- 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)
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- 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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supporting information
p. 6709 - 6713
(2021/09/08)
-
- [Fe(bpy)3]2+-based porous organic polymers with boosted photocatalytic activity for recyclable organic transformations
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Three rigid metal porous organic polymers (POPs) based on an iron(ii) complex are prepared from the condensation reactions of an octahedral [Fe(bpy)3]2+-cored hexaaldehyde and three rod-like aromatic diamines. The POPs have been studied as the first series of earth-abundant metal complex-connected photocatalysts for heterogeneous visible light-driven oxidation of benzyl halides and enantioselective α-alkylation of aldehydes. Both yields and enantioselectivities of the reactions catalyzed by one of the POPs, which possesses the largest porosity, rival or even surpass those of the reactions homogeneously catalyzed by control [Fe(bpy)3]2+complexes. Moreover, POP catalysts are highly stable and exhibit a considerable activity after recycling 10 times.
- Liu, Hong-Kun,Lei, Yi-Fei,Tian, Peng-Ju,Wang, Hui,Zhao, Xin,Li, Zhan-Ting,Zhang, Dan-Wei
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supporting information
p. 6361 - 6367
(2021/03/22)
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- Metal-Free Oxidative Esterification of Ketones and Potassium Xanthates: Selective Synthesis of α-Ketoesters and Esters
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A novel and efficient oxidative esterification for the selective synthesis of α-ketoesters and esters has been developed under metal-free conditions. In the protocol, various α-ketoesters and esters are available in high yields from commercially available ketones and potassium xanthates. Mechanistic studies have proven that potassium xanthate not only promotes oxidative esterification but also provides an alkoxy moiety for the reaction, which involves the cleavage and reconstruction of C-O bonds.
- Luo, Xianglin,He, Runfa,Liu, Qiang,Gao, Yanping,Li, Jingqing,Chen, Xiuwen,Zhu, Zhongzhi,Huang, Yubing,Li, Yibiao
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p. 5220 - 5230
(2020/05/18)
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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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- ZnO nanoparticles: An efficient catalyst for transesterification reaction of α-keto carboxylic esters
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Pure ZnO nanoparticles were synthesized by a sustainable precipitation method using zinc nitrate and sodium hydroxide in aqueous medium at room temperature. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV–vis) spectroscopy and Brunauer-Emmett-Teller (BET) analysis. The XRD patterns indicate the formation of the hexagonal wurtzite phase with high purity and SEM-EDS analysis confirm the purity and a homogenous distribution of the nanostructures. The ZnO nanostructures present plate-like agglomerates, resulting in a quasi-spherical morphology. The catalytic activity of the formed ZnO nanoparticles was evaluated towards the transesterification reaction of different carboxylic esters in the presence of various alcohols. This catalyst is highly selective for the transesterification of α-keto carboxylic ester (methyl benzoylformate) and leads to ca. 97percent of product yield within 24 h of reaction time.
- Alegria, Elisabete C. B. A.,Karmakar, Anirban,Pombeiro, Armando J. L.,Rúbio, Guilherme M. D. M.,Ribeir, Ana P. C.,Saraiva, Marta S.,Soliman, Mohamed M. A.,da Silva, M. Fátima C. Guedes
-
-
- 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
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supporting information
p. 8438 - 8441
(2019/07/22)
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- Ambient and aerobic carbon-carbon bond cleavage toward α-ketoester synthesis by transition-metal-free photocatalysis
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The α-oxoesterification of the CC double bond in readily available enaminones enabling efficient synthesis of α-ketoesters is developed. The reactions showing general tolerance to the reactions of primary and secondary alcohols proceed well under air via Rose Bengal (RB)-based photocatalysis. Particularly, this mild synthetic method has been discovered to tolerate various polyhydroxylated substrates such as phenolic alcohol, diols and triols with an excellent selectivity of mono-oxoesterification. What is more noteworthy is that α-ketoester functionalized 16-dehydropregnenolone acetate resulting from the elaboration on a natural product has been obtained practically.
- Yu, Qing,Zhang, Yating,Wan, Jie-Ping
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supporting information
p. 3436 - 3441
(2019/06/24)
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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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- Organocatalytic Nitroaldol Reaction Associated with Deuterium-Labeling
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A deuterium-labeling reaction of nitroalkanes in deuterium oxide and the subsequent nitroaldol reaction have been accomplished under basic and organocatalytic conditions to provide the deuterium-labeled β-nitroalcohols in high yields and high deuterium contents. β-Deuterated β-nitroalcohols could be smoothly obtained from the reaction of nitroalkanes and various electrophiles using the easily-removal basic resin WA30. Furthermore, the asymmetric nitroaldol reaction using nitromethane and α-keto esters as electrophiles in the presence of a quinine-derived organocatalyst in deuterium oxide could provide the desired β-deuterated nitroalcohol derivatives with high enantioselectivities. (Figure presented.).
- Yamada, Tsuyoshi,Kuwata, Marina,Takakura, Ryoya,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
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supporting information
p. 637 - 641
(2017/12/13)
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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
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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
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supporting information
p. 1065 - 1070
(2018/05/01)
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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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- Catalytic asymmetric Meerwein-Ponndorf-Verley reduction of glyoxylates induced by a chiral N,N′-dioxide/Y(OTf)3 complex
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An asymmetric Meerwein-Ponndorf-Verley (MPV) reduction of glyoxylates was for the first time accomplished via an N,N′-dioxide/Y(OTf)3 complex with aluminium alkoxide and molecular sieves (MSs) as crucial additives. A variety of optically active α-hydroxyesters were obtained with excellent results. A possible reaction mechanism was proposed based on the experiments.
- Wu, Wangbin,Zou, Sijia,Lin, Lili,Ji, Jie,Zhang, Yuheng,Ma, Baiwei,Liu, Xiaohua,Feng, Xiaoming
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p. 3232 - 3235
(2017/03/20)
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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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- Copper(II)-Catalyzed Benzylic C(sp3)-H Aerobic Oxidation of (Hetero)Aryl Acetimidates: Synthesis of Aryl-α-ketoesters
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A straightforward method is developed in this paper for the synthesis of α-ketoesters through copper-catalyzed aerobic oxidation of (hetero)aryl acetimidates using molecular oxygen as a sustainable oxidant. The reaction represents the first example of the direct synthesis of aryl-α-ketoesters from arylacetimidates through the aerobic oxidation of a benzylic C(sp3)-H (CO) bond in moderate to good yield. This transformation occurs under mild reaction conditions with a wide range of substrates and utilizes a readily available oxidant and catalyst. The synthetic utility of this transformation is demonstrated through scaled-up synthesis. A plausible reaction mechanism is also proposed.
- Kumar, Yogesh,Jaiswal, Yogesh,Kumar, Amit
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p. 12247 - 12257
(2016/12/23)
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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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- 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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- 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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- 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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supporting information
p. 4489 - 4491
(2014/04/17)
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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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- Asymmetric friedel-crafts alkylation of α-substituted β-nitroacrylates: Access to β2,2-amino acids bearing indolic all-carbon quaternary stereocenters
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A highly enantioselective Friedel-Crafts alkylation reaction of indoles with acyclic α-substituted β-nitroacrylates is developed under the catalysis of Ni(ClO4)2-bisoxazoline complex at 1 mol % catalyst loading, affording chiral indolic β-nitroesters bearing all-carbon quaternary stereocenters in excellent yields and ees of up to 97%. Transformation of one of the products to β2,2-amino ester and tetrahydro-β-carboline through nitro reduction and sequential Pictet-Spengler cyclization was exemplified.
- Weng, Jian-Quan,Deng, Qiao-Man,Wu, Liang,Xu, Kai,Wu, Hao,Liu, Ren-Rong,Gao, Jian-Rong,Jia, Yi-Xia
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p. 776 - 779
(2014/03/21)
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- MICROCAPSULES CONTAINING A GAS-GENERATING PHOTOLABILE KETOACID OR KETOESTER AND USES THEREOF
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The present invention relates to water-dispersable microcapsules comprising an oil phase, e.g. a perfume, containing a photolabile α-ketoacid or α-ketoester capable of generating a gas upon exposure to light. The gas is able to cause an extension or the breaking of the microcapsule allowing the release of the oil phase and thus increasing the long-lastingness of the odor perception. The present invention concerns also the use of said microcapsules in perfumery as well as the perfuming compositions or perfumed articles comprising the invention's microcapsules to provide a prolonged release of fragrant molecules.
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Page/Page column 23
(2014/12/12)
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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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- 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.
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supporting information
p. 16312 - 16315
(2013/12/04)
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- Chiral-at-metal octahedral iridium catalyst for the asymmetric construction of an all-carbon quaternary stereocenter
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Metal-templated organocatalysis: The enantioselective formation of an all-carbon quaternary stereocenter is catalyzed by the ligand sphere of an inert bis-cyclometalated iridium complex (see picture). In this complex, the metal-centered chirality serves as the sole source for the effective asymmetric induction. Copyright
- Chen, Liang-An,Tang, Xiaojuan,Xi, Jianwei,Xu, Weici,Gong, Lei,Meggers, Eric
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supporting information
p. 14021 - 14025
(2014/01/06)
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- Highly homogeneous stereocontrolled construction of quaternary hydroxyesters by addition of dimethylzinc to α-ketoesters promoted by chiral perhydrobenzoxazines and B(OEt)3
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A highly efficient enantioselective addition of Me2Zn to α-ketoesters, assisted by a chiral perhydro-1,3-benzoxazine ligand, is described. This novel catalytic system offers homogeneous elevated enantioselectivities in the preparation of α-hydroxyesters that bear a quaternary stereocenter, with a minor dependence on electronic and steric effects when aromatic, heteroaromatic, or aliphatic α-ketoesters are employed. The catalyst can be recovered and reused without loss of activity.
- Infante, Rebeca,Nieto, Javier,Andres, Celia
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supporting information; experimental part
p. 4375 - 4379
(2012/05/20)
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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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- In situ generated "lanthanum(iii) nitrate alkoxide" as a highly active and nearly neutral transesterification catalyst
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In situ generated lanthanum(iii) nitrate alkoxide is a highly active and nearly neutral transesterification catalyst, which can promote non-epimerized transesterification of α-substituted chiral carboxylic esters under reflux conditions.
- Hatano, Manabu,Kamiya, Sho,Ishihara, Kazuaki
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supporting information
p. 9465 - 9467
(2012/10/29)
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- Readily available hydrogen bond catalysts for the asymmetric transfer hydrogenation of nitroolefins
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This paper focuses on readily accessible thiourea hydrogen bond catalysts derived from amino acids, whose steric and electronic features are modulated by their degree of substitution at the carbinol carbon center. These catalysts were applied in the asymmetric transfer hydrogenation of nitroolefins furnishing the chiral products in up to 99% yield and 86% enantiomeric excess. The proposed catalyst's mode of action is supported by mechanistic investigations.
- Schneider, Jakob F.,Lauber, Markus B.,Muhr, Vanessa,Kratzer, Domenic,Paradies, Jan
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supporting information; experimental part
p. 4323 - 4327
(2011/07/08)
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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
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p. 1234 - 1240
(2011/06/26)
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- Utilization of natural sunlight and air in the aerobic oxidation of benzyl halides
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Chemical equations presented. A novel, efficient oxidation of α-aryl halogen derivatives to the corresponding α-aryl carbonyl compounds at room temperature has been disclosed. Natural sunlight and air are successfully utilized in this approach through the combination of photocatalysis and organocatalysis. A plausible mechanism was proposed on the basis of the mechanistic studies.
- Su, Yijin,Zhang, Liangren,Jiao, Ning
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supporting information; experimental part
p. 2168 - 2171
(2011/06/21)
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- Chiral cobalt-catalyzed enantioselective aerobic oxidation of α-hydroxy esters
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A chiral cobalt-catalyzed enantioselective aerobic oxidative kinetic resolution of (±)-α-hydroxy esters, using molecular oxygen as a sole oxidant, is reported and a maximum of selectivity factor (s) 31.9 was achieved with >99% enantiomeric excess for unreacted α-hydroxy esters.
- Alamsetti, Santosh Kumar,Sekar, Govindasamy
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supporting information; experimental part
p. 7235 - 7237
(2010/12/24)
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- A rapid and green approach to chiral α-hydroxy esters: asymmetric transfer hydrogenation (ATH) of α-keto esters in water by use of surfactants
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A series of α-hydroxy esters were rapidly prepared (1.5 h) from α-keto esters via asymmetric transfer hydrogenation (ATH) in water by the use of surfactants for the first time. This green method, catalyzed by a water-soluble and recyclable Ru(II) complex, gave moderate to high enantioselectivities (up to 99.7% ee) with DTAB as an additive and HCOONa as the hydrogen source.
- Yin, Lu,Jia, Xian,Li, Xingshu,Chan, Albert S.C.
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experimental part
p. 2033 - 2037
(2010/01/16)
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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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- 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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- A remarkable effect of quaternary ammonium bromide for the N- hydroxyphthalimide-catalyzed aerobic oxidation of hydrocarbons
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A methodology for the aerobic oxidation of organic substrates in the absence of any metal catalyst has been established using combined catalytic system consisting of N-hydroxyphthalimide and quaternary ammonium bromide. Thus, various hydrocarbons were successfully oxidized under dioxygen atmosphere to the corresponding oxygenated compounds in good selectivities.
- Matsunaka, Katsuhisa,Iwahama, Takahiro,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 2165 - 2168
(2007/10/03)
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- Catalysis by Cobalt Schiff's Base Complexes in Highly Selective Conversion of Arylglyoxals to α-Aryl-α-hydroxyacetic Esters
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Cobalt Schiff's base complexes catalyse highly selective conversion of arylglyoxals to α-aryl-α-hydroxyacetic esters in alcohols; Lewis acidity of CoIII species may be responsible to the catalysis.
- Maruyama, K.,Murakami, Y.,Yoda, K.,Mashino, T.,Nishinaga, A.
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p. 1617 - 1618
(2007/10/02)
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- Mechanistic studies on palladium-catalyzed double carbonylation of aryl iodides affording α-Keto esters
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In relation to the mechanism of palladium-catalyzed carbonylation of aryl iodides to give α-keto esters, the carbonylation reactivity of some palladium complexes such as RPdIL2 (I: R = C6H5, L = P(C6H5/sub
- Yamashita,Sakakura,Kobayashi,Tanaka
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- Efficient acid fluoride synthesis via carbonylation of organic halides
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Palladium, platinum, cobalt, and rhodium triphenylphosphine complexes were found to catalyze the formation of acid fluorides via carbonylation of organic halides with fluoride salts.For palladium complex-catalyzed reactions, the use of cesium fluoride in polar solvents such as acetone and acetonitrile exhibited superior performance.The reaction took place even under an atmospheric pressure of carbon monoxide.The success of the acid fluoride synthesis is discussed in terms of the facility of oxidative addition of the starting material and the product.
- Sakakura, Toshiyasu,Chaisupakitsin, Malinee,Hayashi, Teruyuki,Tanaka, Masato
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p. 205 - 212
(2007/10/02)
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- Photochemistry of alkyl esters of benzoylformic acid
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The photodecomposition of several alkyl benzoylformates has been examined using quantum yield and laser flash photolysis techniques.The Norrish Type II reaction is a major triplet deactivation path in all substrates having γ-hydrogen atoms.Representative triplet lifetimes are 670, 500, and 310 ns, for the methyl, ethyl, and isopropyl esters, respectively, in 1:4 chlorobenzene:n-heptane at 298 K.Product studies suggest that several competing reactions are involved in the decay of the 1,4-biradical; some of these lead to highly absorbing (and presumably quenching) products, that make it essential to extrapolate quantum yields to "zero conversion" conditions.
- Encinas, M. V.,Lissi, E. A.,Zanocco, A.,Stewart, L. C.,Scaiano, J. C.
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p. 386 - 391
(2007/10/02)
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- SYNTHESIS AND REACTIONS OF PHENYLGLYOXAL ANILS
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Contrary to previous reports, the reaction of anilines and phenylglyoxal in toluene affords the expected anil PhCO-CH=N-Ar, 1.In many cases it is more convenient to carry out the reaction in methanol where the methanol adduct of 1 forms, which may be better isolated, characterised and stored.Since the alcohol adduct is in equilibrium with free 1, it can be used for synthetic purposes as precursor of 1 as in hydrolysis, Diels-Alder, and other reactions initiated by nucleophilic attack on the carbon-nitrogen double bond.
- Prato, Maurizio,Quintily, Ugo,Scorrano, Gianfranco
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p. 405 - 412
(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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- Photoinduced Alcoholysis of the Trichloroacetyl Group
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Irradiation of α,α,α-trichloroacetophenone (1a) in methanol afforded alcoholysis products methyl benzoate (2; X=H, R=Me) and methyl benzoylformate (3; X=H, R=Me) along with dichloroacetophenone.Formation of 2 was greatly favored in the presence of oxygen, whereas that of 3 was favored by the sensitization.Quenching studies showed that both alcoholysis products are derived from different excited triplet states.Reaction mechanisms involving the exciplex between 1 and oxygen are discussed.
- Izawa, Yasuji,Tomioka, Hideo,Natsume, Masashi,Beppu, Shinji,Tsujii, Hideo
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p. 4835 - 4838
(2007/10/02)
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