- Hydroperoxidations of Alkenes using Cobalt Picolinate Catalysts
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Hydroperoxides were synthesized in one step from various alkenes using Co(pic)2as the catalyst with molecular oxygen and tetramethyldisiloxane (TMDSO). The hydration product could be obtained using a modified catalyst, Co(3-mepic)2, with molecular oxygen and phenylsilane. Formation of hydroperoxides occurred through a rapid Co-O bond metathesis of a peroxycobalt compound with isopropanol.
- Peralta-Neel, Zulema,Woerpel
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supporting information
p. 5002 - 5006
(2021/06/30)
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- Visible-Light-Driven, Metal-Free Divergent Difunctionalization of Alkenes Using Alkyl Formates
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In recent decades, difunctionalization of alkenes has received considerable attention as an efficient and straightforward way to increase molecular complexity. However, examples of the difunctionalization of alkenes initiated by the intermolecular addition of alkoxycarbonyl radicals providing substituted alkanoates are still rare. Herein, we present the visible light-driven metal-free divergent difunctionalization of alkenes triggered by the intermolecular addition of alkoxycarbonyl radicals under ambient conditions. Employing alkyl formates as precursors of alkoxycarbonyl radicals and 4CzIPN as the photocatalyst, a variety of substituted alkanoates, including β-alkoxy, β-hydroxy, β-dimethoxymethoxy, and β-formyloxy alkanoates, could be facilely accessed with high functional group tolerance and high efficiency. Moreover, the mechanism study revealed that β-hydroxy alkanoates were generated by a selective decomposition of orthoformates promoted by the N-alkoxyazinium salt.
- Zheng, Ming,Hou, Jing,Zhan, Le-Wu,Huang, Yan,Chen, Ling,Hua, Li-Li,Li, Yan,Tang, Wan-Ying,Li, Bin-Dong
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p. 542 - 553
(2021/01/14)
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- Pentamethylphenyl (Ph*) and Related Derivatives as Useful Acyl Protecting Groups for Organic Synthesis: A Preliminary Study
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A study of acyl protecting groups derived from the Ph? motif is reported. While initial studies indicated that a variety of functional groups were not compatible with the Br 2-mediated cleavage conditions required to release the Ph? group, strategies involving the use of different reagents or a modification of Ph? itself (Ph*OH) were investigated to solve this problem.
- Cheong, Choon Boon,Frost, James R.,Donohoe, Timothy J.
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p. 1828 - 1832
(2020/10/06)
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- One-pot enol silane formation-Mukaiyama aldol reactions: Crossed aldehyde-aldehyde coupling, thioester substrates, and reactions in ester solvents
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Trimethylsilyl trifluoromethanesulfonate (TMSOTf) and a trialkylamine base promote both in situ enol silane/silyl ketene acetal formation and Mukaiyama aldol addition reactions between a variety of reaction partners in a single reaction flask. Isolation of the required enol silane or silyl ketene acetal is not necessary. For example, crossed aldol reactions between α-disubstituted aldehydes and non-enolizable aldehydes yield β-hydroxy aldehydes in good yield. In a related reaction, the common laboratory solvent ethyl acetate functions as both an enolate precursor and a green reaction solvent. When thioesters are employed as enolate precursors, high yields for additions to non-enolizable aldehydes are routinely observed.
- Downey, C. Wade,Dixon, Grant J.,Ingersoll, Jared A.,Fuller, Claire N.,MacCormac, Kenneth W.,Takashima, Anna,Sediqui, Rohina
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supporting information
(2019/10/14)
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- Chiral Nitroarenes as Enantioselective Single-Electron-Transfer Oxidants for Carbene-Catalyzed Radical Reactions
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A new class of chiral oxidants is developed. These readily accessible oxidants contain a nitro group for oxidation and a chiral sulfonamide moiety for stereoselectivity control. The chiral information from the oxidants can effectively transfer to the substrates in carbene-catalyzed β-hydroxylation of enals via single-electron-transfer radical processes. We expect these oxidants to find unique applications in other asymmetric oxidations and oxygen-atom-transferring reactions.
- Wang, Hongling,Wang, Yuhuang,Chen, Xingkuan,Mou, Chengli,Yu, Shuyan,Chai, Huifang,Jin, Zhichao,Chi, Yonggui Robin
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supporting information
p. 7440 - 7444
(2019/10/02)
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- A Ball-Milling-Enabled Reformatsky Reaction
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An operationally simple one-jar one-step mechanochemical Reformatsky reaction using in situ generated organozinc intermediates under neat grinding conditions has been developed. Notable features of this reaction protocol are that it requires no solvent, no inert gases, and no pre-activation of the bulk zinc source. The developed process is demonstrated to have good substrate scope (39–82 % yield) and is effective irrespective of the initial morphology of the zinc source.
- Cao, Qun,Stark, Roderick T.,Fallis, Ian A.,Browne, Duncan L.
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p. 2554 - 2557
(2019/06/17)
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- Method for preparing organoboron compound under catalytic effect of chitosan immobilized copper and application
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The invention discloses a method for preparing an organoboron compound under a catalytic effect of chitosan immobilized copper and an application. The method comprises the following steps: A) adding a chitosan immobilized copper catalyst and a ligand into a reaction tube and stirring; B) respectively continuously adding an initial raw material I and bisdiboron into a system in turn; C) stirring the whole reaction system and reacting under room temperature; D) after the reaction is ended, filtering the whole reaction system, washing with tetrahydrofuran, performing rotary evaporation and concentration on a filtrate, adopting a mixed solvent of ethyl acetate and petroleum ether at different ratios for performing column chromatography on the residues, separating and purifying, thereby acquiring a target product II. The silica gel is taken as a fixing phase for column chromatography. The invention also relates to the application of the prepared organoboron compound in compounding beta-hydroxy compound and anti-cancer drug molecules. The method is feasible; the operation is simple and convenient; the method is suitable for various substrates and can be used for successfully preparing the corresponding target compounds. The catalyst is low in dosage and is recyclable, is easily separated after the ending of the reaction, is free from metal residue and is suitable for large-scale production.
- -
-
Paragraph 0135; 0136; 0137; 0138; 0139; 0140
(2017/07/21)
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- A green and recyclable chitosan supported catalyst for the borylation of α,β-unsaturated acceptors in water
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We herein report a green and recyclable chitosan supported copper catalyst which is capable of catalyzing the borylation of α,β-unsaturated acceptors in water at room temperature. A broad substrate scope including chalcone derivatives, esters and nitriles have been explored. In all the cases, desired products were obtained in good to excellent yields. Remarkably, this chitosan supported catalyst could be recovered and reused for five times without any significant decrease of reactivity.
- Xu, Pengyu,Li, Bojie,Wang, Liansheng,Qin, Caiqin,Zhu, Lei
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- Homoserine lactone derivatives, preparation method thereof and pharmaceutical composition for prevention or treatment of the periodontal diseases containing the same as an active ingredient
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The present invention relates to homoserine lactone derivatives, optical isomers of the same, or pharmaceutically acceptable salts of the same. The homoserine lactone derivatives in the present invention have excellent properties as a quorum sensing antagonist which hinders communications among bacteria. According to the present invention, the homoserine lactone derivatives can hinder gene expressions of bacteria while effectively blocking formation of biofilm which is known to raise resistance against antibiotics, and suppress propagation of bacteria, thereby being useful as a pharmaceutical composition for preventing or treating periodontal diseases.
- -
-
Paragraph 0147-0150
(2017/04/14)
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- Ligand-Promoted, Boron-Mediated Chemoselective Carboxylic Acid Aldol Reaction
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The first carboxylic acid selective aldol reaction mediated by boron compounds and a mild organic base (DBU) was developed. Inclusion of electron-withdrawing groups in the amino acid derivative ligands reacted with BH3·SMe2 forms a boron promoter with increased Lewis acidity at the boron atom and facilitated the carboxylic acid selective enolate formation, even in the presence of other carbonyl groups such as amides, esters, ketones, or aliphatic aldehydes. The remarkable ligand effect led to the broad substrate scope including biologically relevant compounds.
- Nagai, Hideoki,Morita, Yuya,Shimizu, Yohei,Kanai, Motomu
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p. 2276 - 2279
(2016/06/01)
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- Development of an axially chiral sp3P/sp3NH/sp2N-combined linear tridentate ligand - Fac-selective formation of Ru(II) complexes and application to ketone hydrogenation
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A newly developed chiral linear tridentate ligand, R-PN(H)N (R=H or Ph), possesses Ph2P and PyCH2NH groups at C(2) and C(2′) positions of the 1,1′-binaphthyl skeleton without or with a C(3)-Ph substituent. The steric effect of C(3)-Ph and the electronic effect of the DMSO co-ligand realize the facial selective generation of fac-RuCl2(Ph-PN(H)N)(dmso) and fac-[Ru(H-PN(H)N)(dmso)3](BF4)2, respectively. Both an H-Ru?sp3N-H reaction site responsible for the donor-acceptor bifunctional catalyst (DACat) and a fence/plane chiral context were constructed by means of the following advantageous points: i) the sp3P, sp3N, and sp2N ligating atoms have different electronic properties; ii) DMSO trans to sp3N strongly coordinates to Ru and is fixed by a PyC(6)H?O=S hydrogen bond; and iii) the single NH function simplifies the DACat reaction site. The synergistic effect has led to success in the asymmetric hydrogenation of sterically demanding ketones. Structural characteristics of first-row transition metal complexes of R-PN(H)N have been also investigated.
- Yamamura, Tomoya,Nakane, Satoshi,Nomura, Yuko,Tanaka, Shinji,Kitamura, Masato
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supporting information
p. 3781 - 3789
(2016/06/06)
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- Ar-BINMOL-derived salan-Cu(II) complex-catalyzed silyl-reformatsky reaction of aromatic aldehydes
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In this work, we have developed a facile protocol with salan-Cu system for the facile and selective synthesis of β-hydroxyesters via silyl-Reformatsky reaction with -silylester and aldehydes. The screening and optimization of reaction conditions led to the determination of a practical and efficient procedure in which the salan-Cu exhibited promising catalytic activity in dimethylsulfoxide, in which the silyl-Reformatsky reaction of aromatic aldehydes with -trimethylsilylmethylacetate gave the corresponding β-hydroxyester derivatives in excellent yields (up to 98%) under fluoride-free reaction conditions.
- Li, Fei,Zhou, Wei,Zheng, Long-Sheng,Li, Li,Zheng, Zhan-Jiang,Xu, Li-Wen
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supporting information
p. 2861 - 2869
(2014/09/17)
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- Steric vs. electronic effects in the Lactobacillus brevis ADH-catalyzed bioreduction of ketones
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Lactobacillus brevis ADH (LBADH) is an alcohol dehydrogenase that is commonly employed to reduce alkyl or aryl ketones usually bearing a methyl, an ethyl or a chloromethyl as a small ketone substituent to the corresponding (R)-alcohols. Herein we have tested a series of 24 acetophenone derivatives differing in their size and electronic properties for their reduction employing LBADH. After plotting the relative activity against the measured substrate volumes we observed that apart from the substrate size other effects must be responsible for the activity obtained. Compared to acetophenone (100% relative activity), other small substrates such as propiophenone, α,α, α-trifluoroacetophenone, α-hydroxyacetophenone, and benzoylacetonitrile had relative activities lower than 30%, while medium-sized ketones such as α-bromo-, α,α-dichloro-, and α,α-dibromoacetophenone presented relative activities between 70% and 550%. Moreover, the comparison between the enzymatic activity and the obtained final conversions using an excess or just 2.5 equiv. of the hydrogen donor 2-propanol, denoted again deviations between them. These data supported that these hydrogen transfer (HT) transformations are mainly thermodynamically controlled. For instance, bulky α-halogenated derivatives could be quantitatively reduced by LBADH even employing 2.5 equiv. of 2-propanol independently of their kinetic values. Finally, we found good correlations between the IR absorption band of the carbonyl groups and the degrees of conversion obtained in these HT processes, making this simple method a convenient tool to predict the success of these transformations. The Royal Society of Chemistry.
- Rodriguez, Cristina,Borzecka, Wioleta,Sattler, Johann H.,Kroutil, Wolfgang,Lavandera, Ivan,Gotor, Vicente
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supporting information
p. 673 - 681
(2014/01/06)
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- Oxone-mediated oxidative cleavage of β-keto esters and 1,3-diketones to α-keto esters and 1,2-diketones in aqueous medium
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A versatile and highly efficient method for the direct synthesis of α-keto esters and 1,2-diketones has been developed. This approach utilizes the oxidative cleavage of a variety of β-keto esters and 1,3-diketones mediated by an Oxone/aluminum trichloride system. The simple one-step oxidation reaction proceeded selectively in aqueous media to afford products in high yields, short reaction times, and environmentally benign conditions.
- Stergiou, Anastasios,Bariotaki, Anna,Kalaitzakis, Dimitris,Smonou, Ioulia
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p. 7268 - 7273
(2013/08/15)
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- Studies on the chemoenzymatic synthesis of (R)- and (S)-methyl 3-aryl-3-hydroxypropionates: The influence of toluene-pretreatment of lipase preparations on enantioselective transesterifications
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Two series (para- and meta-substituted) of racemic methyl esters of 3-aryl-3-hydroxypropionic acid were prepared after which the enantiomers were separated by an enzyme-catalyzed transesterification. Several lipases were investigated as the catalyst. The influence of the enzyme pretreatment, as well as substrate concentration, reaction temperature, stirring manner, and substrate conversion on the stereochemical outcome of the biotransformation process were investigated in detail. The best results were achieved by using solvent-pretreated lipase from Pseudomonas fluorescens or Burkholderia cepacia suspended in toluene, and vinyl acetate as the acetyl group donor.
- Borowiecki, Pawel,Bretner, Maria
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p. 925 - 936
(2013/09/23)
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- Metal or ammonium alginates as Lewis base catalysts for the 1,2-addition of silyl nucleophiles to carbonyl compounds
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Several metal (Na+, Ca2+) or ammonium (n-Bu 4N+) derivatives of alginic acid, an abundant bio-polymer obtained from the cell walls of brown algae, were synthesized. Their potential to act as organocatalysts to catalyze the 1,2-addition of various silyl derivatives to carbonyl compounds was evaluated for the first time. Ammonium alginate 1h is able to promote the reaction in modest to good isolated yields (up to 98%) affording access to a large range of substrates (β-cyano alcohols or ester, β-substituted methylacrylate or acrylonitrile, and cyanohydrin) by using only 5 mol % of catalyst.
- Verrier, Cécile,Oudeyer, Sylvain,Dez, Isabelle,Levacher, Vincent
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supporting information; experimental part
p. 1958 - 1960
(2012/05/19)
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- Magnetic nanoparticles entrapped in siliceous mesocellular foam: A new catalyst support
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γ-Fe2O3 nanoparticles were formed inside the cage-like pores of mesocellular foam (MCF). These magnetic nanoparticles showed a uniform size distribution that could be easily controlled by the MCF pore size, as well as by the hydrocarbon chain length used for MCF surface modification. Throughout the entrapment process, the pore structure and surface area of the MCF remained intact. The resulting magnetic MCF facilitated the immobilization of biocatalysts, homogeneous catalysts, and nanoclusters. Moreover, the MCF allowed for facile catalyst recovery by using a simple magnet. The supported catalysts exhibited excellent catalytic efficiencies that were comparable to their homogeneous counterparts. Copyright
- Lee, Su Seong,Riduan, Siti Nurhanna,Erathodiyil, Nandanan,Lim, Jaehong,Cheong, Jian Liang,Cha, Junhoe,Han, Yu,Ying, Jackie Y.
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experimental part
p. 7394 - 7403
(2012/07/27)
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- Cobalt oxide supported gold nanoparticles as a stable and readily-prepared precursor for the in situ generation of cobalt carbonyl like species
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A treatment of cobalt oxide supported gold nanoparticles (Au/Co 3O4) under syngas atmosphere effectively generated a cobalt carbonyl-like active species in the reaction vessel. The preparation of Au/Co3O4 was quite simple and the in situ generated cobalt species could be used as a stable and easy handling alternative for dicobalt octacarbonyl without bothersome purification prior to use. The reactions, which are sensitive to the purity of the dicobalt octacarbonyl, such as the alkoxycarbonylation of epoxides and the Pauson-Khand reaction, smoothly progressed with Au/Co3O4.
- Hamasaki, Akiyuki,Muto, Akiko,Haraguchi, Shingo,Liu, Xiaohao,Sakakibara, Takanori,Yokoyama, Takushi,Tokunaga, Makoto
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supporting information; experimental part
p. 6869 - 6872
(2012/02/05)
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- Iron-catalyzed oxidative addition of alkoxycarbonyl radicals to alkenes with carbazates and air
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Clean and simple: Alkoxycarbonyl radicals generated from carbazates by iron catalysis in air underwent addition to a variety of alkenes to give the corresponding β-hydroxyesters (see scheme). The simple experimental procedure for this transformation has the added advantage that the reagents are environmentally friendly. R1,R2=alkyl, alkynyl, aryl, CO2Et; [Fe(Pc)]=iron phthalocyanine. Copyright
- Taniguchi, Tsuyoshi,Sugiura, Yuki,Zaimoku, Hisaaki,Ishibashi, Hiroyuki
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supporting information; experimental part
p. 10154 - 10157
(2011/02/24)
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- Dynamic kinetic resolution of α-chloro β-keto esters and phosphonates: Hemisynthesis of Taxotere through Ru-DIFLUORPHOS asymmetric hydrogenation
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The dynamic kinetic resolution (DKR) of racemic α-chloro β-ketoesters and α-chloro β-ketophosphonates through ruthenium-mediated asymmetric hydrogenation is reported. The corresponding α-chloro β-hydroxyesters and α-chloro β- hydroxyphosphonates were obtained in good to high enantio- and diastereomeric excesses using, in particular, the atropisomeric ligand DIFLUORPHOS. This methodology allowed an efficient preparation of the anti phenylisoserine side chain of Taxotere which has been used for the hemisynthesis of the cancer therapeutic agent itself. In addition, 13C NMR in chiral oriented solvents was used to investigate the DKR effect.
- Prevost, Sebastien,Gauthier, Sebastien,De Andrade, Maria Cristina Cano,Mordant, Celine,Touati, Ali Rhida,Lesot, Philippe,Savignac, Philippe,Ayad, Tahar,Phansavath, Phannarath,Ratovelomanana-Vidal, Virginie,Genet, Jean-Pierre
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experimental part
p. 1436 - 1446
(2010/11/03)
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- Reduction of aromatic and aliphatic keto esters using sodium borohydride/MeOH at room temperature: a thorough investigation
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Reduction of keto esters is a valuable alternative to produce diols. Sodium borohydride/MeOH system at room temperature and short reaction time efficiently reduced α, β, γ, and δ-keto esters having α-keto esters as the most reactive. The ester functionality was reduced effectively due to the presence of oxo group that somehow facilitates the formation of ring intermediate. As expected, the chemoselective experiments showed that ester functionality was not reduced using this system. This study presents a simple, easy, and benign reduction process of various keto esters to its corresponding diols.
- Kim, Juryoung,De Castro, Kathlia A.,Lim, Minkyung,Rhee, Hakjune
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supporting information; experimental part
p. 3995 - 4001
(2010/07/05)
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- PALLADIUM CATALYSTS
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The invention relates to a particulate substance comprising a particulate porous support coupled to a palladium species. The palladium species may comprise palladium nanoclusters. The particulate substance may be used as a catalyst for conducting a carbon-carbon coupling reaction or a reduction.
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Page/Page column 13; 19
(2010/05/13)
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- B(OMe)3 as a nonacidic iminium ion generator in Mannich- and Ugi-type reactions
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Mannich-type reactions of aldehydes with secondary amines and a ketene silyl acetal were promoted by trimethoxyborane in DMSO to afford the corresponding β-amino esters in good yields. B(OMe)3 also promoted Ugi-type reactions of aldehydes with
- Tanaka, Yusuke,Hidaka, Kousuke,Hasui, Tomoaki,Suginome, Michinori
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body text
p. 1148 - 1151
(2009/07/11)
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- Palladium nanoclusters supported on propylurea-modified siliceous mesocellular foam for coupling and hydrogenation reactions
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This paper describes the synthesis, characterization and applications of palladium (Pd) nanoparticles supported on siliceous mesocellular foam (MCF). Pd nanoparticles of 2-3 nm and 4-6 nm were used in reactions involving molecular hydrogen (such as hydrogenation of double bonds and reductive amination), transfer hydrogenation of ketones and epoxides, and coupling reactions (such as Heck and Suzuki reactions). They successfully catalyzed all these reactions with excellent yield and selectivity. This heterogeneous catalyst was easily recovered by filtration, and recycled several times without any significant loss in activity and selectivity. The palladium leaching in the reactions was determined to be much less than the FDA-approved limit of 5 ppm. Furthermore, the catalyst can be stored and handled under normal atmospheric conditions. This immobilized catalyst allows for ease of recovery/reuse and minimization of waste generation, which are of great interest in the development of green chemical processes.
- Erathodiyil, Nandanan,Ooi, Samuel,Seayad, Abdul M.,Han, Yu,Lee, Su Seong,Ying, Jackie Y.
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experimental part
p. 3118 - 3125
(2009/04/08)
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- Deracemisation of β-hydroxy esters using immobilised whole cells of Candida parapsilosis ATCC 7330: substrate specificity and mechanistic investigation
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Deracemisation of aryl substituted β-hydroxy esters by immobilised whole cells of Candida parapsilosis ATCC 7330 gave >99% ee and up to 75% yield of their corresponding (S)-enantiomers. Mechanistic investigation of the deracemisation reaction carried out using a deuterated substrate, ethyl 3-deutero-3-hydroxy-3-phenyl propanoate revealed that while the (S)-enantiomer remains unreacted the (R)-enantiomer undergoes enantioselective oxidation to its corresponding ketoester, which on complementary enantiospecific reduction gives the (S)-enantiomer in high yield and % ee.
- Padhi, Santosh Kumar,Titu,Pandian, N. Ganesh,Chadha, Anju
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p. 5133 - 5140
(2007/10/03)
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- An improved asymmetric Reformatsky reaction mediated by (-)-N,N-dimethylaminoisoborneol
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(-)-N,N-Dimethylaminoisoborneol ((-)-DAIB) was found to be an excellent ligand for the enantioselective addition of Reformatsky reagents to aromatic and aliphatic aldehydes. Enantioselectivities up to 93% ee were obtained with sulfur-containing aldehydes.
- Kloetzing, Ralf J.,Thaler, Tobias,Knochel, Paul
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p. 1125 - 1128
(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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- Candida Rugosa lipase-catalyzed kinetic resolution of β-hydroxy- β-arylpropionates and δ-hydroxy-δ-aryl-β-oxo-pentanoates
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A simple and convenient method was reported for the preparation of optically active β-hydroxy-β-arylpropionates, δ-hydroxy-δ- aryl-β-oxo-pentanoates and their butyryl derivatives via CRL-catalyzed hydrolysis. The optically active products are potential precursors of some chiral pharmaceuticals and natural products.
- Xu, Chengfu,Yuan, Chengye
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p. 2169 - 2186
(2007/10/03)
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- Versatile one-step one-pot direct aldol condensation promoted by MgI 2
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A true one-step one-pot aldol-reaction procedure has been developed for the synthesis of β-hydroxy ketones and esters. The reaction can be run at room temperature by simply mixing four components in CH2Cl2, with medium-to-high yields of aldol products obtained after regular workup. Mechanistically, the process probably proceeds via Mg-enolate formation of the ketone or ester component, followed by addition to the electrophilic aldehyde.
- Wei, Han-Xun,Li, Kunyu,Zhang, Qian,Jasoni, Richard L.,Hu, Jiali,Pare, Paul W.
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p. 2354 - 2358
(2007/10/03)
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- Preparation of β-hydroxyesters from isoxazolines. A selective Ni 0bpy-catalyzed electrochemical method
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An electrocatalytic method for the reductive N-O cleavage of isoxazolines is described. Ni0bpy, generated in situ, was used to promote selective ring opening of 3-methoxy-5-phenylisoxazoline (1a) and 3-methoxy-[4,5]cyclohexylisoxazoline (1b). DMF and NaI were used as solvent and supporting electrolyte, and β-hydroxyesters 2a and 2b were obtained in high yields respectively, after acid hydrolysis. β-Hydroxynitriles 3a and 3b were also identified as side products.
- Caetano, Viviane F.,Demnitz, F.W. Joachim,Diniz, Flamarion B.,Mariz Jr., Ronaldo M.,Navarro, Marcelo
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p. 8217 - 8220
(2007/10/03)
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- Sodium borohydride reduction and selective transesterification of β-keto esters in a one-pot reaction under mild conditions
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An efficient and simple one-pot method of preparing β-hydroxy esters by sodium borohydride reduction cum selective transesterification of β-keto esters under mild conditions is described.
- Padhi, Santosh Kumar,Chadha, Anju
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p. 639 - 642
(2007/10/03)
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- Direct Zn-diamine promoted reduction of C=O and C=N bonds by polymethylhydrosiloxane in methanol
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Ketones and imines are chemoselectively reduced at room temperature in methanol to the corresponding alcohols and amines in high yields in a one-step procedure using polymethylhydrosiloxane (PMHS) and a simple zinc-diamine catalyst.
- Bette, Virginie,Mortreux, Andre,Lehmann, Christian W.,Carpentier, Jean-Francois
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p. 332 - 333
(2007/10/03)
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- PREPARATION OF ORGANOZINC HALIDES FROM REACTIVE HALOGEN COMPOUNDS AND THEIR USE
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A process for preparing organozinc halides in solvents, includes reacting a reactive halogen compound with zinc in one or more carboxylic esters. It is also possible to prepare keto, hydroxyl and amino compounds of organozinc halides obtained in a first step from a reactive halogen compound and zinc in one or more carboxylic esters, wherein the organozinc halide obtained is reacted in a second step with an electrophilic reaction partner and the reaction product of the second step is hydrolyzed in a third step.
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- Facile reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by an aqueous TiCl3/NH3 system: Selectivity and scope
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A simple and rapid procedure for the almost quantitative reduction of aromatic aldehydes, ketones, diketones and oxo aldehydes to alcohols by use of TiCl3/NH3 in aqueous methanol solution is reported. The reducing system distinguishes between different classes of aldehydes and/or ketones, and many functionalities that usually do not survive under reducing conditions are tolerated well. The concept of reversal of chemoselectivity has also been developed. A mechanism based on two sequential one-electron transfers from TiIII to the carbonyl carbon atom is proposed, the second SET becoming operative only in the presence of ammonium ion (either added or formed in situ). Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Clerici, Angelo,Pastori, Nadia,Porta, Ombretta
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p. 3326 - 3335
(2007/10/03)
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- Process for the preparation of hydroxy and amino compounds
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A process for the preparation of hydroxy and amino compounds, in which, in a first step, an aldehyde, ketone or imine is reacted in a Reformatsky reaction with a reactive halogen compound and zinc, in carboxylic esters as solvents, the reactive halogen compound being brought into contact with the zinc at the same time as or after contact with the aldehyde, ketone or imine, and in a second step, the reaction product of the first step is hydrolyzed.
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- Oxidation of benzylsilanes and benzyltins by oxovanadium(V) compound and molecular oxygen
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Benzylsilane and benzyltin compounds were oxidized by oxovanadium(V) compound under an oxygen atmosphere to afford the corresponding aromatic aldehydes (ketones) and/or carboxylic acids. In the reaction of benzyltins, oxovanadium(V) compound can be reduce
- Hirao, Toshikazu,Morimoto, Chihiro,Takada, Takashi,Sakurai, Hidehiro
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p. 5073 - 5079
(2007/10/03)
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- Optically active diphosphine compound, production intermediate thereof, transition metal complex containing the compound as ligand and asymmetric hydrogenation catalyst containing the complex
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This invention provides a novel diphosphine compound which is useful as a ligand of catalysts for asymmetric synthesis reactions, particularly asymmetric hydrogenation reaction. Particularly, it provides a diphosphine compound represented by a general formula (1): wherein R1and R2each independently represents a cycloalkyl group, an unsubstituted or substituted phenyl group or a five-membered aromatic heterocycle residue.
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- Addition of α-halocarboxylic acid esters to para-substituted benzaldehydes in the presence of pentacarbonyliron
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Pentacarbonyliron promotes addition of α-halocarboxylic acid esters at the carbonyl group of benzaldehyde and its para-substituted analogs. The substituent in the benzene ring strongly affects the process.
- Terent'ev,Vasil'eva,Kuz'mina,Mysova,Chakhovskaya
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p. 1273 - 1275
(2007/10/03)
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- Addition of halogenoacetic esters to aldehydes and ketones in the presence of Fe(CO)5
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The use of complex-forming solvents and variations in the reaction temperature made it possible to prepare α-halogeno β-hydroxy carboxylic esters upon addition of halogenoacetic esters to aldehydes and ketones promoted by iron pentacarbonyl.
- Terentiev,Vasilieva,Kuz'mina,Chakhovskaya,Brodsky,Belokon'
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p. 722 - 723
(2007/10/03)
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- A general method for the formation of zinc enolate equivalents from iodoacetates by diisopropylzinc-iodine exchange reaction: Preparation of β-Hydroxy esters
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Diisopropylzinc is found to be a highly efficient reagent for the formation of zinc enolate equivalents from various iodoacetates via iodine-Zinc exchange reaction at room temperature, affording β-Hydroxy esters in high yields by the reaction with aldehydes and ketones.
- Sato,Takizawa,Soai
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p. 2825 - 2826
(2007/10/03)
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- Conjugate addition of lithium enolates to aromatic carbonyl compounds complexed with aluminum tris(2, 6-diphenylphenoxide) (ATPH)
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Various lithium enolates of esters undergo effective 1, 6-addition to aromatic carbonyl compounds in the presence of aluminum tris(2, 6-diphenylphenoxide)(ATPH). Thieme.
- Saito, Susumu
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- Stereocontrol in organic synthesis using silicon-containing compounds. A formal synthesis of prostaglandins controlling the stereochemistry at C-15 using a silyl-to-hydroxy conversion following a stereochemically convergent synthesis of an allylsilane
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Hydrosilylation of isoprene with chloro(diphenyl)silane gave (Z)-chloro(2-methylbut-2-enyl)-diphenylsilane 7. The cuprate reagent derived from this chloride underwent conjugate addition to methyl cinnamate 11, 1,2-silylcupration with hex-1-yne 16 and allene 18, and allylic displacement reactions with 1-vinylcyclohexyl acetate 20 and (Z)-1-cyclopentyloct-2-en-1-yl acetate 22. The silyl group in each of the products was converted into a hydroxy, with the removal of the 2-methylbut-2-enyl group taking place under much milder acidic conditions than those needed to remove the phenyl group from the dimethyl(phenyl)silyl group, and making this group suitable for the conversion of an allylsilane into an allyl alcohol. A stereospecifically anti conjugate displacement of the allylic benzoate group in (Z)-(1S,5R,6R,7R,1′S)-7-benzoyloxy-6-(1′-benzoyloxyoct-2′- enyl)-2-oxabicyclo[3.3.0]octan-3-one 52, and a stereospecifically syn conjugate displacement of the carbamate group in (Z)-(1S,5R,6R,7R,1′R)-7-benzoyloxy-6-(1′-N-phenylcarbamoyloxyoct- 2′-enyl)-2-oxabicyclo[3.3.0]octan-3-one 51, gave stereo-convergently the same allylsilane (1′ E,2″Z)-(1S,5S,6R,7R,3′S)-7-benzoyloxy-6-[3′-(2″- methylbut-2″-enyl)-diphenylsilyloct-1′-enyl]-2-oxabicyclo[3.3.0] octan-3-one 53. Silyl-to-hydroxy conversion gave the allyl alcohol (E)-(1S,5S,6R,7R,3′S)-7-benzoyloxy-6-(3′-hydroxyoct-1′-enyl)- 2-oxabicyclo[3.3.0]octan-3-one 54, having the relative and absolute stereochemistry at C-15 of the prostaglandins.
- Fleming, Ian,Winter, Stephen B. D.
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p. 2687 - 2700
(2007/10/03)
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- Indium mediated reactions in water: Synthesis of β-hydroxyl esters
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A variety of β-hydroxyl esters were synthesized efficiently through indium mediated carbon-carbon bond formation in water followed by ozonolysis.
- Yi, Xiang-Hui,Meng, Yue,Li, Chao-Jun
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p. 4731 - 4734
(2007/10/03)
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- Reformatsky Reaction in Water: Evidence for a Radical Chain Process
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The Reformatsky reaction of 2-bromo esters and carbonyl compounds in the presence of zinc can be carried out in concentrated aqueous salt solutions without any cosolvent. The reaction of bromoacetates is greatly enhanced by catalytic amounts of benzoyl peroxide or peracids and gives satisfactory yields with aromatic aldehydes. Preparative yields comparable to those of the traditional procedure are obtained with ethyl 2-bromoisobutyrate. This ester needs no catalyst and reacts even with saturated aldehydes and aromatic ketones, although in low yields. A radical chain mechanism, initiated by electron abstraction from the organometallic Reformatsky reagent, is proposed. Two nonchain pathways, involving radicals directly produced on the metal surface, may compete, especially in the case of secondary and tertiary halides.
- Bieber, Lothar W.,Malvestiti, Ivani,Storch, Elisabeth C.
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p. 9061 - 9064
(2007/10/03)
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- Chemo- and Regioselective Reductions of Functionalized Epoxides by Bu3SnH/Bu3SnI-Phosphine Oxide
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A novel reagent, Bu3SnH/Bu3SnI-phosphine oxide, reduced functionalized epoxides to the corresponding alcohols in high chemo- and regioselectivities.
- Kawakami, Takayo,Tanizawa, Daisuke,Shibata, Ikuya,Baba, Akio
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p. 9357 - 9360
(2007/10/02)
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- Direct NMR assay of the enantiomeric purity of chiral β-hydroxy esters by using quinine as chiral solvating agent
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The use of quinine as a chiral solvating agent for NMR spectroscopy affords a general method for the enantiomeric purity determination of β-hydroxyesters. The ester group represents the most suitable probe for the measurements, which can be optimized by varying the molar ratio ester/quinine, the total concentration or the temperature.
- Uccello-Barretta,Pini,Mastantuono,Salvadori
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p. 1965 - 1972
(2007/10/03)
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- A cobalt-phosphine complex as mediator in the formation of carbon-carbon bonds
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The tetrakis(trimethylphospine)cobalt(0) complex, [Co{P(CH3)3}4], in either stoichiometric or catalytic amounts, was shown to be an efficient mediator for a one-pot Reformatsky-type reaction between activated halogen derivatives (esters, amides, lactones) and carbonyl compounds (aldehydes, ketones) to produce a variety of alcohols.
- Orsini,Pelizzoni,Pulici
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- The 2-methylbut-2-enyl(diphenyl)silyl group: A silyl group easily converted to hydroxyl in the presence of a 1,2-disubstituted C=C double bond
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The 2-methylbut-2-enyl(diphenyl)silyl group can be introduced into a variety of organic structures by way of the cuprate reagent 4, and it can then be converted into a hydroxyl group, even in the presence of a C=C double bond, unlike the dimethyl(phenyl)silyl group.
- Fleming, Ian,Winter, Stephen B. D.
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p. 7287 - 7290
(2007/10/02)
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