Tricarboxylates. Reaction with Silyl Enol Ethers
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The trimethylsilyl enol ether of acetophenone (1) and p-methoxyphenyllead triacetate (2) react to give (p-methoxyphenyl)phenacyllead(IV) diacetate (4) in high yield.This plumbation reaction has been studied for a number of ketone trimethylsilyl enol ethers and aryllead triacetates, and it would appear that it is probably limited to aryl ketone trimethylsilyl enol ethers.The trifluoroacetic acid catalysed break down of these α-plumbated ketones to substituted deoxybenzoins has been examined in considerable detail.The thermal decomposition of one of the lead compounds to a deoxybenzoin derivative has also been examined.
- Bell, Craig H.,Pinhey, John T.,Sternhell, Sever
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p. 2237 - 2245
(2007/10/02)
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- Reactions of Trialkylsilyl Trifluoromethanesulfonates, I. - Synthesis of Trialkylsilyl Enol Ethers
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The reactions of the ketones 2,2-bromoketones 6, α,β-unsaturated ketones 8, 1,2-diketones, and aliphatic aldehydes 20 with trialkylsilyl triflates 1 in the presence of triethylamine (4) at room temperature yield the silyl enol ethers 3, 7, 9, 11, and 21.The silylation of the unsymmetrical ketones 12 with 1a/4 runs regioselectively in the thermodynamical sense using 1a/12 in excess and yields the enol ethers 13t.The course of this reaction is discussed briefly.
- Emde, Herbert,Goetz, Andreas,Hofmann, Karin,Simchen, Gerhard
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p. 1643 - 1657
(2007/10/02)
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