- An improved synthesis of a polymer-supported distannane and its application to radical formation
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A polymer-supported distannane 1 was prepared by treatment of tin halide resin with lithium naphthalenide or sodium naphthalenide in THF. The content of the polymers 1 was determined to be 0.95 to 1.13 mmol/g tin as ditin. The polymer-supported distannane reagent was successfully applied to radical cyclizations of acyclic α-haloesters to yield γ-butyrolactones.
- Junggebauer, Joerg,Neumann, Wilhelm P.
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- SUPRAphos-based palladium catalysts for the kinetic resolution of racemic cyclohexenyl acetate
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High-throughput screening of the SUPRAphos library revealed a palladium catalyst based on supramolecular ligands that gave fast and highly efficient kinetic resolution of cyclohexenyl acetate with an S-value up to 12. The Royal Society of Chemistry.
- Jiang, Xiao-Bin,Van Leeuwen, Piet W. N. M.,Reek, Joost N. H.
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- PALLADIUM-CATALYZED ASYMMETRIC COUPLING REACTIONS BETWEEN ALLYLIC ACETATES AND ORGANOZINC REAGENTS. MECHANISTIC IMPLICATIONS
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Asymmetric induction and deuterium distribution studies have provided information about the mechanism of the palladium-catalyzed coupling reaction between allylic acetates and phenylzinc chloride, namely the presence of a symmetric η3-allylic ligand in the inetrmediate, probably along with a monodentate phosphine ligand.
- Fiaud, Jean-Claude,Aribi-Zouioueche, Louisa
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- A catalytic system for allylic acetoxylation consisting of palladium (II) and nitrate and using oxygen as final oxidant
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Cyclohexane is oxidized to cyclohexenyl acetate in 92% yield by 5 mol% palladium acetate and 5 mol% iron (III) nitrate in acetic acid under an atmosphere of oxygen. Addition of chloride or acetate are negative for the yield while addition of acetic anhydr
- Magnus Larsson,Akermark, Bjoern
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- Carbon-13 pulse Fourier transform NMR. Conformational preference of the hydroxyl and the acetoxyl group in 2-cyclohexenol and its acetate
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13C Fourier transform NMR spectra of cis and trans 5-t-butyl-2-cyclohexenols, 2-cyclohexenol and their acetates have been examined indicating that the pseudo-axial orientation of the hydroxyl and the acetoxyl group at the allylic position is fa
- Senda,Imaizumi
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- Palladium-catalyzed deracemization of allylic carbonates in water with formation of allylic alcohols: Hydrogen carbonate ion as nucleophile in the palladium-catalyzed allylic substitution and kinetic resolution
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The palladium-catalyzed deracemization of racemic cyclic and acyclic allylic methyl carbonates in water in the presence of N,N′-(1R,2R)-1,2-cyclohexanediylbis[2-(diphenylphophino)benzamide] proceeds with high enantioselectivities to give the corresponding allylic alcohols in high yields. This deracemization involves a palladium-catalyzed allylic substitution with the in-situ-formed hydrogen carbonate ion and an irreversible decomposition of the intermediate allylic hydrogen carbonates, with formation of the corresponding allylic alcohols. The palladium-catalyzed reaction of racemic cyclic allylic acetates with potassium hydrogen carbonate in water in the presence of the chiral bisphosphane proceeds with a highly selective kinetic resolution to give the corresponding allylic alcohols and allylic acetates. Copyright
- Luessem, Bernhard J.,Gais, Hans-Joachim
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- A further step to sustainable palladium catalyzed oxidation: Allylic oxidation of alkenes in green solvents
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The palladium catalyzed oxidation of alkenes with molecular oxygen is a synthetically important reaction which employs palladium catalysts in solution; therefore, a solvent plays a critical role for the process. In this study, we have tested several green solvents as a reaction medium for the allylic oxidation of a series of alkenes. Dimethylcarbonate, methyl isobutyl ketone, and propylene carbonate, solvents with impressive sustainability ranks and very scarcely exploited in palladium catalyzed oxidations, were proved to be excellent alternatives for the solvents conventionally employed in these processes, such as acetic acid. Palladium acetate alone or in the combination with p-benzoquinone efficiently operates as the catalyst for the oxidation of alkenes by dioxygen under 5–10 atm. For most substrates, the systems in green solvents showed better selectivity for allylic oxidation products as compared to pure acetic acid; moreover, the reactions in propylene carbonate solutions occurred even faster than in acetic acid.
- dos Santos Costa, Maíra,de Camargo Faria, Amanda,Mota, Rayssa L.V.,Gusevskaya, Elena V.
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- Discovery and Design of Family VIII Carboxylesterases as Highly Efficient Acyltransferases
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Promiscuous acyltransferase activity is the ability of certain hydrolases to preferentially catalyze acyl transfer over hydrolysis, even in bulk water. However, poor enantioselectivity, low transfer efficiency, significant product hydrolysis, and limited substrate scope represent considerable drawbacks for their application. By activity-based screening of several hydrolases, we identified the family VIII carboxylesterase, EstCE1, as an unprecedentedly efficient acyltransferase. EstCE1 catalyzes the irreversible amidation and carbamoylation of amines in water, which enabled the synthesis of the drug moclobemide from methyl 4-chlorobenzoate and 4-(2-aminoethyl)morpholine (ca. 20 % conversion). We solved the crystal structure of EstCE1 and detailed structure–function analysis revealed a three-amino acid motif important for promiscuous acyltransferase activity. Introducing this motif into an esterase without acetyltransferase activity transformed a “hydrolase” into an “acyltransferase”.
- Müller, Henrik,Godehard, Simon P.,Palm, Gottfried J.,Berndt, Leona,Badenhorst, Christoffel P. S.,Becker, Ann-Kristin,Lammers, Michael,Bornscheuer, Uwe T.
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supporting information
p. 2013 - 2017
(2020/11/30)
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- CHOLINE METABOLISM INHIBITORS
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The present disclosure relates to compounds, compositions and methods for inhibiting choline metabolism, e.g., conversion of choline to trimethylamine. Disclosed herein are compounds, compositions, and methods for inhibiting choline metabolism, e.g., conversion of choline to TMA. Also disclosed herein are compounds, methods and compositions for inhibiting choline metabolism by gut microbiota resulting in reduction in the formation of trimethylamine (TMA) and trimethylamine N-oxide (TMAO).
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Page/Page column 50; 102-103
(2020/07/05)
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- Carbamate-based P,O-ligands for asymmetric allylic alkylations
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Herein we report the design and successful catalytic application of modified Trost-ligands in asymmetric allylic alkylation (AAA) reactions. A small set of carbamate-monophosphine P,O-ligands has been prepared in a straightforward two-step synthetic procedure. After optimization of the reaction conditions, high catalytic activities and excellent enantioselectivity up to >99% have been attained.
- Pálv?lgyi, ádám Márk,Schnürch, Michael,Bica-Schr?der, Katharina
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- Ligand's electronegativity controls the sense of enantioselectivity in BIFOP-X palladium-catalyzed allylic alkylations
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Palladium-catalyzed allylic alkylations of sodium dimethyl malonate with 1,3-diphenylallyl acetate, employing BIFOP-H (biphenylbisfencholphosphite) and analogue (i.e. BIFOP-X, X = D, Cl, CN, N3) ligands, all yield (S)-enantiomeric products, while alkylations to cyclohexenyl acetate yield the (R)-enantiomeric C-C coupling product (up to 91% yield, 70% ee). The fluoro derivative BIFOP-F however, "switches" the sense of enantioselectivity, yielding the (R)-enantiomer for 1,3-diphenylallyl acetate and the (S)-enantiomer for the cyclohexenyl acetate (up to 92% yield, 67% ee). Computational analyses of transition structures (M06-2X-D3/def2-TZVP//B3LYP-D3(BJ)/def2-SVP) for these Pd-catalyzed allylic alkylations reproduce the experimental preference of BIFOP-H (and analogue BIFOP-X ligands) for (R)- or (S)-enantiomeric products of 1,3-diphenylallyl or cyclohexenyl acetate, respectively. The "F-switch" of the sense of enantioselectivity from BIFOP-H to BIFOP-F is also apparent computationally and is found (NBO-analyses) to originate from lp(Pd) → σ?(P-O) or lp(Pd) → σ?(P-F) hyperconjugations. The higher electronegativity of F vs. H in BIFOP-X hence controls the sense of enantioselectivity of this Pd-catalyzed allylic alkylation.
- Brüllingen, Eric,Neud?rfl, J?rg-Martin,Goldfuss, Bernd
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supporting information
p. 15743 - 15753
(2019/10/19)
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- The Allylic Acetoxylation of 1,1-Disubstituted Alkenes Catalyzed by a Palladium(II)/Monothiadiazole Ligand System
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A palladium(II)/monothiadiazole ligand catalytic system and its application in catalyzing the acetoxylation of 1,1-disubstituted alkenes have been developed. With this newly designed monothiadiazole thioether ligand, the reaction showed a broad scope with respect to 1,1-disubstituted olefins, giving the corresponding products in yields of 30-86percent.
- Jin, Can,Li, Xiaohan,Sun, Bin,Wang, Jiayang,Yang, Jin,Yu, Chuangming,Zhang, Xun,Zhuang, Xiaohui
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supporting information
p. 1479 - 1483
(2019/07/15)
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- Catalytic Electrophilic Alkylation of p-Quinones through a Redox Chain Reaction
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Allylation and benzylation of p-quinones was achieved through an unusual redox chain reaction. Mechanistic studies suggest that the existence of trace hydroquinone initiates a redox chain reaction that consists of a Lewis acid catalyzed Friedel–Crafts alkylation and a subsequent redox equilibrium that regenerates hydroquinone. The electrophiles could be various allylic and benzylic esters. The addition of Hantzsch ester as an initiator improves the efficiency of the reaction.
- Xu, Xiao-Long,Li, Zhi
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supporting information
p. 8196 - 8200
(2017/06/30)
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- Reusable and efficient polyvinylpolypyrrolidone-supported triflic acid catalyst for acylation of alcohols, phenols, amines, and thiols under solvent-free conditions
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Abstract: A triflic acid-functionalized polyvinylpolypyrrolidone was prepared and fully characterized by FT-IR, TGA, and SEM. This super acidic solid catalyst shows high catalytic activity for selective acylation of alcohols, phenols, amines, and thiols with anhydrides under solvent-free conditions at room temperature. In addition, this method features an easy to handle solid super acid catalyst and an operationally simple procedure, affording the desired acylated products in excellent yields. Graphical abstract: [Figure not available: see fulltext.].
- Tajbakhsh, Mahgol,Tajbakhsh, Mahmoud,Khaksar, Samad,Gazvini, Helia Janatian,Heidary, Marzieh
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p. 1117 - 1122
(2017/05/10)
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- Additive-free pd-catalyzed α-allylation of imine-containing heterocycles
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An additive-free Pd-catalyzed α-allylation of different imino-group-ontaining heterocycles is reported. The activation of α-CH pronucleophiles (pKa (DMSO) > 25) occurs without the addition of strong bases or Lewis acids using only the Pd/Xantphos catalyst system. The reaction scope has been studied for various 5- and 6-membered nitrogen-containing heterocycles (yields up to 96%). Mechanistic investigations suggest an initial allylation of the imine-N followed by a Pd-catalyzed formal aza-Claisen rearrangement.
- Kljajic, Marko,Puschnig, Johannes G.,Weber, Hansj?rg,Breinbauer, Rolf
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supporting information
p. 126 - 129
(2017/11/27)
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- Cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds
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A protocol for the cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds with carboxylic acids was developed in this work. Mechanistic studies revealed that C(sp3)–H bond activation in the hydrocarbon was the turnover-limiting step and the in-situ formed [Co(III)]Ot-Bu did not engage in hydrogen atom abstraction (HAA) of a C–H bond. This protocol was successfully incorporated into a synthetic pathway to β-damascenone that avoided the use of NBS.
- Ren, Tian-Lu,Xu, Bao-Hua,Mahmood, Sajid,Sun, Ming-Xue,Zhang, Suo-Jiang
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supporting information
p. 2943 - 2948
(2017/04/26)
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- The human carbonic anhydrase isoenzymes I and II inhibitory effects of some hydroperoxides, alcohols, and acetates
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The carbonic anhydrases (CAs, EC 4.2.1.1) represent a superfamily of widespread enzymes, which catalyze a crucial biochemical reaction, the reversible hydration of carbon dioxide to bicarbonate and protons. Human CA isoenzymes I and II (hCA I and hCA II) are ubiquitous cytosolic isoforms. In this study, a series of hydroperoxides, alcohols, and acetates were tested for the inhibition of the cytosolic hCA I and II isoenzymes. These compounds inhibited both hCA isozymes in the low nanomolar ranges. These compounds were good hCA I inhibitors (Ki s in the range of 24.93–97.99 nM) and hCA II inhibitors (Ki s in the range of 26.04–68.56 nM) compared to acetazolamide as CA inhibitor (Ki : 34.50 nM for hCA I and Ki : 28.93 nM for hCA II).
- Kose, Leyla Polat,Gulcin, ?lhami,Y?ld?r?m, Alper,Atmaca, Ufuk,?elik, Murat,Alwasel, Saleh H.,Supuran, Claudiu T.
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p. 1248 - 1253
(2016/10/09)
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- Exploring the reaction pathways of Pd(II)-catalyzed cyclohexene oxidation with molecular oxygen: Vinylic and allylic oxidation, disproportionation and oxidative dehydrogenation
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Palladium(ii) salts are able catalysts to promote different oxidative transformations of cyclohexene in the presence of molecular oxygen: vinylic and allylic oxidation and disproportionation. In this paper, we assessed the main aspects that govern these reactions, by using palladium salts (i.e. PdCl2, Pd(OAc)2, Pd(acac)2 and Pd(CF3COO)2) in protic solvents (i.e. CH3COOH and CH3OH). When carried out in CH3COOH solutions at 333 K, the Pd(ii)-catalyzed oxidation reactions preferentially convert cyclohexene to 2-cyclohexenil-1-acetate. Benzene was the secondary product. It was found that the efficiency of the palladium reoxidant followed the trend: Fe(NO3)3 > LiNO3 > CuCl2 > FeCl3. Pd(OAc)2 was the most active catalyst. Replacing Cu(OAc)2 by Fe(NO3)3 notably enhances the conversion of cyclohexene and the selectivity of 2-cyclohexenyl-1-acetate, reducing significantly the reaction time from 22 to 3 h. Conversely, when performed in CH3OH solutions, the reaction had its selectivity drastically changed; benzene and cyclohexane were the most selectively formed products (i.e. through disproportionation reaction). In this case, the reaction occurred at room temperature and in the absence of a reoxidant. Hence, Pd(CF3OO)2 is the most active and selective catalyst. The addition of the Fe(NO3)3 reoxidant and increasing the reaction temperature to 328 K resulted in the formation of 1,2-dimethoxycyclohexane and benzene as major products (i.e. allylic oxidation and oxidative dehydrogenation products, respectively). Catalytic cycles for these transformations were proposed based on experimental data and palladium chemistry.
- Da Silva,Berlini
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p. 7996 - 8005
(2016/09/12)
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- Allylic oxidation of alkenes catalyzed by a copper-aluminum mixed oxide
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A strategy for the allylic oxidation of cyclic alkenes with a copper-aluminum mixed oxide as catalyst is presented. The reaction involves the treatment of an alkene with a carboxylic acid employing tert-butyl hydroperoxide as the oxidant. In all cases, the corresponding allylic esters are obtained. When l-proline is employed, the allylic alcohol or ketone is obtained. The oxidation of cyclohexene and valencene has been optimized by design of experiments (DoE) statistical methodology.
- Garcia-Cabeza, Ana Leticia,Marin-Barrios, Ruben,Moreno-Dorado, F. Javier,Ortega, Maria J.,Massanet, Guillermo M.,Guerra, Francisco M.
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supporting information
p. 1598 - 1601
(2014/04/17)
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- Enzyme- and ruthenium-catalyzed dynamic kinetic resolution of functionalized cyclic allylic alcohols
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Enantioselective synthesis of functionalized cyclic allylic alcohols via dynamic kinetic resolution has been developed. Cyclopentadienylruthenium catalysts were used for the racemization, and lipase PS-IM or CALB was employed for the resolution. By optimization of the reaction conditions the formation of the enone byproduct was minimized, making it possible to prepare a range of optically active functionalized allylic alcohols in good yields and high ee's.
- Lihammar, Richard,Millet, Renaud,Baeckvall, Jan-E.
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p. 12114 - 12120
(2014/01/06)
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- Enzymatic preparation of (1S,2R)- and (1R,2S)-stereoisomers of 2-halocycloalkanols
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The stereoisomers of cis-2-halocycloalkanols were resolved by a kinetically controlled transesterification with vinyl acetate in the presence of lipases in organic media. High enantioselectivities (ee >98%) and good isolated yields were obtained for all substrates using the appropriate lipase. Burkholderia cepacia lipase was the most efficient enzyme for the resolution of these substrates. The enantiomeric purities of the compounds were defined by derivatization with Mosher's acid and the absolute configurations were determined by chemical correlation.
- Kolodiazhna, Olga O.,Kolodiazhna, Anastasy O.,Kolodiazhnyi, Oleg I.
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- Pentafluorophenylammonium triflate as a mild and new organocatalyst for acylation of alcohols, phenols, and amines under solvent-free condition
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A simple, inexpensive, environmentally friendly and efficient route for the acylation of a number of alcohols, phenols and amines using pentafluorophenylammonium triflate (PFPAT) as a catalyst is described. PFPAT organocatalyst is air-stable, cost-effective, easy to handle, and easily removed from the reaction mixtures.
- Khaksar, Samad,Zakeri, Hasan
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p. 576 - 579,4
(2020/08/31)
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- Highly enantioselective synthesis of 3-substituted furanones by palladium-catalyzed kinetic resolution of unsymmetrical allyl acetates
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Resolving the issue: A near-perfect Pd-catalyzed kinetic resolution of 1,3-disubstituted unsymmetrical allylic acetates uses silyl enol ethers as nucleophiles to access the important 3-substituted-furanone scaffold (see scheme; DACH=diaminocyclohexyl, dba=dibenzylideneacetone). The reaction proceeds under mild conditions and provides the desired products with excellent chemo-, regio-, and enantioselectivity. Copyright
- Mao, Bin,Ji, Yining,Fananas-Mastral, Martin,Caroli, Giuseppe,Meetsma, Auke,Feringa, Ben L.
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supporting information; experimental part
p. 3168 - 3173
(2012/05/05)
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- Enzymatic resolution of stereoisomers of 2-iodocyclohexanol
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All four optically active stereoisomers of 2-iodocyclohexanol were synthesized. Their enantiomeric purity was determined upon derivatization with Mosher's acid, absolute configuration have been established by chemical correlation.
- Kolodiazhna,Kolodiazhna,Kolodiazhnyi
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p. 2175 - 2177
(2013/10/01)
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- PROCESS FOR PRODUCING ESTER COMPOUND HAVING a,?-UNSATURATED BOND
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A process for producing an α,β-unsaturated bond-containing ester compound, comprising: reacting an internal olefin or a cyclic olefin having one carbon-carbon double bond or more at a position other than terminals of a molecule thereof (the internal olefin and the cyclic olefin may each contain a hetero atom) with a carboxylic acid in an amide-based solvent in the presence of a palladium catalyst, a base, and molecular oxygen, thereby bonding a carboxyl group of the carboxylic acid to at least one of carbon atoms constituting the carbon-carbon double bond and carbon atoms at allylic positions of the internal olefin or the cyclic olefin, to obtain an ester compound having an α,β-unsaturated bond, the amide-based solvent being represented by the following formula (1): (in the formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms; R2 and R3 each independently represent an alkyl group having 1 to 4 carbon atoms or an aryl group; and when R1 and R2 are alkyl groups, R1 and R2 may be bonded to each other to form a ring structure).
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Page/Page column 9
(2013/02/27)
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- Intermolecular amination of allyl alcohols with sulfamates: Effective utilization of mercuric catalyst
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Herein, we describe the intermolecular amination of allyl alcohols with sulfamates, which have been underutilized as nitrogen nucleophiles for allylic amination. Methyl sulfamate is a good nucleophile in the presence of mercuric triflate and efficiently generates monoallylation products in excellent yield at room temperature. Furthermore, the solid-supported mercuric catalyst silaphenyl mercuric triflate also showed remarkable catalytic activity for the allylic amination. Intermolecular amination of allyl alcohol with sulfamate as a modifiable nitrogen nucleophile is presented. Mercuric reagents act as highly efficient catalyst for the allylic amination, and the procedure was applied to the preparation of various amine derivatives. In many cases, the reaction can be carried out at room temperature and is applicable to a large range of allylic alcohols to give the monoallylated products in excellent yield. Copyright
- Yamamoto, Hirofumi,Ho, Elisabeth,Sasaki, Ikuo,Mitsutake, Mizuho,Takagi, Yuichi,Imagawa, Hiroshi,Nishizawa, Mugio
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supporting information; experimental part
p. 2417 - 2420
(2011/06/10)
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- InI3/me3sii-catalyzed direct alkylation of enol acetates using alkyl acetates or alkyl ethers
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A combined Lewis acid of InI3 and Me3SiI was used to catalyze the direct coupling reactions of enol acetates with alkyl acetates or alkyl ethers without generating metal waste. The easily-handled alkylating reagents enlarged the application area of this coupling reaction. 2011 The Chemical Society of Japan.
- Onishi, Yoshiharu,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 1223 - 1225
(2011/11/29)
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- A paradigm for solvent and temperature induced conformational changes
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The complex conformational dependency on environment of Boc-amine (see scheme) has been investigated. This model organic molecule has many features applicable to areas of chemistry, biology, physics, and computational chemistry. It is soluble in both non-polar and polar solvents, conformationally heterogeneous, and capable of supramolecular assembly. Copyright
- Shpasser, Dina,Balazs, Yael S.,Kapon, Moshe,Sheynis, Tania,Jelienk, Raz,Eisen, Moris S.
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supporting information; experimental part
p. 8285 - 8289
(2011/08/07)
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- Cobalt-catalyzed reductive allylation of alkyl halides with allylic acetates or carbonates
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An efficient method for the direct allylation of alkyl halides catalyzed by simple cobalt(II) bromide has been developed. This reaction, using a variety of substituted allylic acetates or carbonates, provides the linear product as the major product. It displays broad substrate scope and good functional group tolerance. Copyright
- Qian, Xin,Auffrant, Audrey,Felouat, Abdellah,Gosmini, Corinne
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supporting information; experimental part
p. 10402 - 10405
(2011/12/03)
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- NOVEL PHENYLAMINO ISONICOTINAMIDE COMPOUNDS
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The invention provides novel compounds according to Formula (I), their manufacture and use for the treatment of hyperproliferative diseases, such as cancer, restenosis and inflammation.(Formula I)
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Page/Page column 24
(2010/04/03)
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- Synthesis and characterization of oligonuclear Ru, Co and Cu oxidation catalysts
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In this work, we report the preparation and crystal structures of three new oligonuclear complexes, Ru2(bbpmp)(μ-OAc)3 (4), [Co2(bbpmp)(μ-OAc)(μ-OMe)](PF6) (5), [Cu 4(Hbbpmp)2(μ-OAc)(H2O)2](OAc)(PF 6)2 (6) {H3bbpmp = 2,6-bis[(2-hydroxybenzyl)- (2-pyridylmethyl)aminomethyl]-4-methyl-phenol (3)}. The structures of the complexes were determined by single-crystal X-ray diffraction. The oxidation states of ruthenium, cobalt and copper in the complexes are +3, +3 and +2, respectively. In 4 and 5, RuIII and CoIII are coordinated to four oxygen and two nitrogen atoms in an octahedral geometry, while in 6, CuII adopts both octahedral (CuN2O4) and square-pyramidal (CuN2O3) geometry. The potential of the three complexes as oxidation catalysts has been investigated. Copyright
- Lee, Bao-Lin,Kaerkaes, Markus D.,Johnston, Eric V.,Inge, Andrew K.,Tran, Lien-Hoa,Xu, Yunhua,Hansson, Oerjan,Zou, Xiaodong,Akermark, Bjoern
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experimental part
p. 5462 - 5470
(2011/03/01)
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- One-pot sequence for reductive-acetylation of carbonyl compounds with (N-methylimidazole)(tetrahydroborato)zinc complex
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Reductive-acetylation of variety of aliphatic and aromatic aldehydes and ketones, α,β-unsaturated carbonyl compounds are examined efficiently with (N-methylimidazole)(tetrahydroborato)zinc complex, [Zn(BH4) 2(nmi)], under mild condition in THF at room temperature or reflux conditions. The corresponding acetates were obtained in excellent yields (90-98 %).
- Setamdideh, Davood,Khezri, Behrooz
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experimental part
p. 5766 - 5772
(2012/07/28)
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- Mechanistic investigations of bipyrimidine-promoted palladium-catalyzed allylic acetoxylation of olefins
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Several pyridine-like ligands were found to improve Pd(OAc) 2-catalyzed allylic oxidation of allylbenzene to cinnamyl acetate by p-benzoquinone in acetic acid. The best ligand examined, bipyrimidine, was used to identify the catalyst precursor for this system, (bipyrimidine)Pd(OAc) 2, which was fully characterized. Mechanistic studies suggest the reaction takes place through disproportionation of (bipyrimidine)Pd(OAc) 2 to form a bipyrimidine-bridged dimer, which reacts with olefin to form a PdII-olefin adduct, followed by allylic C-H activation to produce (η3-allyl)PdII species. The (η3-allyl)PdII intermediate undergoes a reversible acetate attack to generate a Pd0-(allyl acetate) adduct, which subsequently reacts with p-benzoquinone to release allyl acetate and regenerate (bipyrimidine)Pd(OAc)2. No KIE is observed for the competition experiment between allylbenzene-d0 and allylbenzene-d5 (CD2=CDCD2C6H5), suggesting that allylic C-H activation is not rate-determining. Catalytic allylic acetoxylations of other terminal olefins as well as cyclohexene were also effected by (bipyrimidine)Pd(OAc)2.
- Lin, Bo-Lin,Labinger, Jay A.,Bercaw, John E.
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experimental part
p. 264 - 271
(2009/10/23)
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- Highly enantioselective and regioselective carbonyl reduction of cyclic α,β-unsaturated ketones using TarB-N02 and sodium borohydride
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Asymmetric 1,2-reduction of α,β-unsaturated ketones using TarB-NO2 and NaBH4 Is reported. Simple cycloalkenones give products In low enantiomeric excess. However, cycloalkenones with a-substituents, such as halides, alkyl, and aryl, have been enantioselectively reduced with this system to yield chiral allylic alcohols In enantiomeric excess up to 99%. The starting materials for TarB-N02 are inexpensive, and the boronlc acid can be easily recovered In high yield by a simple acid extraction.
- Kim, Jinsoo,Bruning, John,Park, Kevin E.,Lee, David J.,Singaram, Bakthan
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supporting information; experimental part
p. 4358 - 4361
(2009/12/24)
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- Catalytic allylic C-H acetoxylation and benzoyloxylation via suggested (η3-Allyl)palladium(IV) intermediates
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"Chemical Equation Presented" Palladium-catalyzed allylic acetoxylations and benzoyloxylations were carried out using iodonium salts. The reactions proceed under mild conditions with high reglo- and stereoselectivity. The catalysis can be performed under
- Pilarski, Lukasz T.,Selander, Nicklas,Boese, Dietrich,Szabo, Kalman J.
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supporting information; experimental part
p. 5518 - 5521
(2010/02/28)
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- Acyloxylactonisations mediated by lead tetracarboxylates
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The reaction of lead(IV) tetracarboxylates with carboxylic acids containing unsaturated side chains has been found to give acyloxy lactone products in a diastereoselective process; the reaction can be extended to lead(IV) tetrazolates to give the analogous outcome. Mechanistic implications of these results are discussed.
- Cottrell, Ian F.,Cowley, Andrew R.,Croft, Laura J.,Hymns, Lauren,Moloney, Mark G.,Nettleton, Ewan J.,Kirsty Smithies,Thompson, Amber L.
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body text
p. 2537 - 2550
(2009/08/07)
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- o-benzenedisulfonimide as a soft, efficient, and recyclable catalyst for the acylation of alcohols, phenols, and thiols under solvent-free conditions: Advantages and limitations
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o-Benzenedisulfonimide turns out to be a highly efficient Bransted acid catalyst for the acylation of a number of alcohols, phenols, and thiols under a metal- and solvent-free procedure; reaction conditions are mild and yields very good. After the workup, the catalyst can be easily recovered and purified, ready to be reused, with economic and ecological advantages. Georg Thieme Verlag Stuttgart · New York.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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experimental part
p. 3625 - 3632
(2009/07/04)
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- Copper triflate/t-BuOOAc-catalyzed amidation of allylic and benzylic acetates with sulfonamides
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A copper triflate/t-BuOOAc-catalyzed amidation of allylic and benzylic acetates has been developed which is suitable for the coupling of a wide variety of functionalized sulfonamide nucleophiles with acetate electrophiles. The methodology allows for the amidation of benzylic substrates which are not further activated by an additional adjacent alkene or alkyne, enabling simple allylic acetates and primary benzylic acetates to be used as reaction partners.
- Powell, David A.,Pelletier, Guillaume
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p. 2495 - 2498
(2008/09/19)
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- A nucleophilic Fe catalyst for transesterifications under neutral conditions
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Carboxylic esters belong to the most important functional groups in organic chemistry. Strong efforts have been made in developing mild catalytic procedures for their preparation. Among the various methods developed to date, transesterifications have occupied an important space. In the present paper, a new catalytic method for this process based on the use of nucleophilic Fe(-II) complexes is presented. Evidence for the formation of an intermediate acyl Fe complex will be presented as well as investigations on scope and limitations.
- Magens, Silja,Ertelt, Melanie,Jatsch, Anja,Plietker, Bernd
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- A highly stereoselective divergent synthesis of bicyclic models of photoreactive sesquiterpene lactones
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Sesquiterpene lactones are natural stereochemically pure compounds, which show a number of biological activities. In order to study the reactivity of sesquiterpene lactones in biological systems, we describe herein the asymmetric synthesis of a simple mod
- Fuchs, Sebastien,Berl, Valerie,Lepoittevin, Jean-Pierre
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p. 1145 - 1152
(2008/02/06)
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- Palladium catalytic species containing chiral phosphites: Towards a discrimination between molecular and colloidal catalysts
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Palladium nanoparticles (Pd1-Pd3) stabilized by chiral diphosphite ligands (1-3), were synthesized and tested as catalysts for the allylic alkylation reaction, using different substrates (rac-I, rac-III and rac-V). Carbohydrate ligands (1 and 2), only differing in the C-3 configuration, led to a remarkable difference in stability of the corresponding nanoparticles: while Pd1 is a robust catalyst, Pd2 decomposes into molecular species. In addition, the high enantioselective systems, Pd1 and Pd3, are only active for a substrate containing phenyl groups. Concerning the catalytic behaviour of the corresponding molecular systems, palladium complexes coordinated to ligands 1 or 3, gave excellent asymmetric inductions, but an analogous catalyst accommodating ligand 2, was not found selective.
- Favier, Isabelle,Gomez, Montserrat,Muller, Guillermo,Axet, M. Rosa,Castillon, Sergio,Claver, Carmen,Jansat, Susanna,Chaudret, Bruno,Philippot, Karine
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p. 2459 - 2469
(2008/09/19)
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- Sequential catalysis: A metathesis/dihydroxylation sequence
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(Chemical Equation Presented) A real step-saver: A single ruthenium-carbene complex catalyzes a sequence of two reactions, namely, a metathesis reaction (ring-closing or cross metathesis) and subsequent dihydroxylation of the newly formed double bond. A v
- Beligny, Samuel,Eibauer, Stefan,Maechling, Simon,Blechert, Siegfried
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p. 1900 - 1903
(2007/10/03)
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- Ruthenium-catalyzed tandem olefin metathesis-oxidations
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(Chemical Equation Presented) The utility of Grubbs' 2nd generation metathesis catalyst has been expanded by the development of two tandem olefin metathesis/oxidation protocols. These ruthenium-catalyzed processes provide cis-diols or α-hydroxy ketones from simple olefinic starting materials.
- Scholte, Andrew A.,Mi, Hyun An,Snapper, Marc L.
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p. 4759 - 4762
(2007/10/03)
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- Applications of 4,4′-Me3Si2-BINAP in transition-metal-catalyzed asymmetric carbon-carbon bond-forming reactions
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(Chemical Equation Presented) A recently developed BINAP derivative with trimethylsilyl substituents on the 4- and 4′-positions of the binaphthyl skeleton, 2,2′-bis-(diphenylphosphino)-4,4′-bis(trimethylsilyl)-1, 1′-binaphthyl (tms-BINAP), was used in a variety of transition-metal- catalyzed asymmetric carbon-carbon bond-forming reactions. In π-allylpalladium-mediated reactions, tms-BINAP gave better enantioselectivity than the unsubstituted BINAP, and the origin of the improved enantioselectivity was gained from an X-ray structural study of [Pd(η3-C 3H5)((R)-tms-BINAP)]ClO4.
- Ogasawara, Masamichi,Ngo, Helen L.,Sakamoto, Takeshi,Takahashi, Tamotsu,Lin, Wenbin
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p. 2881 - 2884
(2007/10/03)
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- Oxidative cyclizations in a nonpolar solvent using molecular oxygen and studies on the stereochemistry of oxypalladation
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Oxidative cyclizations of a variety of heteroatom nucleophiles onto unactivated olefins are catalyzed by palladium(II) and pyridine in the presence of molecular oxygen as the sole stoichiometric oxidant in a nonpolar solvent (toluene). Reactivity studies of a number of N-ligated palladium complexes show that chelating ligands slow the reaction. Nearly identical conditions are applicable to five different types of nucleophiles: phenols, primary alcohols, carboxylic acids, a vinylogous acid, and amides. Electronrich phenols are excellent substrates, and multiple olefin substitution patterns are tolerated. Primary alcohols undergo oxidative cyclization without significant oxidation to the aldehyde, a fact that illustrates the range of reactivity available from various Pd(II) salts under differing conditions. Alcohols can form both fused and spirocyclic ring systems, depending on the position of the olefin relative to the tethered alcohol; the same is true of the acid derivatives. The racemic conditions served as a platform for the development of an enantioselective reaction. Experiments with stereospecifically deuterated primary alcohol substrates rule out a "Wacker-type" mechanism involving anti oxypalladation and suggest that the reaction proceeds by syn oxypalladation for both mono- and bidentate ligands. In contrast, cyclizations of deuterium-labeled carboxylic acid substrates undergo anti oxypalladation.
- Trend, Raissa M.,Ramtohul, Yeeman K.,Stoltz, Brian M.
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p. 17778 - 17788
(2007/10/03)
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- Efficient palladium-catalyzed nucleophilic addition of triorganoindium reagents to carbocyclic derivatives
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Palladium (0)-catalyzed allylic substitution reactions employing triorganoindium reagents have been investigated. In situ generated vinyl- and arylindiums react with substituted and unsubstituted cyclohex-2-enyl esters in the presence of 1-3 mol % Pd2(dba)3 to produce vinyl- or arylcyclohexenes in moderate to excellent yields. The stereoselectivity of this process was also examined, and evidence is presented that the reaction proceeds with inversion of stereochemical configuration.
- Baker, Lucas,Minehan, Thomas
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p. 3957 - 3960
(2007/10/03)
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- Polymer-supported distannanes: A new and efficient synthesis of highly effective reagents for iodine atom transfer cyclisations
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Polymeric distannanes were synthesised by the cross-linking of polystyrene bound tin hydride functionalities using a palladium mediated dehydrogenative coupling. The polymers were characterised by spectroscopic methods (IR and 13C, 119/su
- Hernán, Alejandro G.,Kilburn, Jeremy D.
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p. 831 - 834
(2007/10/03)
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- Palladium-catalyzed enantioselective allylic alkylation of thiocarboxylate ions: Asymmetri synthesis of allylic thioesters and memory effect/dynamic kinetic resolution of allylic esters
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The palladium-catalyzed allylic alkylation of KSAc and KSBz with racemic cyclic and acyclic allylic esters by using N,N'-(1R,2R)-1,2-cyclohexandiylbis[2-(diphenylphosphino)-benzamide] as ligand frequently gave the corresponding allylic thioesters with high ee values and yields. The reaction of the cyclic allylic carbonates with KSAc in the presence of H20 was accompanied by a partial palladium-catalyzed enantioselective "hydrolysis" of the substrates with formation of the corresponding enantioenriched allylic alcohols. The degree of the "hydrolysis" was strongly dependent on the solvent and the thiocarboxylate ion. Highly selective kinetic resolutions (KRs) were observed in the palladium-catalyzed reaction of the racemic cyclohexenyl and cycloheptenyl acetates with KSAc. While the KR of the cyclohexenyl acetate is characterized by a selectivity factor S = 72 ± 19, that of the cycloheptenyl acetate afforded (R)-cycloheptenyl acetate of ≥ 99% ee in 48% yield and (S)-cycloheptenyl thioacetate of 98% ee in 50% yield. The palladium-catalyzed reaction of the racemic cyclopentenyl acetate with KSAc showed a strong "memory effect" (ME), that is, both enantiomers reacted with different enantioselectivities. The ME was probed by studying the palladium-catalyzed reactions of both the matched acetate of ≥ 99% ee and the mismatched acetate of ≥ 99% ee with KSAc. The acetates not only reacted with different enantioselectivities and rates but also suffered an unexpected and concomitant palladium-catalyzed racemization in the presence of the chiral ligand. This led in the case of the mismatched acetate to a temporary dynamic kinetic resolution (DKR) that featured a racemization of the mismatched acetate by the chiral catalyst. Studies of the palladium-catalyzed reaction of the racemic cyclopentenyl acetate, carbonate, and naphthoate with KSAc in the presence of the chiral ligand also showed the ME to be strongly dependent on the nucleofuge. This also allowed the synthesis of (S)-cyclopentenyl thioacetate of 92% ee in high yield from the racemic cyclopentenyl naphthoate.
- Luessem, Bernhard J.,Gais, Hans-Joachim
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p. 4041 - 4052
(2007/10/03)
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- Palladium-Catalyzed Equilibrium Addition of Acidic OH Groups across Dienes
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Mildly acidic O-H groups undergo transition-metal-catalyzed reversible addition across the C=C bonds of cyclic and acyclic dienes. For example, the simple complex [Pd(PPh3)4] (1 mol%) effectively catalyzes both the forward addition o
- Utsunomiya, Masaru,Kawatsura, Motoi,Hartwig, John F.
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p. 5865 - 5868
(2007/10/03)
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- Deoxygenative dimerization of benzylic and allylic alcohols, and their ethers and esters using lanthanum metal and chlorotrimethylsilane in the presence of a catalytic amount of iodine and copper(I) iodide
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Benzylic and allylic alcohols were deoxygenatively dimerized by a treatment with lanthanum metal and chlorotri-methylsilane in the presence of a catalytic amount of iodine, giving the corresponding coupling products, alkanes, in moderate-to-good yields. This dimerization reaction was dramatically accelerated by the addition of a catalytic amount of copper(I) iodide. Similarly, ethers and esters were deoxygenatively dimerized by La/Me3SiCl/cat.I2/cat.CuI system in the presence of a catalytic amount of H2O.
- Nishino, Toshiki,Nishiyama, Yutaka,Sonoda, Noboru
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p. 635 - 641
(2007/10/03)
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- Modular bis(oxazoline) ligands for palladium catalyzed allylic alkylation: Unprecedented conformational behaviour of a bis(oxazoline) palladium η3-1,3-diphenylallyl complex
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New families of enantiopure bis(oxazolines) with 4,5-trans (5a - g) or 4,5-cis (6c) stereochemistry at the individual rings have been prepared in high yield. Their η3-allyl palladium complexes (8a-g, 9c and 10) have been used as catalytic precu
- Pericas, Miquel Angel,Puigjaner, Cristina,Riera, Antoni,Vidal-Ferran, Anton,Gomez, Montserrat,Jimenez Sr., Francisco,Muller, Guillermo,Rocamora, Merce
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p. 4164 - 4178
(2007/10/03)
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- Synthesis of allylic esters and ethers using polymer-supported selenium bromidet
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The treatment of adducts from polymer-supported selenium bromide on olefins with anhydrous carboxylate or alcohol and oxidation of the resulting products afford allylic esters and ethers in good yield and purity.
- Sheng, Shou-Ri,Huang, Xian
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p. 184 - 185
(2007/10/03)
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- An air oxidizable bimetallic palladium(II) catalyst for asymmetric allylic oxidation of olefins in acetic acid
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A bimetallic palladium(II) complex containing a triketone ligand and a bridging diphosphine ligand oxidizes olefins in acetic acid to allylic acetates by a direct air oxidation, which does not require intermediate redox systems. When the diphosphine is chiral, an asymmetric reaction occurs which gives enantioselectivities between 52 and 78% for cyclic olefins.
- El-Qisiari, Arab K.,Qaseer, Hanan A.,Henry, Patrick M.
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p. 4229 - 4231
(2007/10/03)
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- Vinylic, allylic and homoallylic oxidations of alkenes via π- and σ-organopalladium complexes
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The stoichiometric and catalytic pathways of oxidative esterification of alkenes via intermediate organopalladium complexes are discussed. The oxidation of propylene, hex-1-ene and cyclohexene by PdII acido complexes containing achiral, racemic and chiral carboxylate ligands was first studied in a series of solvents other than acetic acid. Significant changes in the selectivity of the PdII-promoted reaction with changes in the solvent nature and ligand chirality were observed. A way to allylic esters based on low-valence Pd nanoclusters provide highly selective oxidation of acyclic alkenes into allylic esters, whereas cycloalkenes undergo mostly redox disproportionation. The role of π-alkene, σ-alkenyl and π-allyl complexes in the mechanism of the alkene oxidative esterification with PdII complexes and low-valence Pd clusters is discussed.
- Kozitsyna, N.Yu.,Vargaftik,Moiseev
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p. 274 - 291
(2007/10/03)
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