- A mild and regioselective method for α-bromination of β-keto esters and 1,3-diketones using bromodimethylsulfonium bromide (BDMS)
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Bromodimethylsulfonium bromide has been found to be an effective and regioselective reagent for α-monobromination of β-keto esters and 1,3-diketones. A wide variety of β-keto esters and 1,3-diketones undergo chemoselective α-monobromination with excellent yields at 0-5 °C or room temperature. The notable advantages of this protocol are no need of chromatographic separation, use of less hazardous reagent than molecular bromine, and no added base, Lewis acid, or other catalyst.
- Khan, Abu T.,Ali, Md. Ashif,Goswami, Papori,Choudhury, Lokman H.
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- Chemoselective bromination of active methylene and methyne compounds by potassium bromide, hydrochloric acid and hydrogen peroxide
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Active methylene and methyne compounds can be chemoselectively brominated in high yields using potassium bromide, hydrochloric acid, and hydrogen peroxide at room temperature. Georg Thieme Verlag Stuttgart.
- Kirihara, Masayuki,Ogawa, Shiho,Noguchi, Takuya,Okubo, Kumiko,Monma, Yoshinari,Shimizu, Ikuko,Shimosaki, Ryuji,Hatano, Akihiko,Hirai, Yoshiro
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Read Online
- Halide and preparation method thereof, composition for preparing halide and halogenating reaction
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The invention provides a halide for a halogenating reaction. The halide is used for providing a halogen in the halogenating reaction, the halide comprises any one of compounds shown in a formula I ora formula II or a formula III, in the formula I or the formula II or the formula III, the R group comprises any one of hydrogen or the halogen or an alkyl group or an aryl group or a nitro group, X comprises any one of F or Cl or Br or I, and M comprises any one of tetra-allkylammonium cation, Li, Na, K, Rb and Cs. The invention further provides a preparation method of the halide, a composition for preparing the halide and the halogenating reaction. Accordingly, normal-temperature and additive-free halogenation on the compounds can be achieved, and then products high in yieldand chemoselectivity are obtained; due to the fact that by-products generated after the halide is subjected to a corresponding reaction is likely to be dissolved into water, the corresponding products are likely to be separated and purified.
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Paragraph 0107-0111; 0169-0173; 0230-0234
(2018/07/30)
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- Iron-Catalyzed Acyl Migration of Tertiary α-Azidyl Ketones: Synthetic Approach toward Enamides and Isoquinolones
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This paper reports that tertiary α-azidyl phenyl ketones can be transformed into enamides by treatment with FeBr2 at elevated temperature in DMF. The reaction proceeds via 1,2-benzoyl migration from α-carbon to the nitrogen atom, accompanied by expulsion of a nitrogen molecule. This protocol is suitable for the synthesis of N-(cyclopent-1-en-1-yl)benzamides, N-(cyclohex-1-en-1-yl)benzamides, and N-benzoyl-α-methyl enamines and provides a convenient approach toward isoquinolones.
- Yang, Tonghao,Fan, Xing,Zhao, Xiaopeng,Yu, Wei
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supporting information
p. 1875 - 1879
(2018/04/16)
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- PPh3·HBr-DMSO: A Reagent System for Diverse Chemoselective Transformations
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The broad applicability of the hitherto unexplored reagent combination PPh3·HBr-DMSO is exemplified with multiple highly diverse one-step transformations to synthetically useful building blocks, such as flavones, 4H-thiochromen-4-ones, α-hydroxy ketones, 1,4-naphthoquinones (including vitamin K3), 2-bromo-3-substituted-1H-1-indenones, 2-methylthio-1H-1-indenones, 3-butyne-1,2-dione, and 4-pentene-2,3-diones. The simple and mild reaction conditions make the reagent superior in terms of yield and substrate scope in comparison with the existing alternatives.
- Mal, Kanchan,Kaur, Amanpreet,Haque, Fazle,Das, Indrajit
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p. 6400 - 6410
(2015/06/30)
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- Novel Metal- and Mineral-Acid-Free Synthesis of Organic Ammonium Tribromides and Application of Ethylenephenanthrolium Bistribromide for Bromination of Active Methylene Group of 1,3-Diketones and β-Ketoesters
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A novel procedure for the preparation of organic ammonium tribromides (OATBs) is described from their corresponding bromides. Quaternary ammonium bromides (QABs) and a N,N′-heterocyclic dibromide are efficiently oxidized to their corresponding monotribromides and bistribromide by m-chloroperbenzoic acid (MCPBA) in the presence of 2 and 4 equiv of KBr, respectively. The reactions are carried out in an aqueous medium without the use of any mineral acid or metal catalyst/promoters. A variety of tribromides are synthesized in very good yields including a hitherto unknown reagent, 1,10-(ethane-1, 2-diyl)phenanthrolinediium bistribromide (EPDBT). EPDBT is investigated as brominating agent and found to be highly effective for selective bromination of active methylene groups of a variety of 1,3-diketones and β-ketoesters. GRAPHICAL ABSTRACT.
- Dey, Rupa Rani,Paul, Bappi,Dhar, Siddhartha Sankar
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supporting information
p. 724 - 736
(2015/10/29)
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- Oxidative bromination of ketones using ammonium bromide and oxone
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A highly efficient, environmentally safe and economic method for selective α-monobromination of aralkyl, cyclic, acyclic, 1,3-diketones and β-keto esters and α,α-dibromination of 1,3-diketones and β-keto esters without catalyst is reported using ammonium bromide as a bromine source and oxone as an oxidant. The reaction proceeds at ambient temperature and yields range from moderate to excellent. Bromination of unsymmetrical ketones takes place at the less substituted α-position predominantly. Aromatisation of tetralones is also carried out with this reagent system.
- MacHarla, Arun Kumar,Chozhiyath Nappunni, Rohitha,Marri, Mahender Reddy,Peraka, Swamy,Nama, Narender
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supporting information; experimental part
p. 191 - 195
(2012/01/17)
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- Sulfoxide-mediated Umpolung of alkali halide salts
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A new protocol for the direct two-electron oxidative Umpolung of alkali halide salts is reported. This procedure, relying on the use of a commercially available sulfoxide as the oxidant, allows the electrophilic halogenation of carbonyl compounds as well as halolactonisation reactions to proceed from the corresponding sodium salts, at room temperature and under mild conditions.
- Klimczyk, Sebastian,Huang, Xueliang,Fares, Christophe,Maulide, Nuno
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supporting information; experimental part
p. 4327 - 4329
(2012/06/29)
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- Facile and efficient method for oc-monobromination of dicarbonyl compounds with N-bromosuccinimide
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The a-monobrominated products were prepared fast in presence of p-TsOH as catalyst in very high yields using various 1,3-diketones and β-keto-esters with N-bromosuccinimide in CH2C12.
- Fang, Li-Zhen,Shen, Jiu-Ming,Lv, Qing-Hua,Yan, Fu-Lin
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experimental part
p. 3425 - 3427
(2012/02/04)
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- Hydrogen peroxide or peracetic acid mediated self-titrating α-halogenation of 1,3-dicarbonyl compounds
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Efficient oxidative -halogenation of 1,3-dicarbonyl compounds has been achieved by employing a system comprising of sub-stoichiometric amounts of TiX4 (X = Cl, Br) in conjunction with environmentally benign hydrogen peroxide (H2Osub
- Akula, Ramulu,Galligan, Marc J.,Ibrahim, Hasim
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experimental part
p. 347 - 351
(2011/03/18)
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- Facile preparation of the synthon of 7-ethyl-8-oxabicyclo[4.3.0]nonane-2,9- dione
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The useful synthon of 7-ethyl-8-oxabicyclo[4.3.0]2,9-dioxononane was readily synthesized by a facile method. Starting from ethyl-1-bromo-2- oxocyclohexane- carboxylate, the 7-ethyl-8-oxabicyclo[4.3.0]nonane-2,9-dione was obtained by subsequent reactions o
- Fang, Li-Zhen,Li, Yong-Hai,Liu, Jing-Ping,Yan, Fu-Lin
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scheme or table
p. 2919 - 2921
(2012/02/02)
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- Umpolung of halide reactivity: Efficient (diacetoxyiodo)benzene-mediated electrophilic α-halogenation of 1,3-dicarbonyl compounds
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An efficient high-yielding (diacetoxyiodo)benzene-mediated α-halogenation of 1,3-dicarbonyl compounds utilising titanium tetrahalides as the halide source has been developed. The Royal Society of Chemistry 2009.
- Akula, Ramulu,Galligan, Marc,Ibrahim, Hasim
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experimental part
p. 6991 - 6993
(2010/04/25)
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- Rapid and catalyst-free α-halogenation of ketones using N-halosuccinamides in DMSO
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α-Halogenation of various carbonyl compounds such as β-keto-esters, cyclic ketones, and lactams with N-halosuccinamides (NBS, NCS, NIS) in the presence of DMSO proceeded very smoothly to give the corresponding α-monohalogenated products in good to excellent yields with high selectivity under catalyst-free conditions. Copyright Taylor & Francis Group, LLC.
- Sreedhar,Reddy, P. Surendra,Madhavi
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p. 4149 - 4156
(2008/03/13)
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- A green approach for efficient α-halogenation of β-dicarbonyl compounds and cyclic ketones using N-halosuccinimides in ionic liquids
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Room temperature ionic liquids (ILs) are used as a green recyclable reaction media for the α-monohalogenation of 1,3-diketones, β-keto-esters and cyclic ketones with N-halosuccinimides in excellent yields in the absence of a catalyst. The recovered ionic liquid was reused five to six times with consistent activity.
- Meshram,Reddy,Vishnu,Sadashiv,Yadav
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p. 991 - 995
(2007/10/03)
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- A mild and environmentally acceptable synthetic protocol for chemoselective α-bromination of β-keto esters and 1,3-diketones
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A wide variety of unsubstituted β-keto esters can be brominated chemoselectively to the corresponding α-monobromo-β-keto esters by using a combination of vanadium pentoxide, hydrogen peroxide and ammonium bromide in a biphasic system, dichloromethane-wate
- Khan, Abu T.,Goswami, Papori,Choudhury, Lokman H.
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p. 2751 - 2754
(2007/10/03)
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- An efficacious method for the halogenation of β-dicarbonyl compounds under mildly acidic conditions
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A variety of 1,3-diketones, β-ketoesters and malonates can be chlorinated in high yields using sodium hypochlorite in a 5:2 mixture of acetone/acetic acid at 0°C for 1 h. Similarly, bromination of these dicarbonyl substrates can be accomplished under the same conditions using sodium hypobromite.
- Meketa, Matthew L.,Mahajan, Yogesh R.,Weinreb, Steven M.
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p. 4749 - 4751
(2007/10/03)
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- Amberlyst-15-promoted efficient 2-halogenation of 1,3-keto-esters and cyclic ketones using N-halosuccinimides
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A simple and rapid process has been developed for the α- monohalogenation of 1,3-keto-esters with N-halosuccinimides catalyzed by Amberlyst-15 at room temperature to produce the corresponding 2-halo 1,3-keto-esters in high yields. This protocol also extended to α-halogenation of cyclic ketones.
- Meshram,Reddy,Sadashiv,Yadav
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p. 623 - 626
(2007/10/03)
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- Radical Chain Reactions of α-Azido-β-keto Esters with Tributyltin Hydride. a Novel Entry to Amides and Lactams through Regiospecific Nitrogen Insertion
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A variety of acyclic and carbocyclic α-azido-β-keto esters have been readily prepared from the parent dicarbonyl compounds, and their radical chain reactions with tributyltin hydride have been investigated. These reactions normally result in efficient production of alkoxycarbonyl-substituted amides and lactams and thence provide a new, useful method for regiospecific nitrogen insertion of keto ester compounds. The likely mechanism entails initial addition of tributylstannyl radical to the azido moiety to give a stannylaminyl radical, which readily undergoes intramolecular three-membered cyclization onto the ketone group to form an alkoxyl radical. The alkoxyl radical then undergoes regiospecific β-scission to form a stable ring-opened radical that is eventually reduced by tributyltin hydride to propagate the chain. With certain substrates, concomitant deazidation occurs to an important extent. This process, which is unusually observed in radical reactions of alkyl azides, is ascribed to addition of the stannyl radical to the terminal azido nitrogen; subsequent fragmentation of the ensuing 1,3-triazenyl adduct gives stannyl azide and a deazidated alkyl radical, resonance-stabilized by the adjacent carbonyl groups. The radical reactions of 2-azido-2-(ethoxycarbonyl)-1-tetralone with allyltributylstannane and allyltriphenylstannane have also been investigated with the (missed) aim to achieve nitrogen insertion and concomitant allylation.
- Benati, Luisa,Nanni, Daniele,Sangiorgi, Corrado,Spagnolo, Piero
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p. 7836 - 7841
(2007/10/03)
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