- Unraveling two pathways for NHPI-mediated electrocatalytic oxidation reaction
-
Two pathways for N-hydroxyphthalimide (NHPI)-mediated electrocatalytic oxidation using phenylacetate derivatives as template substrates were first reported for benzylic C[sbnd]H oxidation to oxygenated and non-oxygenated products. DFT calculation indicates that the hydrogen-atom transfer (HAT) process between phthalimido-N-oxyl (PINO) and substrate is a rate-determined step. Aromatic α-keto esters and 2-((1,3-dioxoisoindolin-2-yl)oxy)-2-aryl acetate obtained by cross-coupling between benzylic radical and PINO can be selectively synthesized through controlling the concentration of PINO radical. This method provides a deep understanding for selective weak C[sbnd]H oxidation using NHPI as redox mediator.
- Xu, Leitao,Yi, Yangjie,Hu, Sideng,Ye, Jiao,Hu, Aixi
-
-
- Photoinduced Diverse Reactivity of Diazo Compounds with Nitrosoarenes
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A diverse reactivity of diazo compounds with nitrosoarene in an oxygen-transfer process and a formal [2 + 2] cycloaddition is reported. Nitosoarene has been exploited as a mild oxygen source to oxidize an in situ generated carbene intermediate under visible-light irradiation. UV-light-mediated in situ generated ketenes react with nitosoarenes to deliver oxazetidine derivatives. These operationally simple processes exemplify a transition-metal-free and catalyst-free protocol to give structurally diverse α-ketoesters or oxazetidines.
- Roy, Sourav,Kumar, Gourav,Chatterjee, Indranil
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p. 6709 - 6713
(2021/09/08)
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- Copper on charcoal: Cu0nanoparticle catalysed aerobic oxidation of α-diazo esters
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By using a charcoal supported nano Cu0catalyst (Cu/C), a highly efficient oxidation of α-diazo esters to α-ketoesters with molecular oxygen as the sole oxidant has been developed. In the presence of the Cu/C catalyst, 2-aryl-α-diazo esters with both electron-donating and electron-withdrawing groups can be oxidized to the corresponding α-ketoesters efficiently. Furthermore, this Cu/C catalyst can catalyse the reaction of aryl α-diazo ester with water to form aryl ketoester, 2-aryl-2-hydroxyl acetate ester and 2-aryl acetate ester. In this case, water is split by α-diazo ester, and the diazo group is displaced by the oxygen or hydrogen atom in water. Mechanistic investigation showed that the reaction of α-diazo ester with oxygen proceeds through a radical pathway. In the presence of 2,2,6,6-tetramethyl piperidine nitrogen oxide, the reaction of α-diazo ester with oxygen is dramatically inhibited. Furthermore, the reaction of α-diazo ester with water is investigated by an isotopic tracer method, and GCMS detection showed that a disproportionation reaction occurred between α-diazo ester and water.
- Chu, Changhu,Dong, Wenwen,Lin, Jia,Teng, Jiangge,Wang, Zhiwei,Zhao, Rong
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p. 6120 - 6126
(2021/07/21)
-
- Carbene-Catalyzed Enantioselective Aromatic N-Nucleophilic Addition of Heteroarenes to Ketones
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The aromatic nitrogen atoms of heteroarylaldehydes are activated by carbene catalysts to react with ketone electrophiles. Multi-functionalized cyclic N,O-acetal products are afforded in good to excellent yields and optical purities. Our reaction involves the formation of an unprecedented aza-fulvene-type acylazolium intermediate. A broad range of N-heteroaromatic aldehydes and electron-deficient ketone substrates works effectively in this transformation. Several of the chiral N,O-acetal products afforded through this protocol exhibit excellent antibacterial activities against Ralstonia solanacearum (Rs) and are valuable in the development of novel agrichemicals for plant protection.
- Liu, Yonggui,Luo, Guoyong,Yang, Xing,Jiang, Shichun,Xue, Wei,Chi, Yonggui Robin,Jin, Zhichao
-
supporting information
p. 442 - 448
(2019/11/25)
-
- Isothiourea-Catalyzed Acylative Kinetic Resolution of Tertiary α-Hydroxy Esters
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A highly enantioselective isothiourea-catalyzed acylative kinetic resolution (KR) of acyclic tertiary alcohols has been developed. Selectivity factors of up to 200 were achieved for the KR of tertiary alcohols bearing an adjacent ester substituent, with both reaction conversion and enantioselectivity found to be sensitive to the steric and electronic environment at the stereogenic tertiary carbinol centre. For more sterically congested alcohols, the use of a recently-developed isoselenourea catalyst was optimal, with equivalent enantioselectivity but higher conversion achieved in comparison to the isothiourea HyperBTM. Diastereomeric acylation transition state models are proposed to rationalize the origins of enantiodiscrimination in this process. This KR procedure was also translated to a continuous-flow process using a polymer-supported variant of the catalyst.
- Greenhalgh, Mark D.,Laina-Martín, Víctor,Neyyappadath, Rifahath M.,Qu, Shen,Smith, Andrew D.,Smith, Samuel M.
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supporting information
p. 16572 - 16578
(2020/09/09)
-
- Copper(I)-catalyzed aerobic oxidation of α-diazoesters
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A practical Cu-catalyzed oxidation of α-diazoesters to α-ketoesters using molecular oxygen as an oxidant has been developed. Both electron-poor and electron-rich aryl α-diazoesters are suitable substrates and provide the α-ketoesters in good yields. In this oxidative system, α-diazo-β-ketoesters are also compatible as substrates but unexpectedly furnish α-ketoesters via C-C bond cleavage, rather than the vicinal tricarbonyl products.
- Xu, Changming,Bai, Lei,Wang, Yongchang
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p. 12579 - 12584
(2020/11/09)
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- Pd(OAc)2-Catalyzed Asymmetric Hydrogenation of α-Iminoesters
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An efficient Pd(OAc)2-catalyzed asymmetric hydrogenation of α-iminoesters was realized for the first time at 1 atm hydrogen pressure and room temperature. Pd(OAc)2, a less expensive Pd salt with low toxicity, was found to be the most suitable catalyst precursor rather than Pd(TFA)2 which is usually the catalyst of choice for homogeneous asymmetric hydrogenation. The chiral α-arylglycine fragments are widely found in many chiral products and bioactive molecules.
- Chen, Jianzhong,Li, Feilong,Wang, Fang,Hu, Yawen,Zhang, Zhenfeng,Zhao, Min,Zhang, Wanbin
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supporting information
p. 9060 - 9065
(2019/11/19)
-
- CuO-catalyzed oxidation of aryl acetates with aqueous tert-butyl hydroperoxide for the synthesis of α-ketoesters
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A practical method to access α-ketoesters from readily available aryl acetates is developed. In this approach, aqueous tert-butyl hydroperoxide and CuO are employed. No additional solvents are required and it was found that the peroxide side products in the reaction can be decomposed by pyridine.
- Jiang, Jin
-
p. 235 - 240
(2019/07/16)
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- Controllable chemoselectivity in the coupling of bromoalkynes with alcohols under visible-light irradiation without additives: Synthesis of propargyl alcohols and α-ketoesters
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The chemoselectivity of visible-light-induced coupling reactions of bromoalkynes with alcohols can be controlled by simple changes to the reaction atmosphere (N2 or O2). A N2 atmosphere favours propargyl alcohols via a direct C-C coupling process, whereas an O2 atmosphere results in the generation of α-ketoesters through the oxidative CC/C-O coupling pathway.
- Ni, Ke,Meng, Ling-Guo,Ruan, Hongjie,Wang, Lei
-
supporting information
p. 8438 - 8441
(2019/07/22)
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- Highly adequate oxidative esterification of α-carbonyl aldehydes with alkyl halides in TBAI/TBHP mediated system
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An efficient and viable synthesis of α-ketoesters from alkyl halides and α-carbonyl aldehydes has been reported under metal-free conditions. The present method involves oxidative esterification of α-carbonyl aldehydes with alkyl halide using TBAI as a promoter and TBHP as an oxidant to form α-ketoesters in good to excellent yields with versatile structural diversity. Use of commercially accessible and inexpensive substrates, broad substrate scope and good functional group tolerance are the key features of this protocol.
- Bhargude, Pooja L.,Lade, Jatin J.,Patil, Bhausaheb N.,Vadagaonkar, Kamlesh S.,Chaskar, Atul C.
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supporting information
p. 1325 - 1333
(2019/04/30)
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- Cobalt-Catalyzed Transfer Hydrogenation of α-Ketoesters and N-Cyclicsulfonylimides Using H2O as Hydrogen Source
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A Co-catalyzed effective transfer hydrogenation of various α-ketoesters and N-cyclicsulfonylimides by safe and environmentally benign H2O as hydrogen source is described. The reaction used easily available and easy to handle zinc metal as a reductant. Interestingly, the catalytic system does not require ligand for reduction of N-cyclicsulfonylimides. (Figure presented.).
- Gao, Yang,Zhang, Xuexin,Laishram, Ronibala Devi,Chen, Jingchao,Li, Kangkui,Zhang, Keyang,Zeng, Guangzhi,Fan, Baomin
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supporting information
p. 3991 - 3997
(2019/08/02)
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- Heterogeneous Esterification from α-Hydroxy Ketone and Alcohols through a Tandem Oxidation Process over a Hydrotalcite-Supported Bimetallic Catalyst
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Heterogeneous aerobic oxidative esterification between α-hydroxy ketone and alcohols catalyzed by a hydrotalcite-supported bimetallic catalyst (CuMn/HT) using O2 as a green oxidant was achieved. Recyclable CuMn/HT exhibits high catalytic activity due to increased content of oxygen vacancies and a newly generated CuMn2O4 crystal phase. This clean esterification proceeds through a tandem oxidation process in the absence of any additives and ligands and affords α-keto esters in good to excellent yields. Moreover, the catalytic system tolerates complicated bioactive molecules as raw materials and can be performed on a multigram scale.
- Meng, Xu,Bi, Xiuru,Chen, Gexin,Chen, Baohua,Zhao, Peiqing
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p. 1716 - 1722
(2018/10/25)
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- Copper catalyzed photoredox synthesis of α-keto esters, quinoxaline, and naphthoquinone: Controlled oxidation of terminal alkynes to glyoxals
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Herein, we report a facile visible light induced copper catalyzed controlled oxidation of terminal CC alkynes to α-keto esters and quinoxalines via formation of phenylglyoxals as stable intermediates, under mild conditions by using molecular O2 as a sustainable oxidant. The current copper catalysed photoredox method is simple, highly functional group compatible with a broad range of electron rich and electron poor aromatic alkynes as well as aliphatic alcohols (1°, 2° and 3° alcohols), providing an efficient route for the preparation of α-keto esters (43 examples), quinoxaline and naphthoquinone with higher yields than those in the literature reported thermal processes. Furthermore, the synthetic utility of the products has been demonstrated in the synthesis of two biologically active molecules, an E. coli DHPS inhibitor and CFTR activator, using the current photoredox process. In addition, we applied this methodology to the one-pot synthesis of a heterocyclic compound (quinoxaline, an FLT3 inhibitor) by trapping the intermediate phenylglyoxal with O-phenylenediamine. The intermediate phenylglyoxal can also be isolated and further reacted with an internal alkyne to form naphthoquinone. This process can be readily scaled up to the gram scale.
- Das, Deb Kumar,Kumar Pampana, V. Kishore,Hwang, Kuo Chu
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p. 7318 - 7326
(2018/10/15)
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- CuCl/TMEDA/nor-AZADO-catalyzed aerobic oxidative acylation of amides with alcohols to produce imides
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Although aerobic oxidative acylation of amides with alcohols would be a good complement to classical synthetic methods for imides (e.g., acylation of amides with activated forms of carboxylic acids), to date, there have been no reports on oxidative acylation to produce imides. In this study, we successfully developed, for the first time, an efficient method for the synthesis of imides through aerobic oxidative acylation of amides with alcohols by employing a CuCl/TMEDA/nor-AZADO catalyst system (TMEDA = teramethylethylendiamine; nor-AZADO = 9-azanoradamantane N-oxyl). The proposed acylation proceeds through the following sequential reactions: aerobic oxidation of alcohols to aldehydes, nucleophilic addition of amides to the aldehydes to form hemiamidal intermediates, and aerobic oxidation of the hemiamidal intermediates to give the corresponding imides. This catalytic system utilizes O2 as the terminal oxidant and produces water as the sole by-product. An important point for realizing this efficient acylation system is the utilization of a TMEDA ligand, which, to the best of our knowledge, has not been employed in previously reported Cu/ligand/N-oxyl systems. Based on experimental evidence, we consider that plausible roles of TMEDA involve the promotion of both hemiamidal oxidation and regeneration of an active CuII-OH species from a CuI species. Here promotion of hemiamidal oxidation is particularly important. Employing the proposed system, various types of structurally diverse imides could be synthesized from various combinations of alcohols and amides, and gram-scale acylation was also successful. In addition, the proposed system was further applicable to the synthesis of α-ketocarbonyl compounds (i.e., α-ketoimides, α-ketoamides, and α-ketoesters) from 1,2-diols and nucleophiles (i.e., amides, amines, and alcohols).
- Kataoka, Kengo,Wachi, Keiju,Jin, Xiongjie,Suzuki, Kosuke,Sasano, Yusuke,Iwabuchi, Yoshiharu,Hasegawa, Jun-Ya,Mizuno, Noritaka,Yamaguchi, Kazuya
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p. 4756 - 4768
(2018/06/07)
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- Visible Light Promotes Decyanation Esterification Reaction of β - Ketonitriles with Dioxygen and Alcohols to α-Ketoesters
-
A green and mild method has been developed for the conversion of β-ketonitriles into α-ketoesters under catalyst-free conditions. A plausible mechanism is that visible light promotes singlet oxygen generation to form the products through oxidative C-H bond functionalization and C-C σ -bond cleavage.
- Xu, Chen,Zhang, Nan-Nan,Li, Xiao-Ji,Ge, Yan-Qin,Diao, Pin-Hui,Guo, Cheng
-
supporting information
p. 1065 - 1070
(2018/05/01)
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- Diastereo- and Enantioselective Synthesis of Fluorine Motifs with Two Contiguous Stereogenic Centers
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The synthesis of chiral fluorine containing motifs, in particular, chiral fluorine molecules with two contiguous stereogenic centers, has attracted much interest in research due to the limited number of methods available for their preparation. Herein, we report an atom-economical and highly stereoselective synthesis of chiral fluorine molecules with two contiguous stereogenic centers via azabicyclo iridium-oxazoline-phosphine-catalyzed hydrogenation of readily available vinyl fluorides. Various aromatic, aliphatic, and heterocyclic systems with a variety of functional groups were found to be compatible with the reaction and provide the highly desirable product as single diastereomers with excellent enantioselectivities.
- Ponra, Sudipta,Rabten, Wangchuk,Yang, Jianping,Wu, Haibo,Kerdphon, Sutthichat,Andersson, Pher G.
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supporting information
p. 13878 - 13883
(2018/10/24)
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- I 2 /TBHP-Promoted Approach to α-Keto Esters from Trifluoromethyl β-Diketones and Alcohols via C-C Bond Cleavage
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A metal-free oxidative coupling reaction of trifluoromethyl β-diketones with alcohols for the synthesis of α-keto esters in good to excellent yields has been developed. Preliminary mechanistic studies suggest that an I 2 /TBHP promoted sequential iodination, C-C bond cleavage, C-O bond formation and oxidation pathway is involved in this reaction.
- Shao, Tongle,Fang, Xiang,Zhou, Jun,Jin, Chen,Yang, Xueyan,Wu, Fanhong
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supporting information
p. 2018 - 2023
(2017/09/13)
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- A method for synthesis of α - keto ester
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A synthetic method of [alpha]-keto ester. The invention relates to the technical field of chemical synthesis. The synthetic method comprises a step of in a solvent, with benzene seleninic acid as a catalyst and air as an oxidizing agent, oxidizing [alpha]-hydroxy acid ester to obtain an oxidized product [alpha]-keto ester. In the method, air is employed as the oxidizing agent, which is clean, is easy to obtain, and is harmless to environment. The method employs the benzene seleninic acid as the catalyst instead of a metal catalyst, so that the [alpha]-keto ester is metabolizable in human body and is ecological friendly since selenium is required microelement of living bodies. The synthetic method is carried out under mild conditions and is less in damage on devices. A system for the method is durable, so that the method is suitable for industrial production.
- -
-
Paragraph 0036-0038
(2017/08/25)
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- Novel Synthesis of α-Keto Esters and Amides by an sp3 C-H Oxidation of Nitromethyl Aryl Ketones Promoted by Ion-Supported (Diacetoxyiodo)benzene
-
A simple and efficient method is described for the preparation of α-keto esters or amides from nitromethyl aryl ketones. In the presence of nucleophiles (alcohols or amines), the ion-supported (di-acetoxyiodo)benzene-promoted sp3 C-H oxidation of nitromethyl aryl ketones proceeded efficiently under mild conditions to give the corresponding α-keto esters and amides in moderate to good yields. This is the first reported use of (diacetoxyiodo)benzene in the synthesis of α-keto esters and amides. The reaction is ecofriendly and has the -advantages of mild conditions, short reaction times, and a recyclable reagent.
- Jiang, Xiaoying,Gan, Bing,Liu, Jiwei,Xie, Yuanyuan
-
supporting information
p. 2737 - 2741
(2016/11/25)
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- Metal-free oxidative esterification of acetophenones with alcohols: A facile one-pot approach to α-ketoesters
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A novel and efficient oxidative esterification method for the synthesis of α-ketoesters has been developed under mild and environmentally benign conditions, which is a facile one-pot approach to α-ketoesters from commercially available acetophenones with alcohols, especially under metal-free conditions, with broad substrate scope. A possible mechanism is proposed on the basis of a series of control experiments and DMSO18 isotopic labelling experiments.
- Guo, Shiyu,Dai, Zhongxue,Yang, Zhao,Zhu, Ning,Wan, Li,Li, Xin,Liu, Chengkou,Fang, Zheng,Guo, Kai
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p. 98422 - 98426
(2016/10/31)
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- Iron-Catalyzed Esterification of Benzyl C-H Bonds to Form α-Keto Benzyl Esters
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An atom-economic and efficient non-precious metal-catalyzed esterification of benzyl C-H bonds has been developed. A variety of α-keto benzyl esters have been accessed in good yields through the reactions between benzyl derivatives and benzoylformic acids using iron trifluoride as a catalyst in the presence of di-tert-butyl peroxide under an inert atmosphere. This strategy provides a straightforward access to linearly expanded α-keto benzyl esters. A plausible reaction mechanism is proposed.
- He, Yue,Mao, Jincheng,Rong, Guangwei,Yan, Hong,Zhang, Guoqi
-
supporting information
p. 2125 - 2131
(2015/06/23)
-
- A novel method for synthesis of α-keto esters with phenyliodine(III) diacetate
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A rapid and efficient synthesis of α-keto esters from β-ketonitriles using phenyliodine(III) diacetate is reported. This protocol gave α-keto esters in good yields. This is the first time to report the application of hypervalent iodine(III) reagents in the synthesis of α-keto esters. A plausible reaction mechanism is proposed.
- Xie, Yuanyuan,Liu, Jiwei,Huang, Yingyi,Yao, Lixia
-
supporting information
p. 3793 - 3795
(2015/06/08)
-
- Cu-catalyzed aerobic oxidative esterification of acetophenones with alcohols to ?±-ketoesters
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Copper-catalyzed aerobic oxidative esterification of acetophenones with alcohols using molecular oxygen has been developed to form a broad range of ?±-ketoesters in good yields. In addition to reporting scope and limitations of our new method, mechanism studies are reported that reveal that the carbonyl oxygen in the ester mainly originated from dioxygen.
- Xu, Xuezhao,Ding, Wen,Lin, Yuanguang,Song, Qiuling
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supporting information
p. 516 - 519
(2015/03/03)
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- Organocatalytic Enantioselective Michael Reaction of Malononitrile with β,β-Disubstituted Nitroalkenes
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We have developed and optimized an enantioselective Michael reaction of malononitrile with β,β-disubstituted nitroalkenes. This reaction was catalyzed by a cinchona alkaloid derived thiourea catalyst, producing products of high yields (up to 98 %) and ste
- Chen, Shengwei,Lou, Qinxin,Ding, Yuyang,Zhang, Shasha,Hu, Wenhui,Zhao, Junling
-
supporting information
p. 2437 - 2441
(2015/08/18)
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- Amino Acid Salt Catalyzed Asymmetric Synthesis of 1,2-Diols with A Quaternary Carbon Center
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Enantioenriched 1,2-diols with a quaternary carbon center have great potential in the preparation of natural and biologically active compounds, but remain challenging synthetic targets which demand for both good diastereo- and enantioselectivity. As part
- Wu, Quanquan,Liu, Shulei,Wang, Fangyuan,Li, Qingqing,Cheng, Kangli,Li, Juan,Jiang, Jun
-
supporting information
p. 2442 - 2446
(2015/10/19)
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- First Iridium-Catalyzed Highly Enantioselective Hydrogenation of β-Nitroacrylates
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The first highly chemo- and enantioselective hydrogenation of β-nitroacrylates was accomplished with an iridium catalyst (Ir-4) with yields and enantioselectivities of up to 96% and 98% ee, respectively. The resulting α-chiral β-nitro propionates are attractive building blocks for the synthesis of chiral β2-amino acids, which are the core scaffolds of bioactive natural products, pharmaceuticals, and β-peptides.
- Li, Shengkun,Xiao, Taifeng,Li, Dangdang,Zhang, Xumu
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supporting information
p. 3782 - 3785
(2015/08/18)
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- Metal-free tandem oxidative aryl migration and C-C bond cleavage: Synthesis of α-ketoamides and esters from acrylic derivatives
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A novel tandem metal-free oxidative aryl migration/C-C bond-cleavage reaction, mediated by hypervalent iodine reagent, has been discovered. The presented transformation provided straightforward access to important α-ketoamide and α-ketoester derivatives from readily available acrylic derivatives via a concerted process of 1,2-aryl shift concomitant with C-C bond cleavage.
- Liu, Le,Du, Liang,Zhang-Negrerie, Daisy,Du, Yunfei,Zhao, Kang
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supporting information
p. 5772 - 5775
(2015/02/19)
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- I2-promoted cross-dehydrogenative coupling of α-carbonyl aldehydes with alcohols for the synthesis of α-ketoesters
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A facile and efficient method for the synthesis of α-ketoesters from alcohols and α-carbonyl aldehydes has been developed at room temperature under metal-free conditions for the first time. Various alcohols and α-carbonyl aldehydes could participate in this reaction to afford the desired products in excellent yields. the Partner Organisations 2014.
- Sagar,Vidyacharan, Shinde,Sharada, Duddu S.
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p. 37047 - 37050
(2014/11/08)
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- Rhodium-catalyzed intermolecular reaction of alkyl azides with diazo(aryl)acetates
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An efficient intermolecular interception of alkyl azides by diazo(aryl)acetates was achieved in the presence of dirhodium tetraoctanoate. The initial products were unstable α-imino esters, and overaddition of carbenoids to the C-N double bonds was avoided. After acidic workup, the corresponding α-keto esters were obtained in good to excellent yields. Georg Thieme Verlag Stuttgart New York.
- Gu, Peiming,Wu, Xiu-Ping,Su, Yan,Li, Xue-Qiang,Xue, Ping,Li, Rui
-
supporting information
p. 535 - 538
(2014/03/21)
-
- Enantio- and chemoselective Br?nsted-acid/Mg(nBu) 2 catalysed reduction of α-keto esters with catecholborane
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The first enantio- and chemoselective Br?nsted-acid catalysed reduction of α-keto esters with catecholborane has been developed. The α-hydroxy esters were obtained under mild reaction conditions in virtually quantitative yields and excellent enantioselectivities. With slight modifications both enantiomers can be obtained without any loss of selectivity. This journal is the Partner Organisations 2014.
- Enders, Dieter,St?ckel, Bianca A.,Rembiak, Andreas
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p. 4489 - 4491
(2014/04/17)
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- Highly chemo-, enantio-, and regioselective synthesis of α,α-disubstituted furanones by Cu-catalyzed conjugate addition
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A highly chemo-, enantio-, and regioselective synthesis of furanones bearing an α,α-disubstituted quaternary stereogenic center is reported. The Cu-catalyzed enantioselective conjugate addition of organoaluminum reagents to unsaturated ketoesters at room temperature and subsequent lactonization took place. Synthetic transformations of furanones represent facile approaches to various cyclic or acyclic compounds bearing a quaternary stereogenic center. Selective chemistry: A highly chemo-, enantio-, and regioselective synthesis of furanones bearing an α,α-disubstituted quaternary stereogenic center is reported (see scheme). Cu-catalyzed enantioselective conjugate addition of organoaluminum reagents to unsaturated ketoesters at room temperature and subsequent lactonization took place.
- Endo, Kohei,Yakeishi, Sayuri,Takayama, Ryotaro,Shibata, Takanori
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supporting information
p. 8893 - 8897
(2014/07/22)
-
- Dihaloiodoarenes: α,α-dihalogenation of phenylacetate derivatives
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A hypervalent iodine reagent-based α-carbonyl dihalogenation reaction is reported. Treating diazoacetate derivatives with either iodobenzene dichloride or iodotoluene difluoride results in gem-dichlorination or gem-difluorination products, respectively. The reaction is catalyzed by either Lewis acid or Lewis base activation of the aryl-λ3-iodane (ArIX2) species and proceeds rapidly and chemoselectively to the desired gem-difunctionalized products in good to excellent yield.
- Tao, Jason,Tran, Richard,Murphy, Graham K.
-
supporting information
p. 16312 - 16315
(2013/12/04)
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- Cu-catalyzed esterification reaction via aerobic oxygenation and C-C bond cleavage: An approach to α-ketoesters
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The Cu-catalyzed novel aerobic oxidative esterification reaction of 1,3-diones for the synthesis of α-ketoesters has been developed. This method combines C-C σ-bond cleavage, dioxygen activation and oxidative C-H bond functionalization, as well as provides a practical, neutral, and mild synthetic approach to α-ketoesters which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. A plausible radical process is proposed on the basis of mechanistic studies.
- Zhang, Chun,Feng, Peng,Jiao, Ning
-
supporting information
p. 15257 - 15262
(2013/11/06)
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- An efficient and practical synthesis of aryl and hetaryl α-keto esters
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A general and highly efficient method was developed for the synthesis of -keto esters by oxidative esterification of 2,2-dibromo-1-(het)arylethanones by sequential treatment with dimethyl sulfoxide and an alkanol. The versatility of the reaction was established by synthesizing a range of -keto esters by treatment of 2,2-dibromoethanones, derived from aryl or hetaryl ketones, with di-methyl sulfoxide and a cyclic or acyclic primary or secondary alcohol. The mechanism of the reaction was established by means of a detailed study. Georg Thieme Verlag Stuttgart · New York.
- Raghunadh, Akula,Meruva, Suresh Babu,Kumar, Nuka Anil,Kumar, Gudla Santosh,Rao, L. Vaikunta,Syamkumar
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p. 283 - 289
(2012/03/26)
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- Double nucleophilic N-alkylation of α-oxime-esters with Grignard reagents
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Double nucleophilic N-alkylation of α-oxime-esters, affording N,N-dialkyl-α-amino acids is herein described. Grignard reagents accomplished double N-alkylations via umpolung and various N,N-dialkylated α-amino acids were successfully synthesized in 15 min. Both electron-withdrawing sulfonyl groups and electron-donating silyl and methyl groups on oximes were available. Alkylmagnesium species and (E)-configuration of α-oxime-ester were essential to this cascade reaction.
- Mizutani, Yusuke,Tanimoto, Hiroki,Morimoto, Tsumoru,Nishiyama, Yasuhiro,Kakiuchi, Kiyomi
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supporting information
p. 5903 - 5906,4
(2020/08/20)
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- Asymmetric aerobic oxidation of α-hydroxy acid derivatives catalyzed by reusable, polystyrene-supported chiral N-salicylidene oxidovanadium tert-leucinates
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The direct immobilization of two different C-5-propargyl ether-modified, chiral N-salicylidene vanadyl(V) tert-leucinates onto 4-azidomethyl-substituted polystyrene by click chemistry was examined. Among the eight different solvents investigated, the resulting polystyrene-supported catalysts promote the asymmetric, aerobic oxidation of α-hydroxy (thio)esters and amides with enantioselectivities of up to 99% ee (selectivity factor up to 41) in chloroform. These polystyrene-supported catalysts can be readily recovered by filtration and reused for at least four consecutive runs without discernible loss of reactivity and enantioselectivity.
- Salunke, Santosh B.,Babu, N.Seshu,Chen, Chien-Tien
-
supporting information; experimental part
p. 1234 - 1240
(2011/06/26)
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- Polymer and silica supported tridentate schiff base vanadium catalysts for the asymmetric oxidation of ethyl mandelate - Activity, stability and recyclability
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Homogeneous tridentate Schiff base vanadium catalysts derived from salicylaldehydes and tert-leucinol or tert-leucine are known to be excellent catalysts for the asymmetric oxidation of α-hydroxy esters including ethyl mandelate. Herein, new analogous supported, semi-soluble and insoluble catalysts are synthesized and their activities relative to the homogeneous catalyst are reported. The new catalysts are characterized by 1H and 13C NMR spectroscopy, mass spectrometry (EI, ESI, FAB), X-ray crystallography, elemental analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, and nitrogen physisorption. The effects of support material, synthesis procedure, and reaction solvent are examined to probe the utility of these catalysts. Linear poly(styrene) supported catalysts are partially soluble under the reaction conditions, and it is shown that the soluble species contribute significantly to the catalytic reactivity. Insoluble catalysts based on the same vanadyl complexes supported on cross-linked poly(styrene) resin or mesoporous silica allow for catalyst recovery and recycle, showing equivalent selectivities over multiple reaction cycles. The mesoporous silica supported catalyst exhibits greater selectivity than the analogous homogeneous and polymer supported catalysts. Rigorous recycle studies show a loss of activity in each recycle, which is attributed to the decomposition of some portion of the vanadyl complexes in each cycle.
- Shiels, Rebecca A.,Venkatasubbaiah, Krishnan,Jones, Christopher W.
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experimental part
p. 2823 - 2834
(2009/11/30)
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- Organocatalytic asymmetric transferhydrogenation of β-nitroacrylates: Accessing β2-amino acids
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We describe a highly efficient and enantioselective Hantzsch ester mediated conjugate reduction of β-nitroacrylates that is catalyzed by a Jacobsen thiourea catalyst as a key step in a new route to optically active β2-amino acids. Copyright
- Martin, Nolwenn J. A.,Cheng, Xu,List, Benjamin
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supporting information; experimental part
p. 13862 - 13863
(2009/02/06)
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- Asymmetrie aerobic oxidation of α-hydroxy acid derivatives by C 4-symmetric, vanadate-centered, tetrakisvanadyl(V) clusters derived from N-salicylidene-α-aminocarboxylates
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(Chemical Equation Presented) A series of chiral vanadyl(V) methoxides bearing 3-t-butyl-5-substituted N-salicylene-L-valinate and L-t-leucinate as chiral auxiliaries has been prepared. In all cases except the 3,5-di-t-butyl analogue, they exist as monomers both in solution and in the single crystal state. In the case of the 3,5-di-t-butyl analogue, the architectural nature of the vanadyl(V) complex highly depends on the base used during the complex formation event. A pentanuclear C4-symmetric complex was formed when potassium salts were employed instead of the corresponding sodium salts. A central vanadate(V) unit serves to grip four identical chiral monomelic vanadyl(V) units together, by which a potassium ion sits on top of the four flanking units through carbonyl coordinations and serves to hold the whole cluster by cooperation with the central vanadate(V) unit. In comparison with the corresponding monomelic vanadyl(V) methoxide complex, the cluster complex was utilized to facilitate the asymmetric aerobic oxidations of various racemic α-hydroxyesters, -amides, and -thioesters with excellent selectivity factors (krel 40 to >500).
- Chen, Chien-Tien,Bettigeri, Sampada,Weng, Shiue-Shien,Pawar, Vijay D.,Lin, Ya-Hui,Liu, Cheng-Yuan,Lee, Way-Zen
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p. 8175 - 8185
(2008/02/13)
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- Surfactant-mediated solvent-free dealkylative cleavage of ethers and esters and trans-alkylation under neutral conditions
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A simple, surfactant-mediated, one-pot, solvent-free dealkylative cleavage of aryl ethers and esters followed by subsequent optional trans-alkylation under essentially neutral conditions has been developed.
- Bhattacharya, Apurba,Patel, Nitin C.,Vasques, Tomas,Tichkule, Ritesh,Parmar, Gaurang,Wu, Jiejun
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p. 565 - 567
(2007/10/03)
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- Facile synthesis of aryl α-keto esters via the reaction of aryl diazoacetate with H2O and DEAD
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A facile synthesis of aryl aα-keto esters in high yields is reported involving the reaction of aryl diazoacetate with H2O and diethyl azodicarboxylate (DEAD) catalyzed by dirhodium acetate. Georg Thieme Verlag Stuttgart.
- Guo, Zhenqiu,Huang, Haoxi,Fu, Qingquan,Hu, Wenhao
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p. 2486 - 2488
(2008/02/11)
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- Mechanism and scope of salen bifunctional catalysts in asymmetric aldehyde and α-ketoester alkylation
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Metal complexes of C2-symmetric Lewis acid/Lewis base salen ligands provide bifunctional activation resulting in rapid rates in the enantioselective addition of diethylzinc to aldehydes (up to 92% ee). Further experiments probed the reactivity of the individual Lewis acid and Lewis base components of the catalyst and established that both moieties are essential for asymmetric catalysis. These catalysts are also effective in the asymmetric addition of diethylzinc to α-ketoesters. This finding is significant because α-ketoesters alone serve as their own ligands to accelerate racemic 1,2-carbonyl addition of Et2Zn and racemic carbonyl reduction. The latter proceeds via a metalloene pathway, and often accounts for the predominant product. Singular Lewis acid catalysts do not accelerate enantioselective 1,2-addition over these two competing paths. The bifunctional amino salen catalysts, however, rapidly provide enantioenriched 1,2-addition products in excellent yield, complete chemoselectivity, and good enantioselectivity (up to 88% ee). A library of the bifunctional amino salens was synthesized and evaluated in this reaction. The utility of the α-ketoester method has been demonstrated in the synthesis of an opiate antagonist.
- Fennie, Michael W.,DiMauro, Erin F.,O'Brien, Erin M.,Annamalai, Venkatachalam,Kozlowski, Marisa C.
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p. 6249 - 6265
(2007/10/03)
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- Development of bifunctional salen catalysts: Rapid, chemoselective alkylations of α-ketoesters
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Lewis acid-Lewis base salen complexes have been identified as highly efficient catalysts for the addition of dialkylzincs to α-ketoesters. In contrast to aldehydes or ketones, the reaction between diethylzinc and α-ketoesters is significant in the absence of catalyst. In the presence of catalyst, the reaction rate is increased over 100-fold relative to the background. Furthermore, the reduction product, which is a major coproduct with other catalysts, is not observed with these bifunctional salens. As a result, high yields of the addition products can be obtained (57-99%). Both the Lewis acid and Lewis base portions of the catalyst are critical to the reactivity and selectivity. The two separate portions of the catalyst have been shown to function in a cooperative manner. Copyright
- DiMauro, Erin F.,Kozlowski, Marisa C.
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p. 12668 - 12669
(2007/10/03)
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- A general and simple synthesis of phenylglyoxylic esters via the oxidation of mandelic esters with ammonium chlorochromate adsorbed on alumina
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A general method for preparation of phenylglyoxylic esters by oxidation of mandelic esters with readily available ammonium chlorochromate adsorbed on alumina is described.
- Zhang, Gui-Sheng,Gong, Hui
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p. 3149 - 3153
(2007/10/03)
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- (Cyanomethylene)phosphoranes as Novel Carbonyl 1,1-Dipole Synthons: An Efficient Synthesis of α-Keto Acids, Esters, and Amides
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Carboxylic acids react with (cyanomethylene)triphenylphosphorane in the presence of EDCI to form cyano keto phosphoranes.The resulting ylides may then be oxidatively cleaved with ozone to form α,β-diketonitriles.These highly electrophilic products may then be converted in situ to α-keto acids, esters, and amides.
- Wasserman, Harry H.,Ho, Wen-Bin
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p. 4364 - 4366
(2007/10/02)
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- CHARACTERISTICS OF OXIDATIVE DECOMPOSITION OF tert-BUTYLPHENYL ACETATE
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The kinetics of accumulation has been studied for benzyl-α-hydroperoxyphenyl acetate, benzyl-α-hydroxyphenyl acetate, benzyl-α-oxophenyl acetate, benzaldehyde, benzylhydroperoxide (together with benzyl alcohol), perbenzoic, benzoic, and phenylacetic acids under conditions of initiated oxidation.The product composition indicates oxygen insertion in both α positions with similar rates.Products of intramolecular chain propagation are present in insignificant amount.
- Voronina, S. G.,Perkel', A. L.,Freidin, B. G.
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p. 1705 - 1710
(2007/10/02)
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- ELECTROCATALYTIC TRANSESTERIFICATION
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Transesterification took place electrocatalytically at mild conditions in cathodic compartment, on glassy carbon electrode, in acetonitrile solution of the mixture of ester and alcohol.
- Masumizu, Tatsuya,Nozawa, Koohei,Kawai, Ken-ichi,Nakajima, Shoichi
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- Reaction of Sydnones with Oxygen
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The reaction of 3-benzyl- and 3-(p-chlorobenzyl)-4-phenylsydnones (1a and 1b) and of 3-benzylsydnone (1c) with oxygen at room temperature in the dark is described.Possible rationalizations for the formation of the products obtained are suggested.
- Nakajima, Masayuki,Anselme, Jean-Pierre
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p. 1444 - 1448
(2007/10/02)
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- A MILD, RAPID, AND CONVENIENT ESTERIFICATION OF α-KETO ACIDS
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A new method for the esterification of α-keto acids with alkyl chloroformates is described, which is compatible with many functional groups.
- Domagala, John M.
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p. 4997 - 5000
(2007/10/02)
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