- Siloxy Esters as Traceless Activators of Carboxylic Acids: Boron-Catalyzed Chemoselective Asymmetric Aldol Reaction**
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The catalytic asymmetric aldol reaction is among the most useful reactions in organic synthesis. Despite the existence of many prominent reports, however, the late-stage, chemoselective, catalytic, asymmetric aldol reaction of multifunctional substrates is still difficult to achieve. Herein, we identified that in situ pre-conversion of carboxylic acids to siloxy esters facilitated the boron-catalyzed direct aldol reaction, leading to the development of carboxylic acid-selective, catalytic, asymmetric aldol reaction applicable to multifunctional substrates. Combining experimental and computational studies rationalized the reaction mechanism and led to the proposal of Si/B enediolates as the active species. The silyl ester formation facilitated both enolization and catalyst turnover by acidifying the α-proton of substrates and attenuating poisonous Lewis bases to the boron catalyst.
- Fujita, Taiki,Kanai, Motomu,Mitsunuma, Harunobu,Sameera, W. M. C.,Yamane, Mina
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supporting information
p. 24598 - 24604
(2021/10/14)
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- Chain propagation determines the chemo- And regioselectivity of alkyl radical additions to C-O: Vs. C-C double bonds
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Investigations into the selectivity of intermolecular alkyl radical additions to C-O- vs. C-C-double bonds in α,β-unsaturated carbonyl compounds are described. Therefore, a photoredox-initiated radical chain reaction is explored, where the activation of the carbonyl-group through an in situ generated Lewis acid-originating from the substrate-enables the formation of either C-O or the C-C-addition products. α,β-Unsaturated aldehydes form selectively 1,2-, while esters and ketones form the corresponding 1,4-addition products exclusively. Computational studies lead to reason that this chemo- and regioselectivity is determined by the consecutive step, i.e. an electron transfer, after reversible radical addition, which eventually propagates the radical chain.
- Paulisch, Tiffany O.,Strieth-Kalthoff, Felix,Henkel, Christian,Pitzer, Lena,Guldi, Dirk M.,Glorius, Frank
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p. 731 - 736
(2020/02/03)
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- Copper-catalyzed diastereoselective synthesis of β-boryl-α-quaternary carbon carboxylic esters
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Cu(i)-Catalyzed diastereoselective carboboration of α-alkyl-substituted α,β-unsaturated carboxylic esters to produce β-boryl-α-quaternary carbon esters was developed. The carbon skeletons of dialkyl sulfates, primary allyl halides, and benzyl bromides were transferred to the α-position of the substrates to provide products in moderate to good yields with a diastereoselectivity of >95% in most cases. Substrates bearing a β-(hetero)aryl substituent gave higher diastereoselectivities than those bearing a linear β-alkyl substituent. The crystal structure of the potassium trifluoroborate derivative shows that the reactions probably go through a copper(i) enolate intermediate and the diastereoselectivity arises from the electrophilic attack of electrophiles to the less hindered side of the enolates.
- Zuo, Ya-Jie,Zhong, Zhuoran,Fan, Yinkun,Li, Xiangyu,Chen, Xiaolu,Chang, Yuwei,Song, Ruihu,Fu, Xinpeng,Zhang, Anling,Zhong, Chong-Min
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supporting information
p. 9237 - 9242
(2019/01/03)
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- Strong Lewis acid air-stable cationic titanocene perfluoroalkyl(aryl) sulfonate complexes as highly efficient and recyclable catalysts for C-C bond forming reactions
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A series of strong Lewis acid air-stable titanocene perfluoroalkyl(aryl) sulfonate complexes Cp2Ti(OH2)2(OSO 2X)2·THF (X = C8F17, 1·THF; X = C4F9, 2·H2O· THF; X = C6F5, 3) were successfully synthesized by the treatment of Cp2TiCl2 with C8F 17SO3Ag, C4F9SO3Ag and C6F5SO3Ag, respectively. In contrast to well-known titanocene bis(triflate), these complexes showed no change in open air over three months. TG-DSC analysis showed that 1·THF, 2·H 2O·THF and 3 were thermally stable at 230 °C, 220°C and 280°C, respectively. Conductivity measurements showed that these complexes underwent ionic dissociation in CH3CN solution. X-ray analysis results confirmed that 2·H2O·THF and 3 were cationic. ESR spectra showed that the Lewis acidity of 1·THF (1.06 eV) was higher than that of Sc3+ (1.00 eV) and Y3+ (0.85 eV). UV/Vis spectra showed a significant red shift due to the strong complex formation between 10-methylacridone and 2·H2O·THF. Fluorescence spectra showed that the Lewis acidity of 2 (λem = 477 nm) was higher than that of Sc3+ (λem = 474 nm). These complexes showed high catalytic ability in various carbon-carbon bond forming reactions. Moreover, they show good reusability. Compared with 1·THF, 2·H2O·THF and 3 exhibit higher solubility and better catalytic activity, and will find broad applications in organic synthesis. This journal is the Partner Organisations 2014.
- Li, Ningbo,Wang, Jinying,Zhang, Xiaohong,Qiu, Renhua,Wang, Xie,Chen, Jinyang,Yin, Shuang-Feng,Xu, Xinhua
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supporting information
p. 11696 - 11708
(2014/07/22)
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- Mukaiyama aldol reactions catalyzed by a trimeric organo aluminum(III) alkoxide
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Mukaiyama aldol reactions of enol ethers with a variety of aldehydes and ketones are efficiently catalyzed at 0-25 °C by the sterically bulky trimeric organo aluminum(III) alkoxide 1 synthesized via the reaction of 3 equiv of AlMe3 with tripodal tris(2-hydroxy-3-tert-butyl-5-methylphenyl) methane and the elimination of 3 equiv of methane. Comparisons of its catalytic properties with the less sterically hindered analogue 2, the more sterically hindered analogue 3, a monomeric aluminum near-analogue 4, and a dimeric alumatrane 5 revealed that 1 possesses superior activity.
- Kim, So Han,Yoon, Sungwoo,Kim, Youngjo,Verkade, John G.
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p. 1193 - 1206
(2014/09/30)
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- Synthesis and structures of air-stable binuclear hafnocene perfluorobutanesulfonate and perfluorobenzenesulfonate and their catalytic application in C-C bond-forming reactions
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The two air-stable m2-hydroxy-bridged binuclear hafnocene perfluorobutanesulfonate and perfluorobenzenesulfonate complexes were successfully synthesized. The high catalytic activity and recyclability of these complexes were exemplified for various carbon-carbon bond formation reactions. Compared with our previously reported hafnocene perfluorooctanesulfonate, these complexes show stronger Lewis acidity and better catalytic activity, and should find broad applications in organic synthesis.
- Li, Ningbo,Zhang, Xiaohong,Xu, Xinhua,Chen, Yun,Qiu, Renhua,Chen, Jinyang,Wang, Xie,Yin, Shuang-Feng
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supporting information
p. 2430 - 2440
(2013/10/01)
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- Mukaiyama aldol reaction of trimethylsilyl enolate with aldehyde catalyzed by CuI
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Cuprous iodide has been found to be a very effective catalyst for Mukaiyama aldol reaction of trimethylsilyl ketene acetal with aldehydes. The new catalytic system promotes efficiently the Mukaiyama aldol reaction in DMF to produce corresponding β-hydroxy carbonyl compounds in high yield.
- Kalita, Hima Rani,Borah, Arun Jyoti,Phukan, Prodeep
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p. 289 - 292
(2013/05/22)
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- Gallium(III) triflate catalyzed diastereoselective mukaiyama aldol reaction by using low catalyst loadings
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A mild method for the diastereoselective Mukaiyama aldol reaction is reported. By using a low loading of the gallium(III) triflate catalyst (down to 0.01 mol-%), the transformation proceeds efficiently to afford the corresponding β-hydroxy ketones in yields up to 92a€‰%. To the best of our knowledge, this is the first report of a metal triflate acting as a safe, bench-stable, and slow-releasing source of triflic acid for the Mukaiyama aldol reaction. A diastereoselective Mukaiyama aldol reaction was performed under mild conditions with a low loading of the gallium(III) triflate catalyst (down to 0.01 mol-%). The transformation proceeded efficiently to afford the corresponding β-hydroxy ketones in yields up to 92a€‰%. Copyright
- Plancq, Baptiste,Justafort, Lyse Carole,Lafantaisie, Mathieu,Ollevier, Thierry
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supporting information
p. 6525 - 6529
(2013/11/06)
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- Method for the efficient synthesis of highly-substituted oxetan- and azetidin-, dihydrofuran- and pyrrolidin-3-ones and its application to the synthesis of (±)-pseudodeflectusin
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Highly substituted four- and five-membered heterocycles were prepared starting with O,P- and N,P-acetals by using a one-pot method involving base induced cyclization and a Horner-Wadsworth-Emmons (HWE) olefination reaction. Divergent synthesis of various heterocycles was achieved by using this method and transformations of the alkenyl group in the products of these processes were exemplified. Finally, a short and efficient synthesis of (±)- pseudodeflectusin based on the new methodology was achieved.
- Maegawa, Tomohiro,Otake, Kazuki,Hirosawa, Keiichi,Goto, Akihiro,Fujioka, Hiromichi
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supporting information
p. 4798 - 4801
(2013/01/15)
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- Direct use of esters in the Mukaiyama aldol reaction: A powerful and convenient alternative to aldehydes
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An indium triiodide catalyst promoted the direct transformation from esters to β-hydroxycarbonyl compounds using hydrosilanes and silyl enolates by a one-stage process. Various esters were applicable, and the high chemoselectivity of this system brings compatibility to many functional groups: alkenyl, alkynyl, chloro, and hydroxy.
- Inamoto, Yoshihiro,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 1168 - 1171
(2012/04/04)
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- Strong Lewis acids of air-stable metallocene bis(perfluorooctanesulfonate)s as high-efficiency catalysts for carbonyl-group transformation reactions
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Strong Lewis acids of air-stable metallocene bis(perfluorooctanesulfonate)s [M(Cp)2][OSO2C8F17] 2·nH2O·THF (M=Zr (2 a·3 H 2O·THF), M=Ti (2 b·2 H2O·THF)) were synthesized by the reaction of [M(Cp)2]Cl2 (M=Zr (1 a), M=Ti (1 b)) with nBuLi and C8F17SO3H (2 equiv) or with C8F17SO3Ag (2 equiv). The hydrate numbers (n) of these complexes were variable, changing from 0 to 4 depending on conditions. In contrast to well-known metallocene triflates, these complexes suffered no change in open air for a year. thermogravimetry-differential scanning calorimetry (TG-DSC) analysis showed that 2 a and 2 b were thermally stable at 300 and 180 °C, respectively. These complexes exhibited unusually high solubility in polar organic solvents. Conductivity measurement showed that the complexes (2 a and 2 b) were ionic dissociation in CH3CN solution. X-ray analysis result confirmed 2 a·3 H2O·THF was a cationic organometallic Lewis acid. UV/Vis spectra showed a significant red shift due to the strong complex formation between 10-methylacridone and 2 a. Fluorescence spectra showed that the Lewis acidity of 2 a fell between those of Sc3+ (λem=474 nm) and Fe3+ (λem=478 nm). ESR spectra showed the Lewis acidity of 2 a (0.91 eV) was at the same level as that of Sc3+ (1.00 eV) and Y 3+ (0.85 eV), while the Lewis acidity of 2 b (1.06 eV) was larger than that of Sc3+ (1.00 eV) and Y3+ (0.85 eV). They showed high catalytic ability in carbonyl-compound transformation reactions, such as the Mannich reaction, the Mukaiyama aldol reaction, allylation of aldehydes, the Friedel-Crafts acylation of alkyl aromatic ethers, and cyclotrimerization of ketones. Moreover, the complexes possessed good reusability. On account of their excellent catalytic efficiency, stability, and reusability, the complexes will find broad catalytic applications in organic synthesis. Copyright
- Qiu, Renhua,Xu, Xinhua,Peng, Lifeng,Zhao, Yalei,Li, Ningbo,Yin, Shuangfeng
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supporting information; experimental part
p. 6172 - 6182
(2012/06/30)
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- A family of chiral metal-organic frameworks
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Chiral metal-organic frameworks with a three-dimensional network structure and wide-open pores (>30) were obtained by using chiral trifunctional linkers and multinuclear zinc clusters. The linkers, H3ChirBTB-n, consist of a 4,4′,4′′-benzene-1,3
- Gedrich, Kristina,Heitbaum, Maja,Notzon, Andreas,Senkovska, Irena,Froehlich, Roland,Getzschmann, Juergen,Mueller, Uwe,Glorius, Frank,Kaskel, Stefan
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experimental part
p. 2099 - 2106
(2011/03/22)
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- Optically pure bulky (hetero)arylalkyl carbinols via kinetic resolution
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Planar chiral nucleophilic catalyst Fc-PIP was employed in the kinetic resolution of bulky (hetero)arylalkyl carbinols delivering unreacted alcohols with extremely high enantiomeric excess (>99.0% ees) in ideal conversions ranging from 50.4-56.7%.
- Hu, Bin,Meng, Meng,Fossey, John S.,Mo, Weimin,Hu, Xinquan,Deng, Wei-Ping
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supporting information; experimental part
p. 10632 - 10634
(2011/10/30)
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- Generation of carbanions through stibine-metal and bismuthine-metal exchange reactions and its applications to precision synthesis of ω-end-functionalized polymers
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Generation of carbanions from organostibines and organobismuthines through heteroatom-metal exchange reactions was examined from synthetic and mechanistic viewpoints. The exchange reaction proceeded spontaneously upon treatment with various organometallic reagents, such as alkyl lithiums, tetraalkyl zincates, and alkyl magnesium halides to afford the corresponding carbanions quantitatively. Due to the high reactivity of these heteroatom compounds, the exchange reactions took place exclusively even in the presence of various polar functional groups, which potentially react with organometallic species. The advantage of this method was exemplified by the end-group transformation of living polymers that bear these heteroatom species at the ω-polymer end, prepared by using organostibine and bismuthine-mediated living radical polymerizations. Various polymers that bear polar functional groups and acidic hydrogen-for example, poly(methyl methacrylate), poly(butyl acrylate), poly(N-isopropyl acrylamide), and poly(2-hydroxyethyl methacrylate)-could be used in the exchange reactions, and subsequent trapping with electrophiles afforded the corresponding polymers with controlled molecular weights, molecular weight distributions, and end-group functionalities. Competition experiments showed that organostibines and organobismuthines were among the most reactive heteroatom compounds towards organometallic reagents and that their high reactivity was responsible for the high chemoselectivity in the exchange reaction. All's well that ends well: The generation of carbanions from organostibine and -bismuthine compounds was achieved thorough a heteroatom-metal exchange reaction (see scheme). The highly chemoselective exchange reaction could be applied to precision synthesis of varieties of ω-end- functionalized polymers that possess a polar functional group.
- Kayahara, Eiichi,Yamada, Hiroto,Yamago, Shigeru
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supporting information; experimental part
p. 5272 - 5280
(2011/06/20)
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- Platinum(II) complex-catalyzed enantioselective aldol reaction with ketene silyl acetals in DMF at room temperature
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[{(R)-binap}Pt(μ-OH)]22X is a weak Lewis acid, which can catalyze the enantioselective aldol reaction of aldehydes with ketene silyl acetals in DMF at room temperature. The platinum(II) complex-catalyzed the enantioselective aldol reaction of a
- Kiyooka, Syun-ichi,Matsumoto, Satoshi,Shibata, Tomonori,Shinozaki, Kei-ichi
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experimental part
p. 1806 - 1816
(2010/04/06)
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- An E-factor minimized protocol for the preparation of methyl β-hydroxy esters
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We report the optimization of the preparation of methyl β-hydroxy esters (3a-l) in 75-93% yield by a solvent-free aldol reaction of aldehydes (1a-l) with KSA (2) followed by a de-silylation step. Amberlite IRA900F and Dowex 50Wx8 H were found to be the mo
- Fringuelli, Francesco,Lanari, Daniela,Pizzo, Ferdinando,Vaccaro, Luigi
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supporting information; scheme or table
p. 1301 - 1305
(2010/11/04)
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- Rhenium-catalyzed reaction of carbonyl compounds with ketene silyl acetals
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It was found that rhenium complex is an effective catalyst for the reaction of carbonyl compounds with ketene silyl acetals. A wide range of β-silyloxy esters is obtained by the treatment of carbonyl compounds with ketene silyl acetals in the presence of
- Nishiyama, Yutaka,Kaiba, Kenta,Umeda, Rui
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experimental part
p. 793 - 795
(2010/03/24)
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- Fluorous surface-active distannoxane catalysts
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Fluorous distannoxanes (XR2fSnOSnR2 fX)2·nH2O (Rf= C 6F13C2H4) (1: X= C8F 17SO3, n= 10; 4: X = Cl, n=
- Orita, Akihiro,Tanabe, Shoko,Ono, Tatsuhiko,Otera, Junzo
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experimental part
p. 1419 - 1423
(2010/08/19)
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- Enantioselective aldol reaction of silyl ketene acetals promoted by a Lewis base-activated Lewis acid catalyst
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The enantioselective aldol reaction of a silyl ketene acetal was promoted by chiral phosphine oxide-activated tetrachlorosilane to afford the corresponding adduct in high yield with moderate enantioselectivity.
- Shimoda, Yasushi,Tando, Teppei,Kotani, Shunsuke,Sugiura, Masaharu,Nakajima, Makoto
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experimental part
p. 1369 - 1370
(2009/11/30)
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- Mechanistic investigations of the Mukaiyama aldol reaction as a two part enantioselective reaction
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Herein, we report a mechanistic investigation of an enantioselective tandem Mukaiyama aldol reaction, consisting of a carbon-carbon bond-forming reaction and a silylation protection step in which the enantioselectivity results exclusively from the silylation step. The reaction is carried out in the presence of a Lewis base paired with a chiral quarternary ammonium salt. Mechanistic studies indicate that the enantioselectivity of the silylation step is a kinetic resolution of the aldolate intermediate. The effects of sterics and electronics on the aldehyde starting material are also presented.
- Patel, Sachin G.,Wiskur, Sheryl L.
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scheme or table
p. 1164 - 1166
(2009/06/28)
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- Catalysis of Mukaiyama aldol reactions by a tricyclic aluminum alkoxide Lewis acid
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(Chemical Equation Presented) The Mukayiama aldol reaction of aldehydes is efficiently accomplished with a low concentration of the dimeric alumatrane catalyst 2 at mild or subambient temperatures. Our protocol tolerates a wide variety of electron-rich, neutral, and deficient aryl, alkyl, and heterocyclic aldehydes. A wide variety of enol silyl ethers are also tolerated. An intermediate that was isolated provides mechanistic information regarding the role of dimeric 2 in the Mukaiyama aldol reaction. Experimental evidence is presented for the stronger Lewis acidity of 5 compared with F3B.
- Raders, Steven M.,Verkade, John G.
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supporting information; experimental part
p. 5417 - 5428
(2009/12/08)
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- P(PhCH2NCH2CH2)3N catalysis of Mukaiyama aldol reactions of aliphatic, aromatic, and heterocyclic aldehydes and trifluoromethyl phenyl ketone
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(Chemical Equation Presented) Herein we find that proazaphosphatrane 1c is a very efficient catalyst for Mukaiyama aldol reactions of aldehydes with trimethylsilyl enolates in THF solvent. Only the activated ketone 2,2,2-trifluoroacetophenone underwent clean aldol product formation with a variety of trimethylsilyl enolates under similar conditions as the aldehydes. The reactions were carried out at room temperature using (1-methoxy-2-methyl-1- propenyloxy)trimethylsilane, whereas the temperature was -15 °C in the case of 1-phenyl-1-(trimethylsilyloxy)ethylene. The reaction conditions are mild and operationally simple, and a variety of aryl functional groups, such as nitro, amino, ester, chloro, trifluoromethyl, bromo, iodo, cyano, and fluoro groups, are tolerated. Product yields are generally better than or comparable to those in the literature. 1-Phenyl-1-(trimethylsilyloxy)ethylene, 1-(trimethylsilyloxy) cyclohexene, and 2-(trimethylsilyloxy)furan underwent clean conversion to β-hydroxy carbonyl compounds under our reaction conditions. In the case of bulky (2,2-dimethyl-1-methylenepropoxy)trimethylsilane, only α,β-unsaturated esters were isolated. Heterocyclic aldehydes, such as pyridine-2-carboxaldehyde, benzofuran-2-carboxaldehyde, benzothiophene-2- carboxaldehyde, and 1-methyl-2-imidazolecarboxaldehyde, gave good yields of Mukaiyama products. An optimized synthesis for the catalyst 1c is also reported herein. 2009 American Chemical Society.
- Chintareddy, Venkat Reddy,Wadhwa, Kuldeep,Verkade, John G.
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experimental part
p. 8118 - 8132
(2010/02/28)
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- Synthesis and structure of an extremely air-stable binuclear hafnocene perfluorooctanesulfonate complex and its use in lewis acid-catalyzed reactions
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An extremely air-stable μ2-hydroxy-bridged binuclear hafonocene perfluorooctanesulfoante complex was successfully synthesized. This complex showed high catalytic efficiency in the esterification of alcohols, phenol, thiol, and amines, in the Friedel-Crafts acylation of alylaryl ethers, in the Mukaiyama aldol reaction, and in the allylation of aldehydes and could be reused.
- Qiu, Renhua,Zhang, Guoping,Zhu, Yuyang,Xu, Xinhua,Shao, Lingling,Li, Yinhui,An, Delie,Yin, Shuangfeng
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supporting information; experimental part
p. 6488 - 6494
(2010/02/28)
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- NO cations as highly efficient catalysts for carbon-carbon bond forming reactions
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NO cations were found to be a highly effective catalysts in several carbon-carbon bond forming reactions. For example, [3 + 2] cycloadditions of nitrones or azomethine imines with vinyl ethers proceeded in the presence of 0.1-1 mol % of the NO cation to afford the desired adducts in high yields. Copyright
- Yamashita, Yasuhiro,Kobayashi, Shue
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supporting information; scheme or table
p. 678 - 679
(2011/04/22)
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- (μ-Hydroxo)-platinum complex-catalyzed enantioselective aldol reaction of aldehydes with 1-methoxy-2-methyl-1-(trimethylsilyloxy)propene in DMF
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[((R)-BINAP)Pt(μ-OH)]2·2OTf catalyzed the enantioselective aldol reaction of aldehydes with 1-methoxy-2-methyl-(1-trimethylsilyloxy)propene at room temperature in dry DMF in high yields with enantioselectivity up to 92%. This is a versatile exa
- Kiyooka, Syun-ichi,Matsumoto, Satoshi,Kojima, Masafumi,Sakonaka, Kazuyuki,Maeda, Hirofumi
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p. 1589 - 1592
(2008/09/18)
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- Synthesis of new C1-symmetric bis(oxazoline) ligands with a chelating sidearm for stereoselective Mukaiyama aldol condensations
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Novel C1-symmetric bis(oxazoline) ligands with a secondary binding sidearm were prepared in enantiomerically pure form in good yields, in only four steps starting from commercially available reagents. These new chiral ligands were tested in the
- Orlandi, Simonetta,Benaglia, Maurizio,Dell'Anna, Gianmaria,Celentano, Giuseppe
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p. 2120 - 2124
(2007/10/03)
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- Storable, powdered chiral zirconium complex for asymmetric aldol and hetero Diels-Alder reactions
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A storable, powdered chiral zirconium catalyst for asymmetric aldol and hetero Diels-Alder reactions has been developed. The catalyst has the same activity as that prepared in situ even after being stored for 3 months. Moreover, this chiral Zr catalyst wo
- Seki, Kazutaka,Ueno, Masaharu,Kobayashi, Shu
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p. 1347 - 1350
(2008/01/01)
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- N-heterocyclic carbene-catalyzed Mukaiyama aldol reactions
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(Chemical Equation Presented) N-Heterocyclic carbenes were shown to be highly effective catalysts to promote Mukaiyama aldol reactions. In the presence of only 0.5 mol % of N-heterocyclic carbene (5), various aldehydes and 2,2,2-trifluoroacetophenone unde
- Song, Jinhua J.,Tan, Zhulin,Reeves, Jonathan T.,Yee, Nathan K.,Senanayake, Chris H.
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p. 1013 - 1016
(2007/10/03)
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- Catalytic enantioselective Mukaiyama aldol reaction via a chiral indium(III)-pybox complex
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A chiral indium(III) complex prepared from indium triflate and a pybox ligand has been developed to give good yields and enantioselectivities (up to 92% ee) in the addition of (1-methoxy-2-methyl-propenyloxy)-trimethylsilane to various aromatic and alipha
- Fu, Fan,Teo, Yong-Chua,Loh, Teck-Peng
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p. 4267 - 4269
(2007/10/03)
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- Organotin perfluorooctanesulfonates as air-stable Lewis acid catalysts: Synthesis, characterization, and catalysis
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The reactions of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane and di-alkyltin dihalides with silver perfluoro-octanesulfonate provided the corresponding sulfonates as hydrates. The number of water molecules (n) of hydration was dependent on the conditions. The distannoxane derivative was identified as n from 0.5 to 6, while in the hydrated mononuclear species and DMSO complexes n varied widely from 4 to 13. 119Sn NMR spectroscopy and conductivity measurements indicated the ionic dissociation of these compounds in solution. These compounds exhibited unusually high solubility in polar organic solvents. The ionic dissociation together with facile hydration probably causes the unusual solubility. The Lewis acidity of these compounds was found to be high among organotin derivatives on the basis of ESR spectra of Superoxide/ metal-ion complexes. In contrast to well-known organotin Inflates, these compounds suffered no hydrolysis upon storage in open air. The high catalytic activity of the distannoxane 1 was exemplified for various carboncarbon bond-forming reactions, such as Mukaiyama-aldol as well as -Michael reactions and allylation of aldehydes.
- An, De Lie,Peng, Zhihong,Orita, Akihiro,Kurita, Akinobu,Man-E, Sumiyo,Ohkubo, Kei,Li, Xingshu,Fukuzumi, Shunichi,Otera, Junzo
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p. 1642 - 1647
(2007/10/03)
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- Practical aldol reaction of trimethylsilyl enolate with aldehyde catalyzed by N-methylimidazole as a Lewis base catalyst
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Aldol reaction of trimethylsilyl enolate with aldehyde proceeded in the presence of a catalytic amount of a Lewis base, N-methylimidazole, and lithium chloride in DMF at room temperature. Not only aryl aldehyde but also alkyl aldehyde provided the aldol p
- Hagiwara, Hisahiro,Inoguchi, Hideyuki,Fukushima, Masakazu,Hoshi, Takashi,Suzuki, Toshio
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p. 5371 - 5373
(2007/10/03)
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- With molecular-oxygen-activated Lewis acids: Dinuclear molybdenum complexes for aza-Diels-Alder reactions of acyl hydrazones
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(Chemical Equation Presented) Easy activation: A Lewis acid catalyst based on molybdenum relies on activation by molecular oxygen for its high catalytic activity. The novel complex catalyzes the aza-Diels-Alder reaction of acyl hydrazones with Danishefsky
- Yamashita, Yasuhiro,Salter, Matthew M.,Aoyama, Kayoko,Kobayashi, Shu
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p. 3816 - 3819
(2007/10/03)
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- Lewis base catalyzed mannich-type reactions between trimethylsilyl enol ethers and aldimines
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Lewis base catalyzed Mannich-type reaction between trimethylsilyl enol ethers and N-tosylaldimines is described. Nitrogen anions generated from amides or imides such as lithium benzamide or potassium phthalimide are found to be effective Lewis base cataly
- Fujisawa, Hidehiko,Takahashi, Eiki,Mukaiyama, Teruaki
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p. 5082 - 5093
(2008/02/10)
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- Lewis base activation of Lewis acids: Catalytic, enantioselective addition of silyl ketene acetals to aldehydes
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The concept of Lewis base activation of Lewis acids has been reduced to practice for catalysis of the aldol reaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl4), can b
- Denmark, Scott E.,Beutner, Gregory L.,Wynn, Thomas,Eastgate, Martin D.
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p. 3774 - 3789
(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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- Aldol reaction of trimethylsilyl enolate with aldehyde catalyzed by pyridine N-oxide as a Lewis base catalyst
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Aldol reaction of trimethylsilyl enolate with aldehydes proceeded in the presence of a catalytic amount of a Lewis base, pyridine N-oxide, and lithium chloride in DMF at room temperature. Not only aryl aldehydes but also alkyl aldehydes provided the aldol
- Hagiwara, Hisahiro,Inoguchi, Hideyuki,Fukushima, Masakazu,Hoshi, Takashi,Suzuki, Toshio
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p. 2388 - 2390
(2007/10/03)
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- An environmentally friendly procedure for Mukaiyama aldol and Mukaiyama-Michael reactions using a catalytic amount of DBU under solvent- and metal-free conditions
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Mukaiyama aldol and Mukaiyama-Michael reactions can proceed smoothly in the presence of a catalytic amount of DBU (20% mmol), to afford the corresponding products in moderate to good yields. This solvent- and metal-free approach provides an environmentall
- Shen, Zhi-Liang,Ji, Shun-Jun,Loh, Teck-Peng
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p. 507 - 508
(2007/10/03)
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- Enantioselective catalysis in water: Mukaiyama-aldol condensation promoted by copper complexes of bisoxazolines supported on poly(ethylene glycol)
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(S)-3-Phenyl-2-aminopropanol-derived bisoxazolines supported on a modified poly(ethylene glycol) were shown to be effective Cu(II) ligands for the enantioselective Mukaiyama-aldol condensation of various aldehydes with the trimethylsilyl keteneacetal of m
- Benaglia, Maurizio,Cinquini, Mauro,Cozzi, Franco,Celentano, Giuseppe
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p. 3401 - 3407
(2007/10/03)
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- Lithium acetate-catalyzed aldol reaction between aldehyde and trimethylsilyl enolate in anhydrous or water-containing N,N-dimethylformamide
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Lithium acetate (AcOLi)-catalyzed aldol reactions between trimethylsilyl enolates and aldehydes proceed smoothly in anhydrous DMF or pyridine to afford the corresponding aldols in good to high yields under weakly-basic conditions (Tables 1-5). This cataly
- Nakagawa, Takashi,Fujisawa, Hidehiko,Nagata, Yuzo,Mukaiyama, Teruaki
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p. 1555 - 1567
(2007/10/03)
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- (2,7-Disubstituted-1,8-biphenylenedioxy)bis(dimethylaluminum) as Bidentate Organoaluminum Lewis Acids: Elucidation and Synthetic Utility of the Double Electrophilic Activation Phenomenon
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A series of (2,7-disubstituted-1,8-biphenylenedioxy)bis(dimethylaluminum) (2) has been readily prepared in situ by treatment of the requisite 2,7-disubstituted-1,8-biphenylenediol (1) with Me3Al (2 equiv) in CH2Cl2 at room temperature; this primarily relies on the successful establishment of a new synthetic procedure of 1 starting from inexpensive m-anisidine. Evaluation of 2 as a bidentate organoaluminum Lewis acid has been performed by the reduction of ketonic substrates using Bu 3SnH as a hydride source in comparison to the conventional monodentate Lewis acid dimethylaluminum 2,6-xylenoxide (11), uncovering the significantly high activation ability of 2 toward carbonyl. Particularly, (2,7-dimethyl-1,8-biphenylenedioxy)-bis(dimethylaluminum) (2a) exerted the highest reactivity, which has also been emphasized in the Mukaiyama aldol reaction. The structure of the bidentate Lewis acid 2 was unambiguously determined by single-crystal X-ray diffraction analysis of 2g possessing a bulky 3,5-di-tert-butylphenyl substituent, revealing the rigid dimeric assembly in the solid state. The double electrophilic activation of carbonyl substrate by 2a has been supported by low-temperature 13C NMR analysis as well as theoretical study using the Gaussian 98 program. Moreover, unique stereoselectivity has been observed in the 2a-promoted Mukaiyama Michael addition, and highly chemoselective functionalization of carbonyl compounds in the presence of their acetal counterparts has been realized using 2a. Finally, the effectiveness of 2a for the activation of ether functionality has been demonstrated in the Claisen rearrangement of allyl vinyl ethers.
- Ooi, Takashi,Takahashi, Makoto,Yamada, Masao,Tayama, Eiji,Omoto, Kiyoyuki,Maruoka, Keiji
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p. 1150 - 1160
(2007/10/03)
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- Product-catalyzed aldol reaction between trimethylsilyl enolates and aldehydes
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Aldol reactions between trimethylsilyl ketene acetals and aldehydes by using a catalytic amount of alkoxide anion proceeded smoothly to afford the corresponding aldols in DMF, indicating that the initially-formed aldolate anion effectively worked to catal
- Fujisawa, Hidehiko,Nakagawa, Takashi,Mukaiyama, Teruaki
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p. 1241 - 1246
(2007/10/03)
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- Hydrophobic polymer-supported scandium catalyst for carbon-carbon bond-forming reactions in water
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It has been revealed that a hydrophobic polymer-supported scandium(III) catalyst prepared from sulfonated polystyrene resin is an effective catalyst for carbon-carbon bond-forming reactions such as Mukaiyama aldol reactions in water. According to studies
- Iimura, Shinya,Manabe, Kei,Kobayashi, Shu
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p. 7673 - 7678
(2007/10/03)
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- Mukaiyama Aldol Reactions of Silyl Enolates Catalyzed by Iodine
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Iodine catalyzed Mukaiyama aldol reaction of silyl enol ethers and silyl ketene acetal with aldehydes, ketones and acetals in good yield with preferential antiselectivity has been described.
- Phukan, Prodeep
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p. 1065 - 1070
(2007/10/03)
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- Mukaiyama aldol reaction using ketene silyl acetals with carbonyl compounds in ionic liquids
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Mukaiyama aldol reactions using ketene silyl acetals with various aldehydes proceed smoothly in ionic liquids to afford the corresponding aldol products in moderate yields.
- Chen, Shui-Ling,Ji, Shun-Jun,Loh, Teck-Peng
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p. 375 - 377
(2007/10/03)
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- Lewis base activation of Lewis acids. Vinylogous aldol reactions
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A highly regioselective vinylogous aldol reaction catalyzed by SiCl4 and a chiral phosphoramide (R,R)-5, providing δ-hydroxy enones for a variety of aldehyde and dienol ether structures, has been developed. Low catalyst loadings (1 mol %) can b
- Denmark, Scott E.,Beutner, Gregory L.
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p. 7800 - 7801
(2007/10/03)
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- 'Fluorous nanoflow' system for the Mukaiyama aldol reaction catalyzed by the lowest concentration of the lanthanide complex with bis(perfluorooctanesulfonyl)amide ponytail
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'Fluorous nanoflow' system is extremely effective for the lanthanide bis(perfluorooctanesulfonyl)amide-catalyzed Mukaiyama aldol reaction with dramatic increase in the reaction rate by the continuously controlled nano feeder. Thus, the acceleration of the
- Mikami, Koichi,Yamanaka, Masahiro,Islam, Md. Nazrul,Kudo, Kenichi,Seino, Nobuko,Shinoda, Masaki
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p. 10593 - 10597
(2007/10/03)
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- Lithium acetate-catalyzed aldol reaction between aldehyde and trimethylsilyl enolate
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Lithium acetate-catalyzed aldol reaction between trimethylsilyl enolates and aldehydes proceeded smoothly in a DMF or pyridine solvent to afford the corresponding aldols in good to high yields under weakly basic conditions.
- Nakagawa, Takashi,Fujisawa, Hidehiko,Mukaiyama, Teruaki
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p. 462 - 463
(2007/10/03)
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- Some uses of mischmetall in organic synthesis
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Mischmetall, an alloy of the light lanthanides, has been used in a variety of organic reactions, either as a coreductant in samarium(II)-mediated reactions (Barbier and Grignard-type reactions, pinacolic coupling reactions) or as the promoter of Reformatsky-type reactions. It has been also employed as the starting material for easy syntheses of lanthanide trihalides, the reactivity of which has been explored in Imamoto and Luche-Fukuzawa reactions and in Mukaiyama aldol reactions.
- Lannou, Marie-Isabelle,Hélion, Florence,Namy, Jean-Louis
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p. 10551 - 10565
(2007/10/03)
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- Lithium Acetate Catalyzed Aldol Reaction between Aldehyde and Trimethylsilyl Enolate in a Dimethylformamide-H2O Solvent
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Lithium acetate catalyzed aldol reaction between trimethylsilyl enolates and aldehydes in a DMF-H2O (50:1) solvent proceeded smoothly to afford the corresponding aldols in good to high yields. It is noted that trimethylsilyl enolates derived fr
- Nakagawa, Takashi,Fujisawa, Hidehiko,Mukaiyama, Teruaki
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p. 696 - 697
(2007/10/03)
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