- Homolytic carbostannylation of alkenes and alkynes with tributylstannyl enolates
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matrix presented In the presence of AIBN, tributylstannyl enolates derived from aromatic ketones reacted with electron-deficient alkenes and a variety of alkynes to give the corresponding carbostannylated adducts. The reactions with methyl acrylate gave α-tributylstannylmethyl-γ-ketoesters, unlike the known Michael-type reaction of stannyl enolates forming δ-ketoesters. The carbostannylation of alkynes proceeded in an anti addition mode to afford β,γ-unsaturated ketones. The reactivity of stannyl enolates as radical transfer agents could be utilized for radical cyclization of 1,6-enynes.
- Miura, Katsukiyo,Saito, Hiroshi,Fujisawa, Naoki,Wang, Di,Nishikori, Hisashi,Hosomi, Akira
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- Visible-Light-Promoted Synthesis of α-CF2H-Substituted Ketones by Radical Difluoromethylation of Enol Acetates
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An efficient and novel visible-light-promoted radical difluoromethylation of enol acetates for the synthesis of α-CF2H-substituted ketones has been described. Upon irradiation under blue LED with catalytic amounts of fac-Ir(ppy)3, this photocatalytic procedure employs difluoromethyltriphenylphosphonium bromide as a radical precursor. Various α-CF2H-substituted ketones are successfully created via designed systems based on the SET process. The methodology has also provided an operationally simple process with broad functional group compatibility.
- Cheng, Li,Dong, Bingbing,Feng, Zengqiang,Li, Yunpu,Wang, Zechao,Wu, Junliang,Zhu, Baoxiang
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supporting information
p. 508 - 513
(2021/01/13)
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- Synthesis of 1,4-Dicarbonyl Compounds by Visible-Light-Mediated Cross-Coupling Reactions of α-Chlorocarbonyls and Enol Acetates
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Herein, we report a protocol for visible-light-mediated radical coupling reactions of α-chloroketones and enol acetates to afford 1,4-dicarbonyl compounds, which are important precursors and intermediates in organic synthesis. The reaction involves photoredox-catalyzed activation of the α-chloroketone upon photoelectron transfer, carbon–chlorine bond cleavage, and coupling of the resulting radical with the carbon–carbon double bond of the enol acetate. This mild protocol has a wide substrate scope and moderate to good yields. (Figure presented.).
- Liu, Qiang,Wang, Rui-Guo,Song, Hong-Jian,Liu, Yu-Xiu,Wang, Qing-Min
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supporting information
p. 4391 - 4396
(2020/09/21)
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- Carboxylic acid addition to terminal alkynes utilizing ammonium tagged Hoveyda-Grubbs catalyst supported on magnetically separable core/shell silica: A highly reusable and air compatible catalytic system
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In this study, the performance of ammonium tagged Hoveyda-Grubbs catalyst supported on magnetically separable core/shell silica gel was tested on carboxylic acid addition reactions to terminal alkynes using a variety of carboxylic acid derivatives under air atmosphere. The catalytic system was found to be compatible with air atmosphere and can tolerate even non-degassed solvents. The reaction parameters such as temperature, substrate/catalyst ratio and the effect of carboxylic acid on the selectivity and yield of the reaction were investigated in details. The reaction of arylacetylenes with acetic acid yielded the corresponding E-isomer with conversion values up to 99% with a catalytic loading of 1% Ru. The reusability of the catalyst was tested using acetic acid/benzoic acid and phenylacetylene in toluene at 85 °C under air atmosphere. The catalyst was found to be highly reusable and maintained its activity up to 11th run, reaching a conversion value of 83% with minimum ruthenium leaching.
- ?ztürk, Bengi ?zgün,Gürcü, Didar,?ehito?lu, Solmaz Karabulut
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- Visible light induced C-H monofluoroalkylation to synthesize 1,4-unsaturated compound
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We developed a method to synthesize fluorinated 1,4-unsaturated dicarbonyl compounds via photoredox catalyzed radical addition process. Commercially available ethyl bromodifluoroacetate (BrCF2CO2Et) as fluoroalkyl source, the corresponding fluoro-containing dicarbonyl compounds could be obtained in moderate to good yields.
- Li, Wei-peng,Zhu, Yu-cheng,Zhou, Yan-jun,Yang, Hong-wei,Zhu, Cheng-jian
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p. 1647 - 1651
(2019/01/22)
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- Reductive Coupling between C-N and C-O Electrophiles
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The cross-electrophile reaction is a promising strategy for C-C bond formation. Recent studies have focused mainly on reactions with organic halides. Here we report a coupling reaction between C-N and C-O electrophiles that demonstrates the possibility of constructing a C-C bond via C-N and C-O cleavage. Several reactions between benzyl/aryl ammonium salts and vinyl/aryl C-O electrophiles have been studied. Preliminary mechanistic studies revealed that the benzyl ammoniums were activated through a radical mechanism.
- He, Rong-De,Li, Chun-Ling,Pan, Qiu-Quan,Guo, Peng,Liu, Xue-Yuan,Shu, Xing-Zhong
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supporting information
p. 12481 - 12486
(2019/09/04)
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- Ag2CO3-mediated direct functionalization of alkyl nitriles: Facile synthesis of γ-ketonitriles through nitrile alkylation of enol acetates
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Direct C(sp3)-H functionalization of alkyl nitriles is a low toxic and facile route to nitrile-containing compounds. In this research, the Ag2CO3-mediated nitrile methylenation of enol acetates is developed to prepare γ-ketonitriles through the direct C(sp3)-H oxidative functionalization of acetonitrile. A radical pathway is proposed, and acetonitrile serves both as solvent and CN-containing radical source.
- Cheng, Pi,Wang, Wei,Wang, Lin,Zeng, Jianguo,Reiser, Oliver,Liang, Yun
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p. 1408 - 1412
(2019/05/06)
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- Salicylic Acid-Catalyzed Arylation of Enol Acetates with Anilines
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α-Aryl ketones are both structure moieties commonly found in bioactive compounds and versatile synthetic intermediates for the preparation of drug-like molecules. An operationally simple and scalable protocol has been developed to prepare α-aryl ketones from readily available aromatic amines and enol acetates (or silyl enol ethers). This metal-free methodology features the use of salicylic acid as a convenient catalyst to promote the formation of aryl radicals from in-situ generated aryl diazonium salts, without demanding thermal or photochemical activation. The mild reaction conditions used are compatible with anilines substituted with diverse functionalities. Structural elaboration of some prepared α-aryl ketones was accomplished to illustrate their usefulness as building blocks. (Figure presented.).
- Felipe-Blanco, Diego,Gonzalez-Gomez, Jose C.
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supporting information
p. 2773 - 2778
(2018/07/29)
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- Synthesis of 1,4-Diketones from β-Oxo Esters and Enol Acetates by Cerium-Catalyzed Oxidative Umpolung Reaction
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Cyclic β-oxo esters are converted with enol acetates in a cerium-catalyzed, oxidative Umpolung reaction to furnish 1,4-diketones with up to 95 % yield. Atmospheric oxygen is the oxidant in this process, which can be regarded as ideal from economic and ecological points of view. Further advantages of this new C-C coupling reaction are its operational simplicity and the application of nontoxic and inexpensive CeCl3·7H2O as precatalyst.
- Geibel, Irina,Christoffers, Jens
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supporting information
p. 918 - 920
(2016/03/01)
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- Iron-Catalyzed Cross-Coupling of Alkenyl Acetates
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Stable C-O linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong C-O bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 C, 2 h) with a ligand-free catalyst (1-2 mol%). Iron clad: Acetates are underutilized electrophiles in metal-catalyzed cross-coupling reactions because of the strong alkenyl C-O bond and their propensity to engage in unwanted reactions. Combination of a ligand-free low-valent Fe catalyst with nucleophilic organomagnesium reagents, low temperature, and short reaction times results in highly selective cross-couplings with alkenyl acetates.
- G?rtner, Dominik,Stein, André Luiz,Grupe, Sabine,Arp, Johannes,Von Wangelin, Axel Jacobi
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supporting information
p. 10545 - 10549
(2015/09/02)
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- A family of low molecular-weight, organic catalysts for reductive C-C bond formation
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Hydrazines form a new family of low molecular-weight reducing agents for diazonium salts. Using only small amounts of hydrazine catalyst, the coupling of diazonium salts to a variety of reactive partners has been achieved, without the requirement for either metal adjuvants or irradiation with visible or ultraviolet light. The generality of the concept proposed herein as well as its advantages in the preparative scale is outlined and discussed.
- Shaaban, Saad,Jolit, Ana?s,Petkova, Desislava,Maulide, Nuno
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supporting information
p. 13902 - 13905
(2015/09/15)
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- Highly efficient Cu(I)-catalyzed trifluoromethylation of aryl(heteroaryl) enol acetates with CF3 radicals derived from CF3SO 2Na and TBHP at room temperature
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An efficient method for the Cu(I)-catalyzed synthesis of α-trifluoromethyl ketones via the addition of CF3 to aryl(heteroaryl) enol acetates by using the readily available CF 3SO2Na (Langlois reagent) has been developed. The reaction is experimentally simple and carried out at room temperature, providing good to excellent yields with wide functional group tolerance.
- Lu, Yang,Li, Yaming,Zhang, Rong,Jin, Kun,Duan, Chunying
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p. 128 - 133
(2014/05/06)
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- Modular P-OP ligands in rhodium-mediated asymmetric hydrogenation: A comparative catalysis study
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Highly efficient and enantioselective hydrogenation reactions for α-(acylamino)acrylates, itaconic acid derivatives and analogues, α-substituted enol ester derivatives, and α-arylenamides (25 substrates) catalyzed by chiral cationic rhodium complexes of a set of P-OP ligands have been developed. The catalytic systems derived from these P-OP ligands provided a straightforward access to enantiomerically enriched α-amino acid, carboxylic acid, amine, and alcohol derivatives that are valuable chiral building blocks. Excellent efficiencies (full conversion in all cases) and extremely high enantiomeric excesses (94-99% ee) were achieved for a wide range of α-substituted enol ester derivatives, regardless of the substitution pattern. The R-oxy group of the ligand (methoxy or triphenylmethoxy) strongly influences the enantioselectivity and catalytic activity. Greater steric bulk around the metal centre correlated to greater (or similar) enantioselectivity, but also to slower hydrogenation. Furthermore, the hydrogenation rates observed with the four model substrates follow the same trend, independently of the R-oxy group of the ligand: methyl 2-acetamidoacrylate>dimethyl itaconate>1-phenylvinyl acetate>N-(1- phenylvinyl)acetamide. A substrate-to-catalyst ratio (S/C) of up to 10,000:1 was sufficient for total hydrogenation of a model substrate of intermediate reactivity (dimethyl itaconate), and did not imply any loss in conversion or enantioselectivity. Copyright
- Nunez-Rico, Jose L.,Etayo, Pablo,Fernandez-Perez, Hector,Vidal-Ferran, Anton
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supporting information
p. 3025 - 3035
(2013/01/15)
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- Visible-light-mediated α-arylation of enol acetates using aryl diazonium salts
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Visible light mediates efficiently the α-arylation of enol acetates by aryl diazonium salts under mild conditions using [Ru(bpy)3]Cl 2 as a photoredox catalyst. The broad scope of the reaction toward various diazonium salts and enol acetates was explored. The application of this reaction in the concise synthesis of 2-substituted indoles was demonstrated
- Hering, Thea,Hari, Durga Prasad,Koenig, Burkhard
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p. 10347 - 10352
(2013/01/15)
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- Selective cine substitution of 1-arylethenyl acetates with arylboron reagents and a diene/rhodium catalyst
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When the crowd says Bo: A carbon-carbon bond is selectively formed at the β position of 1- arylethenyl acetate when the alkenyl substrate is reacted with arylboronic acids in the presence of a cycloocta-1,5-diene/rhodium catalyst. The choice of the ligand is crucial for the unusual cine substitution. Copyright
- Yu, Jung-Yi,Shimizu, Ryosuke,Kuwano, Ryoichi
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supporting information; experimental part
p. 6396 - 6399
(2010/11/17)
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- Direct functionalization of benzylic C-Hs with vinyl acetates via Fe-catalysis
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Direct cross-coupling to construct sp3 C-sp3 C bonds via Fe-catalyzed benzylic C-H activation with 1-aryl vinyl acetate was developed.
- Song, Chun-Xiao,Cai, Gui-Xin,Farrell, Thomas R.,Jiang, Zhong-Ping,Li, Hu,Gan, Liang-Bing,Shi, Zhang-Jie
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supporting information; experimental part
p. 6002 - 6004
(2010/11/16)
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- Utilization of unsaturated esters as perfuming ingredients
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A compound of formula wherein the symbol R′ represents a linear or branched, unsaturated or saturated hydrocarbon group having from 1 to 5 carbon atoms; R1, R2, R3, R4 and R5 represent, independently of each other, a hydrogen atom, a methyl, an ethyl or a methoxy group; R6 and R7 represent, independently of each other, a hydrogen atom, a methyl, ethyl, n-propyl or iso-propyl group; and wherein R5 and R6, when taken together with the carbon atoms to which they are bound, may form a six-membered ring, is useful as perfuming ingredient for the preparation of perfuming compositions and perfumed products, to which it imparts odor notes of the floral and indol type without coloring problems in the final product.
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