- Selectivity engineering of phase transfer catalyzed alkylation of 2′-hydroxyacetophenone: Enhancement in rates and selectivity by creation of a third liquid phase
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Enhancements in rate of reaction and selectivity of the desired product in biphasic reactions are achieved by creating a third liquid phase, under appropriate conditions, where the third liquid phase is the locale of the main reaction, having a dramatic effect on product distribution in complex chemical reactions. Thus, in the case of phase transfer catalysis (PTC), conversion of liquid-liquid (L-L) PTC into liquid-liquid-liquid (L-L-L) PTC is of considerable techno-commercial interest resulting in waste minimization which is a major theme of green chemistry. Etherification of 2′-hydroxyacetophenone with 1-bromopentane, under traditional liquid-liquid phase transfer catalysis, results in loss of catalyst. However, the transformation of two liquid phases into three liquid phases (L-L-L) PTC leads enhancement in rates by orders of magnitude, with 100% conversion of the limiting reactant 1-bromopentane and 100% selectivity to 2′-pentyloxyacetophenone. This strategy eliminates separation problems and results in high reaction rates reducing the total reaction time. Moreover, the catalyst-rich third phase is recycled more than 7 times without loss in activity. The kinetics of the reaction are studied in great detail. There is a substantial reduction in activation energy under L-L-L PTC vis-a-vis L-L PTC, where the locale of the reaction is shifted from the organic phase to the third phase.
- Yadav, Ganapati D.,Desai, Neesha M.
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- Chromium-Catalyzed Linear-Selective Alkylation of Aldehydes with Alkenes
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We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz's reagent. Photochemical homolysis of the C-Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction proceeded with high functional group tolerance at ambient temperature under visible-light irradiation.
- Hirao, Yuki,Kanai, Motomu,Katayama, Yuri,Mitsunuma, Harunobu
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supporting information
(2020/11/18)
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- Cellulose oxidation and the use of carboxyl cellulose metal complexes in heterogeneous catalytic systems to promote suzuki-miyaura coupling and C?O bond formation reaction
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This work shows the modification of microcrystalline cellulose by the selective oxidation of primary hydroxyl groups to carboxylate groups by a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated system and its application as a heterogeneous ligand by ionic exchange with catalytic metals ions such as palladium, nickel and copper. Afterwards is described the application of the synthesized material as catalyst in coupling reactions such as Suzuki-Miyaura coupling and C?O bond formation reaction in different conditions, which are of great importance for the synthesis of drugs, natural products and new materials such as dendrimers, liquid crystals and polymers with magnetic and optical properties. The carboxyl cellulose matrix shows to have superior catalytic results as a ligand for all coupling reactions. Can be also highlighted the affinity of the carboxyl cellulose ligand in polar solvents such as water and alcohols and its application in mild conditions.
- Martins, Guilherme B. C.,Dos Santos, Marcelo R.,Rodrigues, Marcus V. R.,Sucupira, Renata R.,Meneghetti, Luisa,Monteiro, Adriano L.,Suarez, Paulo A. Z.
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p. 2064 - 2072
(2017/09/23)
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- Copper Catalyzed sp3 C-H Etherification with Acyl Protected Phenols
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A variety of acyl protected phenols AcOAr participate in sp3 C-H etherification of substrates R-H to give alkyl aryl ethers R-OAr employing tBuOOtBu as oxidant with copper(I) β-diketiminato catalysts [CuI]. Although 1°, 2°, and 3° C-H bonds may be functionalized, selectivity studies reveal a preference for the construction of hindered, 3° C-OAr bonds. Mechanistic studies indicate that β-diketiminato copper(II) phenolates [CuII]-OAr play a key role in this C-O bond forming reaction, formed via transesterification of AcOAr with [CuII]-OtBu intermediates generated upon reaction of [CuI] with tBuOOtBu.
- Salvador, Tolani K.,Arnett, Charles H.,Kundu, Subrata,Sapiezynski, Nicholas G.,Bertke, Jeffery A.,Raghibi Boroujeni, Mahdi,Warren, Timothy H.
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supporting information
p. 16580 - 16583
(2017/01/10)
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- Room temperature, metal-free arylation of aliphatic alcohols
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Diaryliodonium salts are demonstrated as efficient arylating agents of aliphatic alcohols under metal-free conditions. The reaction proceeds at room temperature within 90 min to give alkyl aryl ethers in good to excellent yields. Aryl groups with electron
- Ghosh, Raju,Lindstedt, Erik,Jalalian, Nazli,Olofsson, Berit
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- CATALYTIC C-H BOND ACTIVATION FOR THE SYNTHESIS OF ETHERS AND THIOETHERS
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Disclosed is a method for the transition metal-mediated oxidation of C-H bonds to form C-0 or C-S bonds. The methods are useful for the formation of ethers (R-OR') from alcohols, R'OH, and sp3 -hybridized C-H bonds in substrates, R-H. Aryl or heteroaryl acetates may also be used for C-H to C-OAr bond formation. The methods are also useful in the preparation of C-S bonds from acetyl-protected thiols, MeC(0)SR, and disulfides, RSSR. Advantageously, the methods minimize reaction steps, the handling of oxidized intermediates, and environmental impact.
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Page/Page column 46
(2014/01/08)
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- Heterogeneous palladium-catalyzed synthesis of aromatic ethers by solvent-free dehydrogenative aromatization: Mechanism, scope, and limitations under aerobic and non-aerobic conditions
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Starting from cyclohexanone derivatives and alcohols, both non-aromatic precursors, aryl ethers could be synthesized in good yields and with good selectivities in the presence of a catalytic amount of Pd/C, in one step, without added solvent, in a reaction vessel open to air. For less reactive substrates, the addition of 1-octene in a closed system under non-aerobic conditions improved the conversion. In addition, the catalyst could be recycled several times with no decrease in the yield of the aryl ether. The process was also used with tetralone derivatives and polyols. Several reactions were performed to propose a mechanism for this transformation. The formation of an enol ether followed by a dehydrogenation reaction seem to be the key steps of this reaction. Aryl ethers were prepared in good yields and with good selectivities in a solvent-free and heterogeneous catalytic dehydrogenative alkylation of cyclohexanones with various alcohols. Three different complementary routes were used, and for the first time, non-aerobic, safe conditions could be used. Moreover, the catalyst could be recycled several times with no decrease in the yield of the aryl ether. Copyright
- Sutter, Marc,Lafon, Romain,Raoul, Yann,Metay, Estelle,Lemaire, Marc
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supporting information
p. 5902 - 5916
(2013/09/23)
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- Higher-order zincates as transmetalators in alkyl-alkyl Negishi cross-coupling
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Negishi revisited: Higher-order alkyl zincates have been subjected to Negishi coupling with alkyl bromides. For the first time, coupling takes place in straight THF, i.e., without a salt additive and a high dielectric co-solvent. This provides evidence that it is the higher-order zincate that undergoes transmetalation to Pd, and not mono-anionic zincates or any of the other species present in the Schlenk equilibrium. Copyright
- McCann, Lucas C.,Hunter, Howard N.,Clyburne, Jason A. C.,Organ, Michael G.
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supporting information; experimental part
p. 7024 - 7027
(2012/10/18)
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- NOVEL SEMI-SYNTHETIC GLYCOPEPTIDES AS ANTIBACTERIAL AGENTS
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Semi-synthetic glycopeptides having antibacterial activity are described, in particular, the semi-synthetic glycopeptides described herein are made by chemical modification of the a glycopeptide (Compound A, Compound B, Compound H or Compound C) or the monosaccharide made by hydrolyzing the disaccharide moiety of the amino acid-4 of the parent glycopeptide in acidic medium to give the amino acid-4 monosaccharide; conversion of the monosaccharide to the amino-sugar derivative; acylation of the amino substituent on the amino acid-4 amino-substituted sugar moiety on these scaffolds with certain acyl groups; conversion of the amide group in amino acid-3 on these scaffolds to various acylamide, acylsulfonamide, acylsulfonylurea derivatives; aminomethylation with substituent containing sulfonamide or acylsulfonamide group on amino acid-7 through Mannich reaction; and conversion of the acid moiety on the macrocyclic ring of these scaffolds to certain substituted amides. Also provided are methods for the synthesis of the compounds, pharmaceutical compositions containing the compounds, and methods of use of the compounds for the treatment and/or prophylaxis of diseases, especially bacterial infections.
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- Synthesis of exo-3-ammo-7-azabicyclo[2.2.1]heptanes as a class of malarial aspartic protease inhibitors: Exploration of two binding pockets
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The increasing prevalence of drug-resisLant strains of malaria-causing Plasmodium parasites necessitates the development of therapeutic agents that inhibit new biochemical targets. We herein describe the design, synthesis, and in vitro evaluation of a class of inhibitors that target the malarial aspartic proteases known as the plasmepsins. The title compounds feature a 7-azanorbornane skeleton that bears an exo-amino function, which was designed to interact with the catalytic dyad of aspartic proteases while providing vectors for the attachment of binding elements that target the flap and S1/S3 binding pockets at. the enzyme active site. Their synthesis takes advantage of a solvent-free and highly diastereoselective conjugate addition of amines to bicyclic vinyl sulfones. Structural optimization based on a little-known conformational preference of aryl sulfones produced the most potent inhibitors of this new class. In vitro assays demonstrate that the title compounds are capable of potent (IC50 ≥ 1.0 nM) inhibition of plasmepsins, while remaining relatively weak inhibitors of the closely related human enzymes cathepsins D and E. The ideal occupation of the flap pocket is crucial for both potency and selectivity over the human proteases. Differently functionalized compounds were synthesized to gain new insights info the molecular recognition properties of this cavity. Wiley-VCH Verlag GmbH & Co. KGaA.
- Zuercher, Martina,Hof, Fraser,Barandun, Luzi,Schuetz, Andri,Schweizer, W. Bernd,Meyer, Solange,Bur, Daniel,Diederich, Francois
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supporting information; experimental part
p. 1707 - 1719
(2009/08/09)
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- The iridium-catalyzed decarbonylation of aldehydes under mild conditions
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The catalytic decarbonylation of aldehydes has been developed using commercially available [IrCl(cod)]2 and PPh3 under mild conditions, and the method could be widely applicable to various substrates with different functionalities. The Royal Society of Chemistry.
- Iwai, Tomohiro,Fujihara, Tetsuaki,Tsuji, Yasushi
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supporting information; experimental part
p. 6215 - 6217
(2009/05/06)
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- Structure-property correlations in model compounds of oligomer liquid crystals
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Structure-property correlations of the following model compounds for oligomer liquid crystals (LCs) have been investigated: monomers, C 6H5O(CH2)xCH3 (x = 4 and 5); dimers, C6H5O
- Sasanuma, Yuji,Ono, Tetsushi,Kuroda, Yoshihiko,Miyazaki, Emi,Hikino, Ken,Arou, Jun,Nakata, Kohji,Inaba, Hideaki,Tozaki, Ken-Ichi,Hayashi, Hideko,Yamaguchi, Kentaro
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p. 13163 - 13176
(2007/10/03)
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- A novel photoinduced reduction system of low-valent samarium species: Reduction of organic halides and chalcogenides, and its application to carbonylation with carbon monoxide
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Visible light irradiation is found to enhance the reducing ability of samarium diiodide (SmI2) dramatically. Organic halides (RCl, RBr, RI) and chalcogenides (RSPh, RSePh, RTePh) are smoothly reduced to the corresponding hydrocarbons by using this SmI2-hv system. The photoactivation can be also applied to ytterbium diiodide (YbI2) successfully. When the reduction of alkyl chlorides (RCl) by using the SmI 2-hv system is conducted under the pressure of carbon monoxide, unsymmetric ketones (RC(O)CH2R) are obtained as carbonylating products. A mechanistic pathway may involve the formation of acylsamarium species (RC(O)SmI2), which undergo dimerization, followed by reduction with SmI2, leading to the unsymmetric ketones.
- Sumino, Yukihito,Harato, Nami,Tomisaka, Yuri,Ogawa, Akiya
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p. 10499 - 10508
(2007/10/03)
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- Keratinocyte growth inhibitors and hydroxamic acid derivatives
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This invention relates to a keratinocyte-proliferation inhibitor comprising as active ingredient a compound having an activity of inhibiting the solubilization of heparin-binding EGF-like growth factor bound to cell membranes and a compound of the formula (I); or pharmaceutically acceptable salt thereof, wherein R1, R2, R3 are hydrogen atom or alkyl and X is substituted benzene or the like.
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- Synthesis and nucleophilic substitution reactions of mono α-fluoro ethers
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Mono α-fluoro ethers have been prepared by cleavage of α-alkoxy sulfoxides with diethylaminosulfur trifluoride (DAST) and by an exchange reaction of the corresponding α-chloro ether with tetrabutylammonium fluoride (TBAF). The reactivity of different α-fluoro ethers in some nucleophilic substitution reactions has been investigated. Copyright Acta Chemica Scandinavica 1999.
- Ringom, Rune,Benneche, Tore
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- Synthesis of 2-Phenoxyhexanal and 2-(o-Formylphenoxy)Hexanoic Acid and Its Derivatives
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The paper describes the synthesis of 2-phenoxyhexanal and 2-(o-formylphenoxy)hexanoic acid and its derivatives which are intermediate compounds in the synthesis of new heterocyclic compounds.Key words: 2-phenoxyhexanal, 2-phenoxyhexanoic acid derivatives, 2-butylbenzofurane
- Kwiecien, H.
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p. 661 - 666
(2007/10/02)
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- Copper(I) Halide Catalysed Synthesis of Alkyl Aryl and Alkyl Heteroaryl Ethers
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A number of alkyl aryl and alkyl heteroaryl ethers have been prepared from (hetero) aryl halides (mainly bromides) and sodium alkoxides, using copper(I)bromide as a catalyst.The influence of the main solvent, the halogen atom, reaction temperature and the presence of oxygen upon the rate and selectivity has been studied.Furthermore the decomposition of the catalyst and the reduction of the aryl halide are studied.
- Keegstra, Menno A.,Peters, Theo H. A.,Brandsma, Lambert
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p. 3633 - 3652
(2007/10/02)
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- THE HYDROGENOLYSIS OF ORGANIC HALIDES WITH ZINC DUST IN MICELLE
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A simple and useful synthetic procedure for hydrogenolysis of organic halides with zinc dust in micellar media is described.
- Jursic, Branko,Galosi, Andreja
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p. 1649 - 1654
(2007/10/02)
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- SYNTHETIC APPLICATION OF MICELLAR CATALYSIS. WILLIAMSON'S SYNTHESIS OF ETHERS
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A simple, rapid and efficient procedure for the preparation of di-alkyl, simple phenyl-alkyl and hindered phenyl-alkyl ethers has been developed.Based on the principle of micellar catalysis the method involves alkylation of the alkoxide or the phenoxide ion with an alkyl chloride at 80 deg C in the presence of cationic micelles.For the preparation of phenyl-alkyl ethers normal micelles were used, while for the di-alkyl ethers reverse micelles were more effective.By increasing the ionic strength of the solution the rate of formation of phenyl-alkyl ethers could be increased.
- Jursic, Branko
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p. 6677 - 6680
(2007/10/02)
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- The Effect of Two Terminal Alkoxy Groups on the Mesomorphic Properties of 4,4'-Disubstituted Phenylthiobenzoates
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A select variety of homologs of the dialkoxyphenylthiobenzoates were prepared.Their mesomorphic properties were determined by hot-stage polarizing microscopy and compared with those for the analogous RO-R' and R-OR' thioesters and esters.Unlike
- Neubert, Mary E.,Ziemnicka-Merchant, Barbara,Jirousek, Michael R.,Laskos, Stanley J.,Leonhardt, Darrin,Sharma, Ram B.
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p. 209 - 240
(2007/10/02)
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- p-Alkoxyphenylthionophosphine sulfide dimers
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Novel p-alkoxyphenylthionophosphine sulfide dimers useful for preparing thiopeptides from peptides.
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- POLYMER-SUPPORTED "MULTI-SITE" PHASE TRANSFER CATALYSTS
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Polystyrene-supported, "multi-site" quarternary phosphonium salts are highly effective phase transfer catalysts and are as or more effective than similar "single-site" materials.
- Idoux, John P.,Wysocki, Ronald,Young, Sherre,Turcot, Jeffrey,Ohlman, Charlene,Leonard, Russell
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p. 139 - 144
(2007/10/02)
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- POLY(ETHYLENE GLYCOL)S AS PHASE TRANSFER CATALYSTS IN THE ALKOXYLATION OF HALOBENZENES OF ALKYL ARYL ETHERS
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Mono and di-halobenzenes and alkoxide ions gave monoalkoxybenzenes, but no phenols, when catalyzed by high molecular weight poly(ethylene glycol)s as phase transfer catalysts.Bromobenzenes were more reactive than chlorobenzenes but gave more side products, and for alcohols the reactivity was primary>secondary>tertiary.
- Neumann, R.,Sasson, Y.
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p. 3437 - 3440
(2007/10/02)
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- EFFETS DE CRYPTANDS ET ACTIVATION DE BASES-Va ACTION DES HYDRURES ALCALINS SUR LES ACIDES FAIBLES-II. ALKYLATION DES ANIONS OBTENUS
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Phenoxides, alkoxides and potassium amidates generated by KH in THF or benzene at room temperature are easily alkylated in the presence of catalytic quantities of crytand, without affecting addition-elimination ratios.Thus, Williamson and Gabriel syntheses, as well as the alkylation of secondary amines, occur readily in mild conditions.
- Pasquini, M. A.,Goaller, R. Le,Pierre, J.L.
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p. 1223 - 1226
(2007/10/02)
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