- Efficient Mukaiyama–Aldol Reaction with Aqueous Formaldehyde on a Hydrophobic Mesoporous Lewis Acid Polymer
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The design of robust water-compatible solid Lewis acid catalysts in the efficient utilization of aqueous formaldehyde is a challenging task. Herein, we describe an ytterbium triflate containing ordered mesoporous polymer (Yb(OTf)2-MP) that acts as a highly active and selective Lewis acid catalyst for the Mukaiyama–aldol reaction with aqueous formaldehyde. The unique capacity of hydrophobic surface and ordered mesoporosity was able to stabilize the hydrophilic and hydrophobic reactants simultaneously and catalyze the reaction selectively by minimizing water interference at active sites. Accordingly, it enabled a broad range of silyl enol ethers to be used to create structurally diverse β-hydroxy carbonyl molecules efficiently. Notably, the process can be scaled up easily to achieve the gram-scale production of the key intermediate of natural product sarkomycin. Additionally, it is stable under aqueous conditions and can be recovered easily and used repeatedly at least six times.
- Zhang, Fang,Liang, Chao,Wang, Zhen,Li, Hexing
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Read Online
- Palladium-Catalyzed Synthesis of α-Methyl Ketones from Allylic Alcohols and Methanol
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One-pot synthesis of α-methyl ketones starting from 1,3-diaryl propenols or 1-aryl propenols and methanol as a C1 source is demonstrated. This one-pot isomerization-methylation is catalyzed by commercially available Pd(OAc)2 with H2O as the only by-product. Mechanistic studies and deuterium labelling experiments indicate the involvement of isomerization of allyl alcohol followed by methylation through a hydrogen-borrowing pathway in these isomerization-methylation reactions.
- Biswal, Priyabrata,Samser, Shaikh,Meher, Sushanta Kumar,Chandrasekhar, Vadapalli,Venkatasubbaiah, Krishnan
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supporting information
p. 413 - 419
(2021/11/01)
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- Synthesis of a Bolm's 2,2′-Bipyridine Ligand Analogue and Its Applications
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A new method of synthesis of an analogue of Bolm's 2,2′-bipyridine ligand based on the catalytic [2+2+2] cyclotrimerization of 1-halodiynes with nitriles was developed. Crucial step of the whole synthesis turned out to be homodimerization of a substituted 2-bromopyridine to the corresponding bipyridine, that was studied and optimized. The newly prepared bipyridine (S,S)-2 was then tested as a chiral ligand in metal-catalyzed enantioselective reactions. Out of the studied reactions the most promising results were obtained in epoxide ring opening (82% yield, 98% ee) and Mukaiyama aldol reaction (>96% yield, 99/1 dr, 92% ee). In the case of Mukaiyama-aldol reaction as well as in the Michael addition, novel ligand 2 proved its robustness compared to Bolm's ligand as it was less sensitive to the purity of used reagents. (Figure presented.).
- Bedná?ová, Eva,Dra?ínsky, Martin,Malatinec, ?tefan,Císa?ová, Ivana,Lamaty, Frédéric,Kotora, Martin
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p. 2869 - 2878
(2018/08/17)
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- Dual Lewis Acid/Photoredox-Catalyzed Addition of Ketyl Radicals to Vinylogous Carbonates in the Synthesis of 2,6-Dioxabicyclo[3.3.0]octan-3-ones
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A combined Lewis acid/photoredox catalyst system enabled the intramolecular umpolung addition of ketyl radicals to vinylogous carbonates in the synthesis of 2,6-dioxabicyclo[3.3.0]octan-3-ones. This reaction proceeded on a variety of aromatic ketones to provide THF rings in good yield (up to 95%). Although diastereoselectivity was found to be modest (1.4-5:1) for the C-C bond forming reaction, the minor diastereomers were converted to 2,6-dioxabicyclo[3.3.0]octan-3-ones by an efficient Lewis acid-mediated epimerization cascade in up to 90% yield.
- Foy, Nicholas J.,Forbes, Katherine C.,Crooke, Anne Marie,Gruber, Maxwell D.,Cannon, Jeffrey S.
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p. 5727 - 5731
(2018/09/21)
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- Visible-Light-Mediated Rose Bengal-Catalyzed α-Hydroxymethylation of Ketones with Methanol
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A visible-light-mediated α-hydroxymethylation of ketones using methanol as the hydroxymethylating reagent has been developed. Using 1 mol% rose bengal as the photosensitizer and air as the green oxidant, the reactions proceeded smoothly at room temperature. Experimental studies indicate the reaction proceeded via a radical pathway. (Figure presented.).
- Yang, Jingya,Xie, Dongtai,Zhou, Hongyan,Chen, Shuwen,Duan, Jiaokui,Huo, Congde,Li, Zheng
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supporting information
p. 3471 - 3476
(2018/09/12)
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- Stereoselective Synthesis of Highly Substituted Tetrahydrofurans through Diverted Carbene O-H Insertion Reaction
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Copper- or rhodium-catalyzed reactions of diazocarbonyl compounds with β-hydroxyketones give highly substituted tetrahydrofurans with excellent diastereoselectivity. Under mild conditions, the single-step process starts as a carbene O-H insertion reaction, but is diverted by an intramolecular aldol reaction. Gone astray: Copper- or rhodium-catalyzed reactions of diazocarbonyl compounds with β-hydroxyketones give highly substituted tetrahydrofurans with excellent diastereoselectivity. The single-step reaction proceeds under mild conditions, starting as a carbene O-H insertion reaction, but then diverting to an intramolecular aldol reaction.
- Nicolle, Simon M.,Lewis, William,Hayes, Christopher J.,Moody, Christopher J.
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supporting information
p. 8485 - 8489
(2015/11/27)
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- Toward chemistry-based design of the simplest metalloenzyme-like catalyst that works efficiently in water
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Enzymes exhibit overwhelmingly superior catalysis compared with artificial catalysts. Current strategies to rival enzymatic catalysis require unmodified or minimally modified structures of active sites, gigantic molecular weight, and sometimes the use of harsh conditions such as extremely low temperatures in organic solvents. Herein, we describe a design of small molecules that act as the simplest metalloenzyme-like catalysts that can function in water, without mimicking enzyme structures. These artificial catalysts efficiently promoted enantioselective directtype aldol reactions using aqueous formaldehyde. The reactions followed Michaelis-Menten kinetics, and heat-resistant asymmetric environments were constructed in water.
- Kitanosono, Taku,Kobayashi, Shu
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supporting information
p. 133 - 138
(2015/02/19)
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- Highly active, water-compatible and easily separable magnetic mesoporous Lewis acid catalyst for the Mukaiyama-Aldol reaction in water
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A novel magnetic mesoporous Lewis acid catalyst was prepared through immobilizing Yb(OTf)3 on a sodium propylsulphonate and phenyl group co-functionalized magnetic core-mesoporous silica shell composite. The obtained Yb(OTf)2-SO3Na&Ph-MCMSS catalyst had a typical core-shell structure with a Fe3O4 magnetic core, a middle amorphous silica layer and a multifunctional mesoporous silica shell with radial pore channels. In water medium Mukaiyama-Aldol reactions, it exhibited a higher catalytic reactivity than that of the homogeneous catalyst Yb(OTf)3, and control catalysts Yb(OTf)2-SO3Na-MCMSS without phenyl groups inside the mesoporous channels, Yb(OTf)2-SO 3Na&Ph-MCSS without a mesoporous structure, mesoporous Yb(OTf)2-SO3Na&Ph-MCM-41 with an irregular morphology and nonporous Yb(OTf)2-SO3Na-Amberlyst-15 ion-exchange resin. The systematic analysis demonstrated that this excellent catalytic performance could be attributed to the synergetic effect resulting from its radial mesoporous channels and the pore surface hydrophobicity, leading to the increased accessibility of actives sites and the decreased diffusion limitation of reactants. More importantly, this catalyst was stable in water and could be easily separated with a simple magnet and reused at least six times without loss of catalytic activity. This journal is the Partner Organisations 2014.
- Zhang, Fang,Wu, Xiaotao,Liang, Chao,Li, Xiaoyan,Wang, Zhen,Li, Hexing
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p. 3768 - 3777
(2014/08/05)
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- Iron- and bismuth-catalyzed asymmetric mukaiyama aldol reactions in aqueous media
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We have developed asymmetric Mukaiyama aldol reactions of silicon enolates with aldehydes catalyzed by chiral FeII and BiIII complexes. Although previous reactions often required relatively harsh conditions, such as strictly anhydrous conditions, very low temperatures (-78 °C), etc., the reactions reported herein proceeded in the presence of water at 0 °C. To find appropriate chiral water-compatible Lewis acids for the Mukaiyama aldol reaction, many Lewis acids were screened in combination with chiral bipyridine L1, which had previously been found to be a suitable chiral ligand in aqueous media. Three types of chiral catalysts that consisted of a FeII or BiIII metal salt, a chiral ligand (L1), and an additive have been discovered and a wide variety of substrates (silicon enolates and aldehydes) reacted to afford the desired aldol products in high yields with high diastereo- and enantioselectivities through an appropriate selection of one of the three catalytic systems. Mechanistic studies elucidated the coordination environments around the FeII and BiIII centers and the effect of additives on the chiral catalysis. Notably, both Bronsted acids and bases worked as efficient additives in the Fe II-catalyzed reactions. The assumed catalytic cycle and transition states indicated important roles of water in these efficient asymmetric Mukaiyama aldol reactions in aqueous media with the broadly applicable and versatile catalytic systems. Copyright
- Kitanosono, Taku,Ollevier, Thierry,Kobayashi, Shu
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supporting information
p. 3051 - 3062
(2014/01/06)
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- An extremely stable and highly active periodic mesoporous Lewis acid catalyst in water-medium Mukaiyama-aldol reaction
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A periodic mesoporous Lewis acid catalyst ((OTf)2Sc-SO 3-Ph-PMO) was synthesized through chelating scandium triflate (Sc(OTf)3) with sodium benzenesulfonate-functionalized periodic mesoporous silica (PhSO3Na-Ph-PMO). Compared with homogeneous catalyst Sc(OTf)3 and mesoporous SBA-15-supported scandium triflate catalyst ((OTf)2Sc-SO3-Ph-SBA-15), it exhibited superior catalytic activity and selectivity in water-medium Mukaiyama-aldol reaction. Hydrophobicity tests and substrate adsorption experiments demonstrated that its unique catalytic performance was related to the combined advantage of mesoporosity and hydrophobic microenvironment, which effectively stabilized and concentrated the substances as well as decreased intrinsic mass transfer resistance. Noted that the periodically arranged Lewis acids in the mesoporous silica framework inhibited the active sites leaching, leading to its high catalytic recyclability with almost unchanged catalytic efficiency for more than 10 times in water media.
- Zhang, Fang,Liang, Chao,Chen, Mingzheng,Guo, Haibing,Jiang, Huangyong,Li, Hexing
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supporting information
p. 2865 - 2871
(2013/10/08)
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- Enantioselective evans-tishchenko reduction of β-hydroxyketone catalyzed by lithium binaphtholate
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Lithium diphenylbinaphtholate catalyzed the enantioselective Evans-Tishchenko reduction of achiral β-hydroxyketones to afford monoacyl-protected 1,3-diols with high stereoselectivities. In the reaction of racemic β-hydroxyketones, kinetic optical resolution occurred in a highly stereoselective manner.
- Ichibakase, Tomonori,Nakatsu, Masato,Nakajima, Makoto
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experimental part
p. 5008 - 5019
(2011/08/10)
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- Rhodium-catalyzed asymmetric formal olefination or cycloaddition: 1,3-dicarbonyl compounds reacting with 1,6-diynes or 1,6-enynes
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A cationic rhodium(I) complex catalyzes the title reaction of 1,6-diynes through a [2+2+2] cycloaddition and subsequent electrocyclic ring opening (see scheme; cod=1,5-cyclooctadiene, H8-binap=2,2′- bis(diphenylphosphino)-5,5′,6,6′,7,7′,8,8′-octahydro-1, 1′-binaphthyl). The asymmetric intramolecular [2+2+2] cycloaddition of 1,3-dicarbonyl compounds with 1,6-enynes was also accomplished. Copyright
- Suda, Takeshi,Noguchi, Keiichi,Tanaka, Ken
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p. 4475 - 4479
(2011/06/25)
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- Chiral scandium-catalyzed enantioselective hydroxymethylation of ketones in water
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Scandium-catalyzed enantioselective hydroxymethylation of ketones has been developed using aqueous formaldehyde (formalin) in water. The addition of a catalytic amount of pyridine enables the use of ketones directly in asymmetric hydroxymethylation reactions. (Chemical equation presented).
- Kobayashi, Shu,Kokubo, Masaya,Kawasumi, Katsuaki,Nagano, Takashi
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experimental part
p. 490 - 492
(2010/09/03)
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- Purification and characterization of a (r)-1-phenyl-1, 3-propanediol- producing enzyme from trichosporon fermentans aj-5152 and enzymatic (r)-1-phenyl-1, 3-propanediol production
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An (R)-1-phenyl-1, 3-propanediol-producing enzyme was purified from Trichosporon fermentans AJ-5152. It was NADPH-dependent and converted 3-hydroxy-1- phenylpropane-1-one (HPPO) to (R)-1-phenyl-1, 3-propanediol [(R)-PPD] with anti-Prelog's specificity. It
- Kira, Ikuo,Onishi, Norimasa
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experimental part
p. 1640 - 1646
(2010/03/24)
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- Lewis acid catalysis in water with a hydrophilic substrate: Scandium-catalyzed hydroxymethylation with aqueous formaldehyde in water
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(Chemical Equation Presented) Synthesis in deep water: For the title reaction, which proceeds with high selectivities, acid-base interactions between the Sc catalyst and HCHO are important. The reaction was used in the synthesis of an odorant to demonstra
- Kokubo, Masaya,Ogawa, Chikako,Kobayashi, Shu
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supporting information; experimental part
p. 6909 - 6911
(2009/04/06)
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- Scandium(Iii) fluoride as a novel catalyst for hydroxymethylation of dimethylsilyl enolates in aqueous media
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Hydroxymethylation of dimethylsilyl (DMS) enolates using aqueous formaldehyde solution is catalyzed by scandium(III) fluoride (ScF3) in aqueous media to give the corresponding β-hy-droxy ketones in good to excellent yields. Whilst the DMS enola
- Kokubo, Masaya,Kobayashi, Shu
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scheme or table
p. 1562 - 1564
(2009/04/07)
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- Synthesis of an immunomodulator (+)-conagenin and its analogs
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Stereoselective synthesis of an immunomodulator (+)-conagenin was achieved. Both amine and carboxylic acid moieties were prepared from commercially available optically active methyl 3-hydroxy-2-methylpropanoate using dirhodium(II)-catalyzed C-H amination
- Yakura, Takayuki,Yoshimoto, Yuya,Ishida, Chisaki,Mabuchi, Shunsuke
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p. 4429 - 4438
(2008/02/02)
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- PROCESS FOR PRODUCTION OF OPTICALLY ACTIVE HYDROXYMETHYLATED COMPOUNDS AND CATALYST THEREFOR
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[PROBLEMS] To provide a process for producing optically active hydroxymethylated compounds in high yields at high stereoselectivity with broad substrate generality, and a catalyst for the production. [MEANS FOR SOLVING PROBLEMS] The process comprises reac
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Page/Page column 11-12
(2008/06/13)
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- A heterogeneous silica-supported scandium/ionic liquid catalyst system for organic reactions in water
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(Figure Presented) Several carbon-carbon bond-forming reactions are catalyzed by a silica-supported scandium triflate catalyst combined with an ionic liquid. The combination of these two components creates a hydrophobic reaction environment in water (see scheme; blue: water, yellow: substrate, orange: ionic liquid).
- Gu, Yanlong,Ogawa, Chikako,Kobayashi, Juta,Mori, Yuichiro,Kobayashi, Shu
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p. 7217 - 7220
(2007/10/03)
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- Zn(pybox)-complex-catalyzed asymmetric aqueous Mukaiyama-Aldol reactions
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Catalytic asymmetric aldol reactions in aqueous media have been developed using chiral zinc complex. The aldol products have been obtained in high yields, high diastereocontrol, and good level of enantioselectivity. Various aromatic and α,β-unsaturated al
- Jankowska, Joanna,Mlynarski, Jacek
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p. 1317 - 1321
(2007/10/03)
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- Bismuth triflate-chiral bipyridine complexes as water-compatible chiral lewis acids
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(Chemical Equation Presented) Catalytic asymmetric hydroxymethylation of silicon enolates with an aqueous formaldehyde solution has been developed using a chiral bismuth complex. This is the first example of highly enantioselective reactions using a chira
- Kobayashi, Shu,Ogino, Tsuyoshi,Shimizu, Haruka,Ishikawa, Shunpei,Hamada, Tomoaki,Manabe, Kei
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p. 4729 - 4731
(2007/10/03)
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- Polymer-micelle incarcerated scandium as a polymer-supported catalyst for high-throughput organic synthesis
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A novel immobilization technique for Sc(OTf)3, a polymer-micelle incarcerated (PMI) method, has been developed. PMI Sc(OTf)3 is highly active in several fundamental carbon-carbon bond-forming reactions. The catalyst is recovered quan
- Takeuchi, Masahiro,Akiyama, Ryo,Kobayashi, Shu
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p. 13096 - 13097
(2007/10/03)
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- Catalytic asymmetric hydroxymethylation of silicon enolates using an aqueous solution of formaldehyde with a chiral scandium complex
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Catalytic asymmetric hydroxymethylation of silicon enolates has been achieved. In this reaction, an aqueous solution of formaldehyde can be used to realize an easy and safe procedure, and high enantioselectivities have been obtained. This is the first exa
- Ishikawa, Shunpei,Hamada, Tomoaki,Manabe, Kei,Kobayashi, Shu
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p. 12236 - 12237
(2007/10/03)
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- Lewis acid-catalyzed asymmetric hydroxymethylation of silicon enolates in aqueous media
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Asymmetric hydroxymethylation of silicon enolates with formaldehyde in aqueous media has been achieved using praseodymium triflate and a chiral crown ether. Formaldehyde aqueous solution can be directly used for the reactions, and a water/THF mixture was found to be the best solvent system. This is the first example of catalytic asymmetric hydroxymethylation of silicon enolates.
- Manabe, Kei,Ishikawa, Shunpei,Hamada, Tomoaki,Kobayashi, Shu
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p. 10439 - 10444
(2007/10/03)
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- Aldol Synthesis with an Aqueous Solution of Formalin
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With an aqueous solution of formalin, aldol reaction of trimethylsilyl enol ether proceeds moderately using tetrabutylammonium fluoride (TBAF). Furthermore, catalytic asymmetric hydroxymethylation with trimethoxysilyl enol ether using water tolerant (R)-B
- Ozasa, Nobuko,Wadamoto, Manabu,Ishihara, Kazuaki,Yamamoto, Hisashi
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p. 2219 - 2221
(2007/10/03)
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- Lewis base-promoted aldol reaction of dimethylsilyl enolates in aqueous dimethylformamide: Use of calcium chloride as a Lewis base catalyst
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In the presence of CaCl2, dimethylsilyl (DMS) enolates smoothly reacted with aldehydes under mild conditions to give aldol adducts in good to high yields. The catalytic activities of various metal and tetrabutylammonium salts have revealed that CaCl2 works as a Lewis base catalyst to activate DMS enolates. The CaCl2-promoted reaction proceeded even in the presence of water or in pure water. This catalytic system was applicable to the aldol reaction with aqueous aldehydes such as formalin. Copyright
- Miura, Katsukiyo,Nakagawa, Takahiro,Hosomi, Akira
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p. 536 - 537
(2007/10/03)
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- Highly diastereoselective aldol synthesis from α-iodo ketones in aqueous media
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Highly diastereoselective aldol synthesis from α-iodo ketones was promoted under aqueous conditions by a distannane system, (n-Bu3Sn)2, n-Bu2SnF2 and HMPA. Aqueous solutions of acetaldehyde, formaldehyde and piv
- Shibata, Ikuya,Kawasaki, Masatsugu,Yasuda, Makoto,Baba, Akio
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p. 689 - 690
(2007/10/03)
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- Reductive intramolecular cyclization of α-bromo silyl ethers mediated by samarium diiodide
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A new SmI2-promoted intramolecular reductive cyclization of β-(α-bromo siloxy) carbonyl compounds is reported.
- Park,Lee,Kwon,Kim
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p. 2745 - 2746
(2007/10/03)
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- Lewis acid catalysis in micellar systems. Sc(OTf)3-catalyzed aqueous aldol reactions of silyl enol ethers with aldehydes in the presence of a surfactant
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Scandium triflate (Sc(OTf)3)-catalyzed aldol reactions of silyl enol ethers with aldehydes were successfully carried out in micellar systems. While the reactions proceeded sluggishly in water, remarkable enhancement of the reactivity was observ
- Kobayashi, Shu,Wakabayashi, Takeshi,Nagayama, Satoshi,Oyamada, Hidekazu
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p. 4559 - 4562
(2007/10/03)
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- Lewis acid catalysis in aqueous media: Copper(II)-catalyzed aldol and allylation reactions in a water-ethanol-toluene solution
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Cu(OTf)2 was found to be a stable Lewis acid in aqueous media and to activate carbonyl compounds effectively. Aldol reactions of silyl enol ethers with aldehydes and allylation reactions of tetraallyltin with carbonyl compounds proceeded smooth
- Kobayashi, Shu,Nagayama, Satoshi,Busujima, Tsuyoshi
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p. 959 - 960
(2007/10/03)
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- Rare Earth Metal Complexes as Water-Tolerant Lewis Acid Catalysts in Organic Synthesis
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Rare earth metal triflates are stable in aqueous media and can act as Lewis acid catalysts in several carbon-carbon bond forming reactions. This article describes some of these reactions; aldol and Mannich-type reactions in aqueous solution, and Friedel-Crafts acylations and Fries rearrangement in organic solvents. The reactions proceeded smoothly in the presence of a catalytic amount of the triflate under mild conditions. Moreover, the catalysts could be recovered after the reactions were completed and could be reused.
- Kobayashi,Hashiya,Ishitani,Moriwaki,Nagayama
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p. 193 - 202
(2007/10/03)
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- Tris(pentafluorophenyl)boron as an Efficient, Air Stable, and Water Tolerant Lewis Acid Catalyst
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Tris(pentafluorophenyl)boron is an efficient, air stable, and water tolerant Lewis acid catalyst for the aldol-type and Michael reactions of silyl enol ethers with carbonyl compounds or other electrophiles (trimethyl orthoformate, dimethal acetal, and chloromethyl methyl ether), the allylation reaction of allylsilanes with aldehydes, and the Diels-Alder reaction of dienes with α,β-unsaturated-aldehydes.A solution of formaldehyde in water is applicable as an electrophile.Also, the aldol-type reaction of ketene silyl acetals with aromatic or aliphatic imines is successfully carried out using the same catalyst.
- Ishihara, Kazuaki,Hanaki, Naoyuki,Funahashi, Miyuki,Miyata, Mayumi,Yamamoto, Hisashi
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p. 1721 - 1730
(2007/10/02)
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- Lanthanide Triflates as Water-Tolerant Lewis Acids. Activation of Commercial Formaldehyde Solution and Use in the Aldol Reaction of Silyl Enol Ethers with Aldehydes in Aqueous Media
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Lanthanide trifluoromethanesulfonates (triflates), especially ytterbium triflate (Yb(OTf)3), were found to be stable Lewis acids in water.In the presence of a catalytic amount of lanthanide triflate, formaldehyde in water solution (commercial formaldehyde
- Kobayashi, Shu,Hachiya, Iwao
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p. 3590 - 3596
(2007/10/02)
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- Repeated Use of the Catalyst in Ln(OTf)3-Catalyzed Aldol and Allylation Reactions
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The lanthanoide trifluoromethanesulfonate (lanthanoid triflate)-catalyzed aldol reactions of silyl enol ethers with aldehydes and allylation reactions of tetraallyltin with aldehydes proceeded smoothly in a water-ethanol-toluene system.The reactions proce
- Kobayashi, Shu,Hachiya, Iwao,Yamanoi, Yoshinori
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p. 2342 - 2344
(2007/10/02)
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- Process for producing a beta-ketoalcohol
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Herein is disclosed a process for producing a β-ketoalcohol by the oxidative ring-opening reaction of a 1,3-dioxane derivative, said β-ketoalcohol being able to be a substrate for asymmetric reaction.
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- Lanthanide Trifluoromethanesulfonates as Stable Lewis Acids in Aqueous Media. Yb(OTf)3 Catalyzed Hydroxymethylation Reaction of Silyl Enol Ethers with Commercial Formaldehyde Solution
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Silyl enol ethers smoothly react with commercial formaldehyde solution to give the corresponding hydroxymethylated adducts in high yields by the promotion of a catalytic amount of ytterbium(III) triflate (Yb(OTf)3), which is a stable Lewis acid in aqueous
- Kobayashi, Shu
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p. 2187 - 2190
(2007/10/02)
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- Metal-carbonyl-induced Reaction of 2-Isoxazolines. Ring Cleavage and Reduction by Pentacarbonyliron or Nonacarbonyldi-iron
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3,5-Disubstituted 2-isoxazolines (1a-f) undergo N-O and C-4 - C-5 bond-cleavage reaction with pentacarbonyliron and photoirradiation in methanol to give two fragments (aldehydes and ketones).The ketones could be derived from reduction of the complexed 1-substituted vinylnitrene intermediate and subsequent hydrolysis.Substituent effects have a significant influence on the course of the reaction. 2-Isoxazolines (1h and i) having no substituent at C-5 undergo N-O bond cleavage to give β-hydroxy- and β-methoxy-ketones, in addition to the above mentioned cleavage of the N-O and C-4 - C-5 bonds.Furthermore, 2-isoxazolines (1j and k) bearing a substituent such as an acetoxy or ethoxy group at C-5 undergo N-O bond cleavage, and concomitant elimination of the substituent acetoxy or ethoxy group, leading to β-aminoenones.However, in the case of 2-isoxazolines (1l and m) bearing a piperidin-1-yl group at C-5, the N-O and C-4 - C-5 bond-cleavage reactions predominate over the elimination of the C-5-substituent.Mechanisms are also proposed for the formation of the β-substituted ketones.Similar reactions were also effected thermally for several 2-isoxazolines with nonacarbonyldi-iron.
- Nitta, Makoto,Kobayashi, Tomoshige
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p. 2103 - 2108
(2007/10/02)
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- Stereoselective Reduction of α-Methyl-β-hydroxy Ketones with Zinc Borohydride
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Zinc borohydride reduction of α-methyl-β-hydroxy ketones 3 produced the erythro-2-methyl-1,3-glycol derivatives 4 with high stereoselectivity.The selectivity was particularly high when an olefinic group was conjugated to the carbonyl group.Reduction of th
- Nakata, Tadashi,Tani, Yoichiro,Hatozaki, Masayoshi,Oishi, Takeshi
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p. 1411 - 1415
(2007/10/02)
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- RING CLEVEAGE REACTIONS OF SUBSTITUTED 2-ISOXAZOLINES BY PENTACARBONYLIRON UNDER ULTRAVIOLET IRRADIATION
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The photoirradiation of 3,5-disubstituted 2-isoxazolines and Fe(CO)5 in MeOH causes the N-O and C4-C5 bond cleveage to give two fragments of aldehydes and ketones, while that of 2-isoxazolines having no substituent at 5-position gives additional β-hydroxy- and β-methoxyketones.
- Nitta, Makoto,Kobayashi, Tomoshige
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