- Electrochemical Oxidative Functionalization of Arylalkynes: Access to α,α-Dibromo Aryl Ketones
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A general and effective protocol to synthesize α,α-dibromo aryl ketones has been developed via an electrochemical oxidative method. The reaction proceeds smoothly at room temperature in an undivided cell without the addition of external oxidants. In the reaction process, LiBr acts as both bromine source and supporting electrolyte. This electrooxidation strategy has good substrate applicability and functional group compatibility. Moreover, the reaction could be scaled up efficiently in a continuous flow cell. The target product could undergo further functionalization for the synthesis of some useful heterocyclic compounds. (Figure presented.).
- Wang, Dan,Wan, Zhaohua,Zhang, Heng,Lei, Aiwen
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supporting information
p. 1022 - 1027
(2020/12/31)
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- Method for preparing alpha,alpha-dihalogenated acetophenone compound
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The invention belongs to the technical field of organic synthesis and in particular relates to a method for preparing an alpha,alpha-dihalogenated acetophenone compound. The preparation method provided by the invention comprises the following steps: in an alcohol solvent, enabling nitroalkenes, electrophilic halogen reagents and sodium hydride to react at 55-65 DEG C under a heating condition for5-10 hours, cooling the components to the room temperature, adding a diluted acid solution, and performing continue stirring for 2-5 hours, so as to obtain a target compound, namely alpha,alpha-dihalogenated acetophenone. The method for preparing the alpha,alpha-dihalogenated acetophenone compound, which is provided by the invention, is simple and efficient, mild in condition, easy in raw materialobtaining, green and environment-friendly and simple and convenient to operate, and as a synthesis intermediate, the obtained alpha,alpha-dihalogenated acetophenone compound has the potential of being widely used in fields such as medicine chemical engineering.
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-
Paragraph 0039-0044
(2020/02/04)
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- Switchable Synthesis of α,α-Dihalomethyl and α,α,α-Trihalomethyl Ketones by Metal-Free Decomposition of Enaminone C=C Double Bond
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The novel free radical-based cleavage of the enaminone C=C double bond is realized by using N-halosuccinimides (NXS) in the presence of benzoyl peroxide (BPO) with mild heating, enabling the tunable synthesis of α,α-dihalomethyl ketones and α,α,α-trihalomethyl ketones under different reaction conditions. The formation of these divergent products involving featured C=C double bond cleavage requires no any metal reagent, and represents one more practical example on the synthesis of poly halogenated methyl ketones via the functionalization of carbon?carbon bond. (Figure presented.).
- Liu, Yunyun,Xiong, Jin,Wei, Li,Wan, Jie-Ping
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supporting information
p. 877 - 883
(2020/01/24)
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- Electrochemical synthesis of α,α-dihaloacetophenones from terminal alkyne derivatives
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By virtue of electrochemistry, a series of α,α-dihaloacetophenones were easily obtained with good to excellent yields. This electrochemical procedure was taken in a divided cell with constant current in aqueous media. The reaction can be carried out smoothly at room temperature under metal and oxidant free condition, which provides an eco-friendly synthesis for the α,α-dihaloacetophenone derivatives.
- Li, Zhibin,Sun, Qi,Qian, Peng,Hu, Kangfei,Zha, Zhenggen,Wang, Zhiyong
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supporting information
p. 1855 - 1858
(2020/03/10)
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- Electrochemical Oxidative Oxydihalogenation of Alkynes for the Synthesis of α,α-Dihaloketones
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An electrochemical oxydihalogenation of alkynes has been developed for the first time. Using this sustainable protocol, a variety of α,α-dihaloketones can be prepared with readily available CHCl3, CH2Cl2, ClCH2CH2Cl, and CH2Br2 as the halogen source under electrochemical conditions at room temperature.
- Meng, Xiangtai,Zhang, Yu,Luo, Jinyue,Wang, Fei,Cao, Xiaoji,Huang, Shenlin
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supporting information
p. 1169 - 1174
(2020/02/04)
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- Carbonyl dibromo compound, as well as preparation method and application thereof
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The invention belongs to the technical field of synthetic chemistry, and discloses a carbonyl dibromo compound, as well as a preparation method and an application thereof. The carbonyl dibromo compound has a chemical structural general formula as shown in the specification, wherein R is aryl, substituted aryl, heteroaryl, substituted heteroaryl, paraffin, substituted alkyl or silicyl, wherein thesubstituent group of the substituted aryl, substituted heteroaryl and substituted alkyl is more than one of halogen, alkyl, halogenated alkyl, alkoxy, nitryl, hydroxy, cyan, ester, carbonyl or amide;the heteroaryl is an aromatic ring containing nitrogen, oxygen or sulfur or derivatives thereof. According to the carbonyl dibromo compound, an alkyne compound and sodium bromide are used as raw materials, a high-iodine reagent is used as a catalyst and oxidant, the carbonyl dibromo compound is generated from the alkyne compound. The method has the advantages of mild reaction condition, no heatingrequirement, simple operation steps, high selectivity and high yield, and is safe, reliable and environment-friendly.
- -
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Paragraph 0034-0036
(2019/03/08)
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- Preparation of a novel bromine complex and its application in organic synthesis
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Although molecular bromine (Br2) is a useful brominating reagent, it is not easy to handle. Herein, we describe the preparation of a novel air-stable bromine complex prepared from 1,3-dimethyl-2-imidazolidinone (DMI) and Br2, which was identified to be (DMI)2HBr3 by spectral and X-ray techniques. This complex was then used to brominate olefins, carbonyl compounds, and aromatics, as well as in the Hofmann rearrangement. Yields of reaction products using this complex were almost the same or superior to those using other bromine alternatives.
- Nishio, Yuya,Yubata, Kotaro,Wakai, Yutaro,Notsu, Kotaro,Yamamoto, Katsumi,Fujiwara, Hideki,Matsubara, Hiroshi
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p. 1398 - 1405
(2019/02/07)
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- Highly efficient recyclable sol gel polymer catalyzed one pot difunctionalization of alkynes
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Amino-bridged gel polymer P1 was discovered to catalyze alkyne halo-functionalization in excellent yields, regioselectivity, functional group compatibility, and recyclability. We have observed that both aromatic and aliphatic alkynes can be converted to α,α-dihalogenated ketones in the presence of polymer P1 under metal-free conditions at room temperature within a short reaction time.
- Domena, Justin,Chong, Carlos,Johnson, Qiaxian R.,Chauhan, Bhanu P. S.,Xing, Yalan
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supporting information
(2018/08/17)
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- Micelle-Enabled Photoassisted Selective Oxyhalogenation of Alkynes in Water under Mild Conditions
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Using micelles of FI-750-M, visible light, photocatalysts, and inexpensive halogenating reagents, such as N-bromosuccinimide and N-chlorosuccinimde, selective oxyhalogenations of alkynes were achieved in water under very mild conditions. No halogenation at the aromatic rings was detected, and control experiments revealed the radical pathway. The easily conducted protocol exhibited high reproducibility, was readily adjusted to gram scale, and allowed for recycling of reaction medium and catalyst.
- Finck, Lucie,Brals, Jeremy,Pavuluri, Bhavana,Gallou, Fabrice,Handa, Sachin
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p. 7366 - 7372
(2018/07/29)
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- Directing group assisted copper-mediated aroylation of phenols using 2-bromoacetophenones
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A new directing group assisted method for the synthesis of aryl esters is described. In this Cu(ii)-mediated reaction, 2-formylphenols and 2-acetylphenols are easily converted into aryl esters via treatment with a new aroylating agent 2-bromoacetophenone.
- Baruah, Swagata,Borthakur, Somadrita,Gogoi, Sanjib
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supporting information
p. 9133 - 9135
(2017/08/17)
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- Water-controlled selective preparation of α-mono or α,α′-dihalo ketones: Via catalytic cascade reaction of unactivated alkynes with 1,3-dihalo-5,5-dimethylhydantoin
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The control of a reaction that can produce multiple products from the same starting material is a highly attractive and challenging concept in organic synthesis. An efficient protocol for the selective synthesis of α-mono or α,α′-dihalo ketones via a water-controlled three-component thiourea-catalyzed cascade reaction of unactivated alkynes, 1,3-dihalo-5,5-dimethylhydantoin and water has been developed. α-Monohaloketones were obtained in aqueous acetone at 45 °C; conversely, α,α′-dihalo ketones were formed with pure water as the sole solvent at room temperature.
- Wu, Chao,Xin, Xiu,Fu, Zhi-Min,Xie, Long-Yong,Liu, Kai-Jian,Wang, Zheng,Li, Wenyi,Yuan, Zhi-Hui,He, Wei-Min
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p. 1983 - 1989
(2017/06/09)
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- CoFe2O4–SiO2–SO3H nanocomposite as a magnetically recoverable catalyst for oxidative bromination of alkynes
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A hybrid catalyst has been prepared by incorporating sulfonic acid onto cobalt ferrite magnetic nanoparticles. The catalyst was successfully applied for rapid (20 min) synthesis of α,α-dibromoketones directly from alkynes and NBS. The reaction works well in the presence of 10 wt% of the catalyst at room temperature to produce the desired products in high yield. The catalyst could be recovered using an external magnet and reused without appreciable change in activity.
- Dutta, Mintu Maan,Rajbongshi, Kamal Krishna,Phukan, Prodeep
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p. 2330 - 2341
(2017/11/15)
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- α,α-dibromoketones as useful precursors in organic synthesis: A simple and efficient synthesis of 2,4-diaryl- 1,2,3-triazoles via oxidative cyclization of bisphenylhydrazones
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α,α-Dibromoacetophenones (1a-1f) on reaction with phenylhydrazine afford corresponding arylglyoxal bisphenylhydrazones (2a-2f). The oxidation of bishydrazones 2a-2f by using copper(II) chloride in acetic acid leads to intramolecular cyclization with the formation of 2,4-diaryl-1,2,3-triazoles (3a-3f). The method for the conversion 1 → 3 has been simplified by developing one-pot procedure without isolation of intermediates 2.
- Arora, Loveena,Sharma, Nisha,Kapoor, Jitander K.
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p. 291 - 296
(2019/01/18)
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- Synthesis of 2-Keto(hetero)aryl Benzox(thio)azoles through Base Promoted Cyclization of 2-Amino(thio)phenols with α,α-Dihaloketones
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An interesting base-promoted protocol for the synthesis of 2-keto(hetero)aryl benzox(thi)azoles has been developed. Starting from commercially available 2-amino(thio)phenols and α,α-dihaloketones, moderate to good yields of the corresponding heterocycles can be achieved. Notably, only EtNH2 was required as the promoter here, and the reaction can be easily performed on a large scale.
- Jiang, Jun,Zou, Huaxu,Dong, Qizhi,Wang, Ruijia,Lu, Linghui,Zhu, Yonggang,He, Weimin
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- TsNBr2mediated oxidative functionalization of alkynes
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A new approach has been developed for oxidative transformation of alkynes by controlled manipulation of TsNBr2mediated process. Alkynes could be readily converted to ketones and α-bromoketones via an oxybromination–debromination sequence. When alkynes are treated successively with TsNBr2, KI and Na2SO3in a mixture of acetone and water at room temperature, corresponding ketones were obtained. On the other hand, treatment of alkynes with TsNBr2and Na2SO3in a mixture of ethyl acetate, acetone and water at room temperature could produce corresponding α-bromoketones. 1-Bromoalkynes could also be synthesized from corresponding alkynes within a very short time using TsNBr2at room temperature. In all cases, excellent yields of corresponding products are obtained.
- Rajbongshi, Kamal Krishna,Hazarika, Debojit,Phukan, Prodeep
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p. 4151 - 4158
(2016/07/06)
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- Iron(III) catalyzed halo-functionalization of alkynes
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Abstract Aromatic and aliphatic alkynes can be halo-functionalized to α,α-dihalodimethyl ketals catalyzed by FeCl3 in excellent yields. MeOH is used as a nucleophilic solvent and N-halosuccinimide as the halogen source for this efficient transformation. The resulting α,α-dibromodimethyl ketals can be converted to the corresponding α,α-dibromoketones by treatment with 8% FeCl3 in silica gel.
- Catano, Bryant,Lee, John,Kim, Claudia,Farrell, David,Petersen, Jeffrey L.,Xing, Yalan
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supporting information
p. 4124 - 4127
(2015/08/03)
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- Silica gel catalyzed α-bromination of ketones using N-bromosuccinimide: An easy and rapid method
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An easy and rapid method for the α-bromination of ketones using N-bromosuccinimide (NBS) catalyzed by silica gel in methanol under reflux conditions was developed. The expected products were formed in excellent isolated yields within a short period of time (5-20 min). Major advantages of the present procedure include use of inexpensive and readily available catalyst, exclusion of pre- and post-chemical treatment of catalyst and use of methanol as solvent instead of ethers and chlorinated solvents.
- Mohan Reddy, Bodireddy,Venkata Ramana Kumar, Velpula,Chinna Gangi Reddy, Nallagondu,Mahender Rao, Siripragada
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p. 179 - 182
(2014/02/14)
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- Bronsted acidic ionic liquid accelerated halogenation of organic compounds with N-halosuccinimides (NXS)
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The Bronsted-Acidic ionic liquid 1-methyl-3-(4-sulfobutyl) imidazolium triflate [BMIM(SO3H)][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS) under mild conditions with short reaction times. Methyl aryl ketones were converted into a-halo and a,a-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of a-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H)][OTf] ionic liquid (IL-A) was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.
- Vrazic, Dejan,Jereb, Marjan,Laali, Kenneth K.,Stavber, Stojan
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- Catalyst-and metal-free rapid functionalizations of alkynes using TsNBr2
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A very rapid (3-12 min) and efficient method has been developed for a one-pot synthesis of α,α-dibromoalkanones and β-bromoenol alkanoates directly from alkynes using N,N-dibromo-p-toluenesulfonamide (TsNBr2). The protocol is embellished with f
- Chawla, Ruchi,Singh, Atulk.,Yadav, Laldhar S.
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p. 1558 - 1562
(2013/08/23)
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- [Cu(dap)2Cl] as an efficient visible-light-driven photoredox catalyst in carbon-carbon bond-forming reactions
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Copper sees the light of day: [Cu(dap)2Cl] proved to be an excellent photoredox catalyst for atom-transfer radical addition reactions, as well as for allylation reactions (see scheme), providing an attractive alternative to commonly used iridium- and ruthenium-based catalysts. Copyright
- Pirtsch, Michael,Paria, Suva,Matsuno, Taisuke,Isobe, Hiroyuki,Reiser, Oliver
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supporting information; experimental part
p. 7336 - 7340
(2012/09/08)
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- Visible-light photoredox catalysis: Dehalogenation of vicinal dibromo-, α-halo-, and α,α-dibromocarbonyl compounds
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vic-Dibromo-, α-halo-, or α,α-dibromocarbonyl compounds can be efficiently dehalogenated using catalytic tris(2,2′-bipyridyl) ruthenium dichloride (Ru(bpy)3Cl2) in combination with 1,5-dimethoxynaphthalene (DMN) and ascorbate as sacrificial electron donor. For this process, a visible light promoted photocatalytic cycle is proposed that involves the reduction of carbon halogen bonds via free radical intermediates.
- Maji, Tapan,Karmakar, Ananta,Reiser, Oliver
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supporting information; experimental part
p. 736 - 739
(2011/03/20)
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- Selective 1,2-dihalogenation and oxy-1,1-dihalogenation of alkynes by N-halosuccinimides
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1,2-Dihalogenation and oxy-1,1-dihalogenation of alkynes by N-halosuccinimides can be selectively realized through using different reaction conditions. α,β-Dihalo alkenes were obtained exclusively using THF as solvent without using any catalyst, while α,α
- Liu, Jinhua,Li, Wenjuan,Wang, Chao,Li, Yao,Li, Zhiping
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supporting information; experimental part
p. 4320 - 4323
(2011/09/12)
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- Facile aerobic photo-oxidative syntheses of α,α- dibromoacetophenones from aromatic alkynes with 48% aq HBr
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We report a useful method for facile aerobic photo-oxidative synthesis of α,α-dibromoacetophenones from aromatic alkynes with 48% aq HBr. This method provides the synthesis of α,α-dibromoacetophenones using inexpensive and easily handled bromine sources,
- Nobuta, Tomoya,Hirashima, Shin-Ichi,Tada, Norihiro,Miura, Tsuyoshi,Itoh, Akichika
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experimental part
p. 4576 - 4578
(2010/10/02)
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- Vanadium-catalyzed oxidative bromination promoted by Br?nsted acid or Lewis acid
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The oxidative bromination of arenes was induced by a vanadium catalyst in the presence of a bromide salt and a Br?nsted acid or a Lewis acid under molecular oxygen, which provides an eco-friendly bromination method as compared with a conventional bromination one with bromine. This catalytic reaction could be applied to the bromination of alkenes and alkynes to give the corresponding vic-bromides. Use of aluminum halide as a Lewis acid in place of a Br?nsted acid was demonstrated to provide a more practical protocol for the oxidative bromination. From ketones, α-bromination products were obtained. AlBr3 was found to serve as both a bromide source and a Lewis acid to induce the bromination smoothly. 51V NMR experiment showed that this catalytic bromination is likely to depend on the redox cycle of a vanadium catalyst under molecular oxygen.
- Kikushima, Kotaro,Moriuchi, Toshiyuki,Hirao, Toshikazu
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experimental part
p. 6906 - 6911
(2010/09/18)
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- Substituent effects on the reaction of β-benzoylalanines with Pseudomonas fluorescens kynureninase
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Kynureninase is a pyridoxal 5′-phosphate-dependent enzyme that catalyzes the hydrolytic cleavage of l-kynurenine to give l-alanine and anthranilic acid. β-Benzoyl-l-alanine, the analogue of l-kynurenine lacking the aromatic amino group, was shown to a good substrate for kynureninase from Pseudomonas fluorescens, and the rate-determining step changes from release of the second product, l-Ala, to formation of the first product, benzoate [Gawandi, V. B., et al. (2004) Biochemistry 43, 3230-3237]. In this work, a series of aryl-substituted β-benzoyl-dl-alanines was synthesized and evaluated for substrate activity with kynureninase from P. fluorescens. Hammett analysis of kcat and kcat/Km for 4-substituted β-benzoyl-dl-alanines with electron-withdrawing and electron-donating substituents is nonlinear, with a concave downward curvature. This suggests that there is a change in rate-determining step for benzoate formation with different substituents, from gem-diol formation for electron-donating substituents to Cβ-Cγ bond cleavage for electron-withdrawing substituents. Rapid-scanning stopped-flow kinetic experiments demonstrated that substituents have relatively minor effects on formation of the quinonoid and 348 nm intermediates but have a much greater effect on the formation of the aldol product from reaction of benzaldehyde with the 348 nm intermediate. Since there is a kinetic isotope effect on its formation from β,β-dideuterio-β-(4-trifluoromethylbenzoyl)-dl- alanine, the 348 nm intermediate is proposed to be a vinylogous amide derived from abortive β-deprotonation of the ketimine intermediate. These results provide additional evidence for a gem-diol intermediate in the catalytic mechanism of kynureninase.
- Kumar, Sunil,Gawandi, Vijay B.,Capito, Nicholas,Phillips, Robert S.
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experimental part
p. 7913 - 7919
(2011/11/06)
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- A facile synthesis of two series of multifunctional carbon compounds from α,α-dihalo ketones using allylsamarium bromide
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The use of allylsamarium bromide to effect two different reactions on the common starting material, a,a-dihalo ketones, is presented. With DMF, α-halo-α-allyl aldehydes were obtained, while α-hydroxy- α-allyl aldehyde acetals were obtained in the presence of NaOMe/MeOH. Georg Thieme Verlag Stuttgart.
- Liu, Xiaodan,Zhang, Songlin,Di, Jucai
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experimental part
p. 2749 - 2755
(2010/01/21)
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- In situ-generated zinc bromide-catalyzed α-bromination of alkanones in water
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α-Bromination of alkanones with bromine catalyzed by in situ-generated zinc bromide from zinc dust and bromine in water is investigated. Bromination with dioxane-dibromide as a source of bromine does not require zinc dust and provides selectively α-mono and α,α-dibromo products in excellent yields when water is used as solvent. Copyright Taylor & Francis Group, LLC.
- Juneja, Satinder K.,Choudhary, Deepak,Paul, Satya,Gupta, Rajive
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p. 2877 - 2881
(2007/10/03)
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- TMS·OTf-Catalyzed α-bromination of carbonyl compounds by N-bromosuccinimide
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Various carbonyl compounds undergo α-bromination reaction under a mild and practical condition utilizing N-bromosuccinimide (NBS), catalyzed by trimethylsilyl trifluoromethanesulfonate (TMS·OTf). This method is also effective for the side-chain bromination of heteroaromatic carbonyl compounds without the ring brominations.
- Guha, Samar Kumar,Wu, Bo,Kim, Beom Soo,Baik, Woonphil,Koo, Sangho
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p. 291 - 293
(2007/10/03)
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- Reaction of silyldihalomethyllithiums with nitriles: Formation of α-keto acylsilanes via azirines and 1,3-rearrangement of silyl group from C to N
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A synthesis of α-keto acylsilanes, where 2-bromo-2H-azirine participates as a key intermediate, is reported. The reaction of silyldibromomethyllithium with aryl nitriles provides α-keto acylsilanes in good yields. Interestingly, silyldichloromethyllithium induces aza-1,3-Brook rearrangement of the silyl group in th reaction with nitriles. The rearrangement enables a three-component coupling reaction in a one-pot operation. Copyright
- Yagi, Kazunari,Tsuritani, Takayuki,Takami, Kazuaki,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 8618 - 8619
(2007/10/03)
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- Microwave-induced selective synthesis of α-bromo and α,α-dibromoalkanones using dioxane-dibromide and silica gel under solvent-free conditions
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Selective synthesis of α-bromo and α,α-dibromoalkanones using dioxane-dibromide and silica gel in solvent-free conditions under microwave irradiation has been reported. The amount of dioxane-dibromide, silica gel and time of irradiation are keys for the selective synthesis of α-bromo and α,α-dibromoalkanones.
- Paul, Satya,Gupta, Varinder,Gupta, Rajive,Loupy, André
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p. 439 - 442
(2007/10/03)
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- The design and synthesis of β-trifluoromethylenol phosphates as potential insecticides
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A new group of compounds, β-trifluoromethylenol phosphates [(RO)2P(O)OCR=CHCF3], has been designed and prepared by several methods. Some of them showed good insecticidal activities. In the molecular structure, the designed leaving group can rearrange to a powerful electrophilic agent, β,β-difluorovinyl ketone, which would be a potential enzyme inhibitor.
- Ding, Yixiang,Huang, Xiaogen
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p. 304 - 308
(2007/10/03)
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- A Convenient Halogenation Procedure for the Preparation of α-Halocarbonyl Compounds
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Except for substituted acetophenones (p-Y-C6H4COCH3, Y=H, Br, CH3O), simple ketones, α-ketoesters and 1,3-diketones reacted smoothly with a preformed homogeneous mixture of hydrochloric acid and potassium permanganate in acetonitrile to give moderate to good yields of the corresponding α-chlorocarbonyl compounds.Mixtures of α-chloro- and α,α-dichlorocarbonyl compounds were obtained for substituted acetophenones.Brominations proceeded similarly with higher yields when the hydrochloric acid was replaced with hydrobromic acid. - Key words: α-chlorocarbonyl compounds; α-bromocarbonyl compounds; potassium permanganate; chlorination; bromination.
- Cheng, Sheng-Fan,Lin, Ching-Shan,Liu, Lilian Kao
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p. 309 - 312
(2007/10/03)
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- Synthesis of Dibromoacetyl Derivatives by Use of Benzyltrimethylammonium Tribromide
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The reaction of acetyl derivatives with double the molar quantity of benzyltrimethylammonium tribromide in dichloromethane-methanol solution at room temperature gave dibromoacetyl derivatives in fairly good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Tokiyama, Hajime,Hirakawa, Takahiro,Okamoto, Tsuyoshi
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p. 2667 - 2668
(2007/10/02)
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- AN UNUSUAL OBSERVATION IN THE SYNTHESIS OF THIOZOLES
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Dibromoacetyl benzene derivatives on condensation with thiourea give 2-amino-4-arylthiazoles instead of the expected 2-amino-4-aryl-5-bromothiazoles.Attempts have been made to find the reaction pathway.
- Ahluwalia, V. K.,Arora, K. K.,Kaur, Gurvinder,Mehta, Bhupinder
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p. 333 - 340
(2007/10/02)
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- LES TRIBROMURES DE PHOSPHONIUMS. AGENTS DE BROMINATION DE SUBSTRATS ORGANIQUES
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The reactivities and selectivities of phosphonium tribromides 1-4 towards ketones and their ketals, in the presence of other functional group reactive toward bromide (free enolic position, activated aromatic ring or double bond), are studied and compared with the trimethyl phenyl ammonium tribromide 5.The abilities of the two kinds of tribromides are similar, with a better selectivity of phosphonium salts toward unsaturated ketones, which is probably induced by the greater stability of the ion-pair in phosphonium salts.They act essentially by the tribromide without specific bond interactions between phosphorus and heteroatom of the substrate.
- Cristau, Henri-Jean,Torreilles, Eliane,Morand, Philippe,Christol, Henri
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p. 357 - 368
(2007/10/02)
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- PHOTOINDUCED ALCOHOLYSIS OF alpha , alpha , alpha -TRIBROMACETOPHENONE TO BENZOYLFORMATE.
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Irradiation of p-substituted alpha , alpha , alpha -tribromoacetophenones (1) in O//2-saturated alcohols (MeOH, prim. and sec. alcohols) afforded a new alcoholysis product, benzoylformate (2), in good yield (75-85%) along with benzoate and radical (reduction) products. Sensitization experiments showed that 2 was derived from the triplet excited 1. Formation of 2 as well as the decomposition rate of 1 were greatly accelerated by oxygen, presumably as a result of the involvement of the normally forbidden S//o yields T//1 transition of 1 due to the oxygen-1 charge transfer complex. Independent synthesis and reaction of possible intermediates in the photoalcoholysis of 1 leading to 2 suggested that 2 was formed from spontaneous (dark) reactions of initial photoalcoholysis product, alpha alpha -dibromo- alpha -alkoxyacetophenone.
- Izawa,Ishiguro,Tomioka
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p. 1490 - 1496
(2007/10/02)
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