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Zhang Qiang - - 2010
An efficient and facile gold-catalyzed three-component tandem process for the assembly of two types of highly functionalized butenolides has been developed. In this reaction system, more than four chemical bonds are formed by a single gold catalyst. The present tandem protocol includes a direct coupling of alkynes, amines, and glyoxylic ...
Micskei Károly - - 2010
Amino acids are attractive sources of chirality in stoichiometric or catalytic transition metal/organic chemistry. In spite of easy availability and other advantages, the application of these ligands is hindered by several problems. Now, at the dawn of emerging D-amino acid biochemistry, efforts in this direction are becoming increasingly important. The ...
Fernandez Christian - - 2010
The isomerization of o-xylene, a prototypical example of shape-selective catalysis by zeolites, was investigated on hierarchical porous ZSM-5. Extensive intracrystalline mesoporosity in ZSM-5 was introduced by controlled silicon leaching with NaOH. In addition to the development of secondary porosity, the treatment also induced substantial aluminum redistribution, increasing the density of ...
Boyd R N - - 2010
A mechanism for creating amino acid enantiomerism that always selects the same large-scale chirality is identified, and subsequent chemical replication and galactic mixing that would populate the Galaxy with the predominant species is described. This involves (1) the spin of the 14N in the amino acids, or in precursor molecules ...
Panayotov Dimitar A - - 2010
Infrared spectroscopy of adsorbed CO has been used to characterize the effect of adsorbed methanol on the Lewis acidity of 4 nm rutile TiO(2) nanoparticles. Measurements of CO absorbance and vibrational frequency have revealed that CO adsorbs primarily at one class of Lewis acid sites on clean TiO(2) particles, where ...
Ren Qun - - 2010
The growing awareness of the importance of chirality in conjunction with biological activity has led to an increasing demand for efficient methods for the industrial synthesis of enantiomerically pure compounds. Polyhydroxyalkanotes (PHAs) are a family of polyesters consisting of over 140 chiral R-hydroxycarboxylic acids (R-HAs), representing a promising source for ...
Macklin Todd K - - 2010
Skipped polyenes (that is, 1,4-dienes and higher homologues) are stereodefined components of a vast array of biologically important natural products, including polyunsaturated fatty acids. Although widespread in nature, these architectures are generally considered to represent significant barriers to efficient chemical synthesis. Partial reduction of skipped poly-ynes provides a pathway to ...
Matsuo Jun-Ichi - - 2010
Ketones and acyl silanes were reduced to the corresponding alcohols by a simple procedure employing anti-1,3-diol and a catalytic amount (5 mol %) of 2,4-dinitrobenzenesulfonic acid in benzene at reflux. Asymmetric induction reached up to >99% ee when a chiral pentane-2,4-diol of 97% ee was used.
Belaud-Rotureau Mickaël - - 2010
Substitution of the fluoro or methoxy group in unprotected 2-fluoro- and 2-methoxybenzoic acids to afford N-aryl and N-alkyl anthranilic acids occurs upon reaction with lithioamides under mild conditions in the absence of a metal catalyst.
Zhao Haibo - - 2010
A simple copper-catalyzed direct amination of ortho-functionalized haloarenes (2-halobenzoic acid, 2-halobenzamide, and N-(2-bromophenyl)acetamide derivatives) has been developed with use of NaN(3) as the amino source in ethanol, and the corresponding ortho-functionalized aromatic amines were synthesized in good to excellent yields. The protocol undergoes one-pot Ullmann-type coupling of ortho-functionalized haloarenes with ...
Zeng Xiaofei - - 2010
A clean and highly efficient enantioselective addition of alpha-isocyanoacetamides to aliphatic aldehydes catalyzed by chiral phosphoric acid in the presence of MS 5 A in toluene at -40 degrees C was developed. Excellent yields (85-98%) and good to excellent enantioselectivities (up to >99% ee) were achieved.
Yu Jin-Di - - 2010
We have developed a regiospecific and highly stereoselective strategy for constructing the five-/six-membered monocyclic and bicyclic nitrogen heterocycle skeletons using PhSe group transfer radical cyclization of alpha-phenylseleno amido esters promoted by a Lewis acid (e.g., Yb(OTf)(3)) under UV irradiation. We obtained 5-/6-exo-trig mode cyclization products for the N-allyl/homoallyl substrates, whereas ...
Chen De-Jun - - 2010
A non-intermetallic PtPb/C catalyst of hollow structure is synthesized through a simple reduction method, and exhibits an activity as high as 3.6 times that of commercial Pd black and a much higher stability for electrooxidation of formic acid.
Feng Chao - - 2010
A highly efficient and mild palladium-catalyzed decarboxylative cross-coupling of aryl boronic acids and alkynyl carboxylic acids for the synthesis of unsymmetrical substituted alkynes is described for the first time.
Kitano Masaaki - - 2010
Protonated titanate nanotubes are demonstrated to function as a highly active solid Lewis acid catalyst even near room temperature. The high catalytic activity for the reaction can be attributed to the unique nanotube structure, which contains both Brønsted and Lewis acid sites.
Yoshida Masanori - - 2010
Enantioselective Michael addition of aldehydes to nitroalkenes was successfully carried out by asymmetric catalysis with L-phenylalanine lithium salt, giving gamma-nitroaldehydes in good yields with high enantioselectivity.
Ray Devalina - - 2010
Aryl and alkenyl amino acid derivatives were synthesized by a palladium catalyzed 1,4 addition of the corresponding boronic acids to 2-acetamidoacrylate.
Forsman Jonas J - - 2010
The fibrous polymer-supported sulfonic acid catalyst Smopex-101 H+ proved to be an efficient catalyst for the preparation of O-isopropylidene derivatives from a series of rare sugars. Acetonation of the reducing sugars L-arabinose, L-ribose, L-xylose, L-fucose, and L-rhamnose in N,N-dimethylformamide by 2,2-dimethoxypropane or 2-methoxypropene led to the formation of the kinetically ...
Felten Albert E - - 2010
Metal complexes of picolinaldehyde are identified as low-cost and environmentally benign catalysts, providing high reaction rates and turnovers for the racemization of amino acids. These pyridoxal surrogates demonstrate activity toward a variety of amino acid esters. Applications to chemoenzymatic dynamic kinetic resolutions provide access to amino acids in high yields ...
Benhaim Cyril - - 2010
We report herein the three-step enantioselective synthesis of beta-trifluoromethyl alpha-amino acids including trifluorovaline (TFV) using stereoselective hydrogenation with [((R)-trichickenfootphos)Rh(cod)]BF(4) catalyst as the key step.
Li Guilong - - 2010
Dihydropyran derivatives readily undergo addition to N-acyl imines in the presence of chiral phosphoric acids. This addition process yields an attractive product that is capable of a tandem oxidative-cyclization via an epoxide intermediate.
Zhu Ye - - 2010
Acidities of iridium hydride intermediates were shown to be critical in some transformations mediated by the chiral analogues of Crabtree's catalyst, 1-3. To do this, several experiments were undertaken to investigate the acidities of hydrogenation mixtures formed using these iridium-oxazoline complexes. DFT calculations indicated that the acidity difference for Ir-H ...
Tanaka Shinji - - 2010
A SH-selective allylation method using [CpRu(2-quinolinecarboxylato)(eta(3)-C(3)H(5))]PF(6) has been realized in various solvents including aqueous media to give allyl sulfides and allyl S-thioates, demonstrating the potential applicability to lipopeptide chemistry.
Liu Xiao - - 2010
(R)-(+)-Binol-functionalized chiral periodic mesoporous organosilicas (PMOs) with different framework compositions were successfully synthesized by cocondensation of (R)-2,2'-di(methoxymethyl)oxy-6,6'-di(1-propyltrimethoxysilyl)-1,1'-binaphthyl (BSBinol) with 1,2-bis(trimethoxysilyl)ethane (BTME) and tetramethoxysilane (TMOS) using triblock copolymer P123 as a template in acidic solution. The mixture of BTME and BSBinol can result in a highly ordered mesostructure in an acidic ...
Bagley Mark C - - 2010
Cyclodehydration of Bohlmann-Rahtz aminodienone intermediates using N-iodosuccinimide as a Lewis acid proceeds at low temperature under very mild conditions to give the corresponding 2,3,6-trisubstituted pyridines in high yield and with total regiocontrol.
Holm Martin Spangsberg - - 2010
Presently, very few compounds of commercial interest are directly accessible from carbohydrates by using nonfermentive approaches. We describe here a catalytic process for the direct formation of methyl lactate from common sugars. Lewis acidic zeotypes, such as Sn-Beta, catalyze the conversion of mono- and disaccharides that are dissolved in methanol ...
Samanta Krishnananda - - 2010
A new series of enantiomerically pure 2,3,4,4a,5,6-hexahydro-1H-pyrazino[1,2-a]quinoxalines were synthesized for the first time in twelve steps from 1-fluoro-2-nitrobenzene and S-amino acids with 13-20% overall yields. First use of intramolecular Mitsunobu cyclization for 1,2,3,4-tetrahydroquinoxalines followed by PPh(3)/I(2)/imidazole mediated 6-exo-tet cyclization were the key steps.
Fukuhara Gaku - - 2010
Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid and its alkali metal salts performed in a chiral ionic liquid gave chiral cyclodimers in good enantiomeric excesses of up to 41%, which is the highest ever reported for a photochirogenic reaction in chiral media.
Yazaki Ryo - - 2010
We report that a hard Lewis base substantially affects the reaction efficiency of direct catalytic asymmetric gamma-addition of allyl cyanide (1a) to ketones promoted by a soft Lewis acid/hard Brønsted base catalyst. Mechanistic studies have revealed that Cu/(R,R)-Ph-BPE and Li(OC(6)H(4)-p-OMe) serve as a soft Lewis acid and a hard Brønsted ...
Cardinal-David Benoit - - 2010
A new approach that takes advantage of N-heterocyclic carbene/Lewis acid cooperative catalysis provides access to cis-1,3,4-trisubstituted cyclopentenes from enals and chalcone derivatives with high levels of diastereoselectivity and enantioselectivity. The presence of Ti(OiPr)(4) as the Lewis acid allows for efficient substrate preorganization, which translates into high levels of diastereoselectivity. Additionally, ...
Gallo Jean Marcel R - - 2010
In this work, [Al]-SBA-15 samples were prepared by three different direct synthesis methods and one postsynthesis procedure, aiming to study the influence of the preparation procedures on their structural, textural, and physicochemical features. To this aim, samples were investigated by combining different experimental techniques (XRD, N(2) physisorption, (27)Al-MAS NMR, and ...
Sakee Uthai - - 2010
A straightforward route to a C-galactopyranosyl-linked 1,2-ethylenediamine is described. The five-step synthetic procedure involves: (i) C-allenylation of D-galactopyranose pentaacetate with propargyl trimethylsilane in the presence of a Lewis acid, (ii) iodination of allenyl galactopyranosyl tetraacetate to diiodoallyl galactopyranosyl tetraacetate, (iii) displacement of the allylic iodide with N-Boc-ethylenediamine, (iv) catalytic hydrogenation ...
Geboers Jan - - 2010
A combination of heteropolyacids and Ru on carbon catalyzes the conversion of concentrated cellulose feeds into hexitols under H(2) pressure. Quantitative conversion of ball-milled cellulose was observed with remarkable hexitol volume productivity.
Martin Connor L - - 2010
Development of efficient sequences for the total syntheses of (+/-)-actinophyllic acid (rac-1) and (-)-actinophyllic acid (1) are described. The central step in these syntheses is the aza-Cope/Mannich reaction, which constructs the previously unknown hexacyclic ring system of actinophyllic acid in one step from much simpler tetracyclic precursors. The tetracyclic hexahydro-1,5-methano-1H-azocino[4,3-b]indole ...
Ding Shilei - - 2010
Fine control of the self-assembly of silicon species to hierachical materials has attracted research attention for many years. The mesostructures produced by such processes under weak acidic-basic conditions mimic bioenvironments are the focus of current research. In this study, mesoporous silicas with various novel morphologies such as mesoporous spheres, nanotubes, ...
Prakash G K Surya - - 2010
Indanones and coumarins are important intermediates for the convenient synthesis of many pharmaceutical and biologically active compounds. Fluoroorganics play a vital role in the design of very effective therapeutics due to significant enhancenment in their lipophilicity, bioavailability, and fast uptake by the presence of fluorine in these molecules. Herein, we ...
Cox Daniel J - - 2010
The use of a chiral Br?nsted acid catalyst for the activation of trichloroacetimidate glycosyl donors has been demonstrated for the first time. In toluene the chirality of the acid catalyst is seen to influence the stereochemical outcome of the glycosylation processes, hinting that perhaps diastereocontrol of glycosylation processes may become ...
Xie Kai - - 2010
A Pd-catalyzed decarboxylative coupling of thiazoles and benzoxazole with various substituted benzoic acids is developed. The reaction is compatible with both electron-rich and electron-poor benzoic acids. It can also be extended to the synthesis of polyfluoro-substituted biaryls using polyfluorobenzenes as the starting materials.
Bénard Sébastien - - 2010
Reaction of anilines, primary and secondary aliphatic amines with cyclopropylboronic acid in dichloroethane in the presence of Cu(OAc)(2) (1 equiv.), 2,2'-bipyridine (1 equiv.) and sodium carbonate or sodium bicarbonate (2 equiv.) under air atmosphere afforded the corresponding N-cyclopropyl derivatives in good to excellent yields.
Azadi Pooya - - 2010
In this paper, a systematic study on preparation of multiwalled carbon nanotube (MWCNT)-supported nickel catalyst is pursued. Functional groups are introduced on the surface of MWCNTs using nitric acid, sulfuric acid, and partial oxidation in air. Nickel oxide nanoparticles are formed on the surface of functionalized multiwalled carbon nanotubes by ...
Veguillas Marcos - - 2010
Substituted 2-quinonyl boronic acids have been synthesised from 1,4-dimethoxy aromatic derivatives in two steps: regiocontrolled boronation and oxidative demethylation. The study of their dienophilic behaviour evidenced that the boron substituent significantly increases the reactivity and triggers an efficient domino process in which the Diels-Alder reaction was followed by a protodeboronation ...
Tong Xinli - - 2010
The dehydration of D-fructose and glucose has been studied with acidic ionic liquids as catalysts. A series of Brønsted-acidic ionic liquids has been synthesized and tested in the dehydration of D-fructose. The results showed that N-methyl-2-pyrrolidonium methyl sulfonate [NMP](+)[CH(3)SO(3)](-) and N-methyl-2-pyrrolidonium hydrogen sulfate [NMP](+)[HSO(4)](-) have high catalytic activity. Highly efficient ...
Johnston Jeffrey N - - 2010
A new means to activate diazoalkanes has been discovered and applied broadly over the past few years. Br?nsted acids, both achiral and chiral, have been used to promote the formation of carbon-carbon and carbon-heteroatom bonds with a growing number of diazoalkane derivatives. Aside from their straightforward ability to build structural ...
Wu Hong - - 2010
A mild, efficient, Cu(I)-catalyzed method for the conversion of arylboronic acids to aryl chlorides is reported. This method is particularly useful for the conversion of electron-deficient arylboronic acids to aryl chlorides, a transformation that is inefficient in the absence of Cu catalysis.
Lemire Alexandre - - 2010
Stereoselective syntheses of L-pipecolic acid and (2S,3S)-3-hydroxypipecolic acid were achieved from a chiral N-imino-2-phenyl-1,2-dihydropyridine intermediate. The 3-hydroxy substituent of the latter amino acid was introduced by hetero-Diels-Alder reaction of singlet oxygen with the 1,2-dihydropyridine.
Zagulyaeva Aleksandra A - - 2010
[Bis(trifluoroacetoxy)iodo]perfluoroalkanes C(n)F(2n+1)I(OCOCF(3))(2) (n = 4, 6, 8, 10, 12) can be conveniently prepared by the oxidation of the corresponding perfluoroalkyl iodides with Oxone in trifluoroacetic acid at room temperature and subsequently converted to the stable [hydroxy(tosyloxy)iodo]perfluoroalkanes, C(n)F(2n+1)I(OH)OTs, by treatment with p-toluenesulfonic acid. This general and convenient procedure has been further ...
Yamazaki Shigekazu - - 2010
An effective method for suppression of ring opening and rearrangement of acid-sensitive epoxides during methyltrioxorhenium(MTO)-catalyzed epoxidation of alkenes with H(2)O(2) by using 1-methylimidazole as a co-additive has been found. The combined use of 3-methylpyrazole and 1-methylimidazole as the additives has been found to be an effective procedure that affords excellent ...
Dumas Aaron M - - 2010
Meldrum's acid (2,2-dimethyl-1,3-dioxane-4,6-dione) is a molecule with a unique history, owing to its originally misassigned structure, as well as a unique place among acylating agents, owing to its high acidity and remarkable electrophilicity. In this Account, we outline the work of our group and others toward harnessing the reactivity of ...
Mallakpour Shadpour - - 2010
A number of chiral wholly aromatic polyesters (PEs) with phthalimido and flexible chiral unit in the backbone were prepared from a chiral synthesized diacid monomer, 5-(3-methyl-2-phthalimidylpentanoylamino)isophthalic acid (1), and various aromatic diols via the polyesterification reaction. The tosyl chloride/pyridine/N,N-dimethylformamide (DMF) system was used as a condensing agent. All of the ...
El Kadib Abdelkrim - - 2010
The beneficial effect of the bifunctional character of the chitosan@titania hybrid in heterogeneous catalysis was elucidated: considering a prototypical Henry condensation, Michael addition, and Jasminaldehyde synthesis, the cohabitation of a basic site (NH(2)) and an acidic site (Ti) in the same reactor provided clear activity and selectivity enhancements, with respect ...
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