- A one-pot and two-stage Baeyer-Villiger reaction using 2,2′-diperoxyphenic acid under biomolecule-compatible conditions?
-
An efficient oxidant named 2,2′-diperoxyphenic acid was newly developed, and it exhibited high stability as revealed by thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC). On applying this reagent in the Baeyer-Villiger oxidation, the reaction featured a markedly broad substrate scope and good functional group tolerance, giving rise to the corresponding products in good to excellent yields. Particularly, in the case of pure water or 1× Phosphate Buffered Saline (1× PBS) serving as the solvent, the protocol could work well, resulting in yields ranging from 81% to 98%. Moreover, the catalytic asymmetric version of the BV reaction was explored as well, affording the corresponding products in good yields and medium ee. Remarkably, the corresponding biological compatibility and greenness assessment indicated that this reagent had favorable application prospects in the biomedical and green manufacturing fields. Meanwhile, mechanistic studies including 18O isotope effect experiments and DFT computations suggested that this reaction followed the generally accepted mechanism of BV oxidation.
- Gan, Shaoyan,Shi, Lei,Song, Lijuan,Yin, Jingru,Yu, Zhiyou
-
supporting information
p. 2232 - 2239
(2022/04/03)
-
- Photo-on-Demand Synthesis of Vilsmeier Reagents with Chloroform and Their Applications to One-Pot Organic Syntheses
-
The Vilsmeier reagent (VR), first reported a century ago, is a versatile reagent in a variety of organic reactions. It is used extensively in formylation reactions. However, the synthesis of VR generally requires highly toxic and corrosive reagents such as POCl3, SOCl2, or COCl2. In this study, we found that VR is readily obtained from a CHCl3 solution containing N,N-dimethylformamide or N,N-dimethylacetamide upon photo-irradiation under O2 bubbling. The corresponding Vilsmeier reagents were obtained in high yields with the generation of gaseous HCl and CO2 as byproducts to allow their isolations as crystalline solid products amenable to analysis by X-ray crystallography. With the advantage of using CHCl3, which bifunctionally serves as a reactant and a solvent, this photo-on-demand VR synthesis is available for one-pot syntheses of aldehydes, acid chlorides, formates, ketones, esters, and amides.
- Liang, Fengying,Eda, Kazuo,Okazoe, Takashi,Wada, Akihiro,Mori, Nobuaki,Konishi, Katsuhiko,Tsuda, Akihiko
-
p. 6504 - 6517
(2021/05/06)
-
- Catalytic Aerobic Oxidation of Alkenes with Ferric Boroperoxo Porphyrin Complex; Reduction of Oxygen by Iron Porphyrin
-
We herein describe the development of a mild and selective catalytic aerobic oxidation process of olefins. This catalytic aerobic oxidation reaction was designed based on experimental and spectroscopic evidence assessing the reduction of atmospheric oxygen using a ferric porphyrin complex and pinacolborane to form a ferric boroperoxo porphyrin complex as an oxidizing species. The ferric boroperoxo porphyrin complex can be utilized as an in-situ generated intermediate in the catalytic aerobic oxidation of alkenes under ambient conditions to form oxidation products that differ from those obtained using previously reported ferric porphyrin catalysis. Moreover, the mild reaction conditions allow chemoselective oxidation to be achieved.
- Kimura, Kento,Kurahashi, Takuya,Matsubara, Seijiro,Murano, Shunpei
-
supporting information
p. 2493 - 2497
(2021/12/29)
-
- An efficient method to prepare aryl acetates by the carbonylation of aryl methyl ethers or phenols
-
Synthesis of valuable chemicals from lignin based compounds is critical for the application of biomass. Here, we develop a method of preparing aryl acetates by the carbonylation of aryl methyl ethers or phenols under low CO pressure. Good to excellent yields of aryl acetates were obtained using different substrates, and a possible reaction mechanism was proposed by conducting a series of control experiments. This method may provide a potential way for the utilization of lignin.
- Zhang, Dejin,Yang, Guoqiang,Xiong, Junping,Liu, Jia,Hu, Xingbang,Zhang, Zhibing
-
p. 2683 - 2687
(2021/02/16)
-
- Palladium-Catalyzed Direct Dicarbonylation of Amines with Ethylene to Imides
-
The selective and effective conversion of low-cost and simple bulk chemicals into high value-added products through catalytic strategy has a wide range of practical significance. Here, a palladium-catalyzed method for the direct and efficient dicarbonylation of amines with basic industrial feedstock ethylene to imide has been developed. Moderate to excellent yields of the desired imides can be produced from readily available amines in a straightforward manner.
- Kuai, Chang-Sheng,Wang, Le-Cheng,Wu, Xiao-Feng,Xu, Jian-Xing
-
supporting information
(2022/01/04)
-
- Method for preparing organic carboxylic ester through combined catalysis of aryl bidentate phosphine ligand
-
The invention discloses a method for preparing organic carboxylic ester by combined catalysis of an aryl bidentate phosphine ligand. The method comprises the following steps: under the action of a palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, carrying out a hydrogen esterification reaction on terminal olefin, carbon monoxide and alcohol so as to generate theorganic carboxylic ester with one more carbon than olefin. According to the invention, by adoption of the palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, good catalytic activity and selectivity for the hydrogen esterification reaction of the olefin are achieved, and olefin carbonylation to synthesize organic carboxylic ester can be efficiently catalyzed. Thearyl bidentate phosphine ligand has a rigid skeleton structure of a rigid ligand and the flexibility of a flexible ligand, so the aryl bidentate phosphine ligand has proper flexibility due to the characteristic that the aryl bidentate phosphine ligand is soft and rigid, and a most favorable coordination mode and a stable active structure in space are favorably formed. In addition, the aryl bidentate phosphine ligand has the advantages of high stability, simple and convenient synthesis method and the like; and a novel industrial technology is provided for production of organic carboxylate compounds.
- -
-
Paragraph 0040
(2020/05/29)
-
- Rhodium-Catalyzed Carbonylative Coupling of Alkyl Halides with Phenols under Low CO Pressure
-
A rhodium-catalyzed carbonylative transformation of alkyl halides under low pressure of CO has been developed. This robust catalyst system allows using phenols as the carbonylative coupling partner and, meanwhile, exhibits high functional group tolerance and good chemoselectivity. Substrates even with a large steric hindrance group or multiple reaction sites can be selectively converted into the desired products in good to excellent yields. A gram-scale experiment was performed and delivered an almost quantitative amount of the product. Control experiments were performed as well, and a possible reaction mechanism is proposed.
- Ai, Han-Jun,Li, Chong-Liang,Wang, Hai,Wu, Xiao-Feng
-
p. 5147 - 5152
(2020/05/27)
-
- Hydrogenation reaction method
-
The invention relates to a hydrogenation reaction method, and belongs to the technical field of organic synthesis. The hydrogenation reaction method provided by the invention comprises the following steps: carrying out a hydrogen transfer reaction on a hydrogen acceptor compound, pinacol borane and a catalyst in a solvent in the presence of proton hydrogen, so that the hydrogen acceptor compound is subjected to a hydrogenation reaction; the catalyst is one or more than two of a palladium catalyst, an iridium catalyst and a rhodium catalyst; the hydrogen acceptor compound comprises one or morethan two functional groups of carbon-carbon double bonds, carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogentriple bonds and epoxy. The method is mild in reaction condition, easy to operate, high in yield, short in reaction time, wide in substrate application range, suitable for carbon-carbon double bonds,carbon-carbon triple bonds, carbon-oxygen double bonds, carbon-nitrogen double bonds, nitrogen-nitrogen double bonds, nitryl, carbon-nitrogen triple bonds and epoxy functional groups, good in selectivity and high in reaction specificity.
- -
-
Paragraph 0034; 0117-0120
(2020/05/14)
-
- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
-
A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
-
supporting information
p. 4119 - 4129
(2020/08/10)
-
- Reduction of Activated Alkenes by PIII/PV Redox Cycling Catalysis
-
The carbon–carbon double bond of unsaturated carbonyl compounds was readily reduced by using a phosphetane oxide catalyst in the presence of a simple organosilane as the terminal reductant and water as the hydrogen source. Quantitative hydrogenation was observed when 1.0 mol % of a methyl-substituted phosphetane oxide was employed as the catalyst. The procedure is highly selective towards activated double bonds, tolerating a variety of functional groups that are usually prone to reduction. In total, 25 alkenes and two alkynes were hydrogenated to the corresponding alkanes in excellent yields of up to 99 %. Notably, less active poly(methylhydrosiloxane) could also be utilized as the terminal reductant. Mechanistic investigations revealed the phosphane as the catalyst resting state and a protonation/deprotonation sequence as the crucial step in the catalytic cycle.
- Longwitz, Lars,Werner, Thomas
-
supporting information
p. 2760 - 2763
(2020/02/05)
-
- BETA-HYDROXYETHYLAMINES FOR USE IN THE TREATMENT OR PREVENTION OF NON-ALCOHOLIC FATTY LIVER DISEASES
-
There is herein provided a compound of formula (I) or a pharmaceutically acceptable salt thereof, for use in the treatment of a non-alcoholic fatty liver disease (NAFLD), such as non-alcoholic steatohepatitis (NASH), wherein X, R1, R2, R3 and n have meanings as provided in the description.
- -
-
Page/Page column 51
(2019/04/11)
-
- Method for synthesizing esters
-
The invention belongs to the technical field of organic chemical synthesis, and discloses a method for synthesizing esters. The method is characterized in that a dehydration reaction of carboxylic acid and alcohols is promoted by common imidazole quaternary ammonium salts, thiazole quaternary ammonium salts or triazole quaternary ammonium salts and fluorides to synthesize the esters. The method has the advantages of cheap raw materials, simple process, greenness, safety, high efficiency and environmental protection, and is suitable for industrial production.
- -
-
Paragraph 0021-0023
(2019/11/29)
-
- Linear polystyrene-stabilized Rh(III) nanoparticles for oxidative coupling of arylboronic acids with alkenes in water
-
Linear polystyrene-stabilized Rh(III) nanoparticles (PS-Rh(III)NPs) were obtained when an aqueous solution of RhCl3 was stirred at 90 °C in the presence of KOH, 4-methylphenylboronic acid, and linear polystyrene, as indicated by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). PS-Rh(III)NPs exhibited high catalytic activity for the oxidative coupling of arylboronic acids with alkenes. In contrast, PS-Rh(0)NPs prepared with NaBH4 had little activity for the same reaction.
- Ohtaka, Atsushi,Fukui, Shiho,Sakon, Akira,Hamasaka, Go,Uozumi, Yasuhiro,Shinagawa, Tsutomu,Shimomura, Osamu,Nomura, Ry?ki
-
-
- COMPOUNDS FOR THE TREATMENT OF HYPERGLYCAEMIA
-
There is herein provided a compound of formula (I) or a pharmaceutically acceptable salt thereof, for use in the treatment of hyperglycaemia or a disorder characterized by hyperglycaemia, such as type 2 diabetes, wherein X, R1, R2, R3 and n have meanings as provided in the description.
- -
-
Page/Page column 54
(2017/09/28)
-
- Palladium-catalyzed Suzuki-Miyaura coupling of aryl esters
-
The Suzuki-Miyaura coupling is among the most important C-C bond-forming reactions available due to its reliability, chemoselectivity, and diversity. Aryl halides and pseudohalides such as iodides, bromides, and triflates are traditionally used as the electrophilic coupling partner. The expansion of the reaction scope to nontraditional electrophiles is an ongoing challenge to enable an even greater number of useful products to be made from simple starting materials. Herein, we present how an NHC-based Pd catalyst can enable Suzuki-Miyaura coupling where the C(acyl)-0 bond of aryl esters takes on the role of electrophile, allowing the synthesis of various ketone-containing products. This contrasts known reactions of similar esters that provide biaryls via nickel catalysis. The underlying cause of this mechanistic divergence is investigated by DFT calculations, and the robustness of esters compared to more electrophilic acylative coupling partners is analyzed.
- Halima, Taoufik Ben,Zhang, Wanying,Yalaoui, Imane,Hong, Xin,Yang, Yun-Fang,Houk, Kendall N.,Newman, Stephen G.
-
supporting information
p. 1311 - 1318
(2017/05/16)
-
- 14-MEMBERED KETOLIDES AND METHODS OF THEIR PREPARATION AND USE
-
Provided herein are methods of preparing new 14-membered ketolides via coupling of an eastern and western half moiety, followed by macrocyclization, and optional functionalization. Intermediates in the synthesis of these ketolides including the eastern and western halves are also provided. Pharmaceutical compositions and methods of treating infectious diseases and inflammatory conditions using these ketolides are also provided.
- -
-
Paragraph 00579
(2016/05/02)
-
- Hydroxy-Directed Amidation of Carboxylic Acid Esters Using a Tantalum Alkoxide Catalyst
-
We describe herein a new strategy for the chemoselective synthesis of amides by using a metal-catalyzed hydroxy-directed reaction. A hydroxy group located at the β-position of an ester group promoted the activation of a carbonyl group with a tantalum alkoxide catalyst followed by amidation reactions, leading to a wide variety of β-hydroxyamides with excellent chemeselectivity. The chemoselective amidation strategy can be extended to the catalytic synthesis of dipeptide derivatives, which remains challenging research subjects in modern organic synthesis.
- Tsuji, Hiroaki,Yamamoto, Hisashi
-
supporting information
p. 14218 - 14221
(2016/11/13)
-
- The insertion of arynes into the O-H bond of aliphatic carboxylic acids
-
The insertion of arynes into the O-H bond of aliphatic carboxylic acids promoted by sodium carboxylates is described. The reactions led to the formation of aryl carboxylates in good yields with good chemoselectivities under mild conditions.
- Wen, Chunxiao,Chen, Qian,He, Zhenwen,Yan, Xinxing,Zhang, Changyuan,Du, Zhiyun,Zhang, Kun
-
supporting information
p. 5470 - 5473
(2015/09/15)
-
- How much does the hybridization of a carbon atom affect the transmission of the substituent effect on the chemical shift?
-
1H and 13C NMR spectra of aryl esters of propionic acid, acrylic acid, and propiolic acid were systematically examined to find out the substituent effect on the chemical shift. The values of the chemical shift of the carbonyl carbon showed an inverse correlation with the Hammett ?3 values, and the magnitude of the slope was the largest with the propiolates. The ?± carbons of acrylates and propiolates also showed an inverse correlation with much smaller values of the slopes than those of the carbonyl carbons; but those of the propionates showed absolutely no correlation. However, the ?2 carbons of acrylates and propiolates showed normal correlation with larger values of the slopes. The signs and the magnitudes of the slopes may be understood by the transmission of the substituent electronic effect through bonds as well as through space. The propiolyloxy group also showed a significantly large effect on the 13C chemical shift values of the benzene ring.
- Jeong, Eun Jeong,Lee, In-Sook Han
-
p. 295 - 299
(2015/03/03)
-
- Tris(pentafluorophenyl)borane catalyzed acylation of alcohols, phenols, amines, and thiophenols under solvent-free condition
-
The acylation of alcohols, phenols, amines, and thiophenols was accomplished with 0.5 mol % of tris(pentafluorophenyl)borane [B(C 6F5)3] at ambient temperature under solvent-free condition. Major advantages of this method include high yield, short reaction time, simple procedure, compatibility with sensitive protecting groups as well as other functional groups, absence of racemization of optical active compounds, and epimerization of sugars.
- Prajapti, Santosh Kumar,Nagarsenkar, Atulya,Babu, Bathini Nagendra
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p. 1784 - 1787
(2014/03/21)
-
- MACROLIDES AND METHODS OF THEIR PREPARATION AND USE
-
Provided herein are methods of preparing macrolides by the coupling of an eastern and western half, followed by macrocyclization, to provide macrolides, including both known and novel macrolides. Intermediates in the synthesis of macrolides including the eastern and western halves are also provided. Pharmaceutical compositions and methods of treating infectious diseases and inflammatory conditions using the inventive macrolides are also provided. A general diastereoselective aldol methodology used in the synthesis of the western half is further provided.
- -
-
Paragraph 00667
(2014/10/18)
-
- O-acylation of substituted phenols with various alkanoyl chlorides under phase-transfer catalyst conditions
-
Esterification of several types of mono-and disubstituted phenols with various mono-and dialkanoyl chlorides was performed in phase-transfer catalysis conditions, using tetrabutylammonium chloride in a mixture of aqueous NaOH and dichloromethane. The process is particularly efficient (almost quantitative yields) as well as rapid (only 5 min reaction time, at a temperature of0°C). Taylor & Francis Group, LLC.
- Simion, Alina Marieta,Hashimoto, Iwao,Mitoma, Yoshiharu,Egashira, Naoyoshi,Simion, Cristian
-
experimental part
p. 921 - 931
(2012/02/01)
-
- Comparisons of O-acylation and Friedel-Crafts acylation of phenols and acyl chlorides and Fries rearrangement of phenyl esters in trifluoromethanesulfonic acid: Effective synthesis of optically active homotyrosines
-
Reactions involving phenol derivatives and acyl chlorides have to be controlled for competitive O-acylations and C-acylations (Friedel-Crafts acylations and Fries rearrangements) in acidic condition. The extent for these reactions in trifluoromethanesulfonic acid (TfOH), which is used as catalyst and solvent, is examined. Although diluted TfOH was needed for effective O-acylation, concentrated TfOH was required for effective C-acylations in mild condition. These results have been applied to the novel synthesis of homotyrosine derivatives. Both Fries rearrangement of N-TFA-Asp(OBn)-OMe and Friedel-Crafts acylation of phenol with N-TFA-Asp(Cl)-OMe in TfOH afforded the homotyrosine skeleton, followed by reduction and deprotection afforded homotyrosines maintaining stereochemistry of Asp as an optically pure form.
- Murashige, Ryo,Hayashi, Yuka,Ohmori, Syo,Torii, Ayuko,Aizu, Yoko,Muto, Yasuyuki,Murai, Yuta,Oda, Yuji,Hashimoto, Makoto
-
experimental part
p. 641 - 649
(2011/03/19)
-
- Nickel-catalyzed cross-coupling of aryl bromides with tertiary grignard reagents utilizing donor-functionalized N-heterocyclic carbenes (NHCs)
-
Metal-catalyzed cross-coupling reactions are among the most important transformations in organic synthesis, allowing the efficient construction of complex structures from simpler, readily available building blocks.Many applications in large and small-scale synthesis can be found in different areas such as agrochemicals, pharmaceuticals and supramolecular chemistry. Whereas the coupling of sp2-hybridized carbon atoms in either reaction partner is well established, the use of CACHTUNGTRENUNG(sp3)-hybridized substrates presents some challenges. Catalytic cross-coupling of sterically hindered tertiary alkyl substrates is especially difficult, generally resulting in low yields, and thus, only few reports exist.[27] A big challenge in this field is not only to get the required level of reactivity, but also to overcome competing pathways like β-hydride elimination, hydrodehalogenation or isomerization
- Lohre, Claudia,Droege, Thomas,Wang, Congyang,Glorius, Frank
-
supporting information; experimental part
p. 6052 - 6055
(2011/06/25)
-
- α-Aroyloxyaldehydes: Scope and limitations as alternatives to α-haloaldehydes for NHC-catalysed redox transformations
-
α-Aroyloxyaldehydes are readily prepared bench stable synthetic intermediates. Their ability to act as α-haloaldehyde surrogates for NHC-promoted redox esterifications and in [4+2] cycloadditions is described.
- Ling, Kenneth B.,Smith, Andrew D.
-
supporting information; experimental part
p. 373 - 375
(2011/02/24)
-
- Erbium(III) chloride: A very active acylation catalyst
-
Erbium(iii) chloride is a powerful catalyst for the acylation of alcohols and phenols. The reaction works well for a large variety of simple and functionalized substrates by using different kinds of acidic anhydrides (Ac 2O, (EtCO)2O, (PriCO)2O, (Bu tCO)2O, and (CF3CO)2), without isomerization of chiral centres. Moreover, the catalyst can be easily recycled and reused without significant loss of activity. CSIRO 2007.
- Dalpozzo, Renato,De Nino, Antonio,Maiuolo, Loredana,Oliverio, Manuela,Procopio, Antonio,Russo, Beatrice,Tocci, Amedeo
-
-
- O-arylation of carboxylic acids using (phenyl)[2-(trimethylsilyl)phenyl] iodonium triflate as a precursor of arynes
-
Using (phenyl)[2-(trimethylsilyl)phenyl]iodonium triflate as a precursor of arynes, Larock's method for O-arylation of carboxylic acids and arynes was developed. A variety of acids including simple aliphatic carboxylic acids, aromatic carboxylic acids, allenoic acids, and p-toluenesulfonic acid under mild reaction conditions could generate the aryl esters. Copyright Taylor & Francis Group, LLC.
- Xue, Jian,Huang, Xian
-
p. 2179 - 2185
(2008/02/05)
-
- Conjugate reduction of α,β-unsaturated esters and amides with tributyltin hydride in the presence of magnesium bromide diethyl etherate
-
We report herein that the conjugate reduction of α,β-unsaturated esters and amides, such as aryl acrylates, pantolactone esters of acrylic acids, diethyl itaconate and N-crotonylcamphorsultam, with tributyltin hydride proceeded in moderate to high yields in the presence of magnesium bromide diethyl etherate. The effect of metal halide enhancing the yields is also described.
- Hirasawa, Satomi,Tajima, Yoshie,Kameda, Yoko,Nagano, Hajime
-
p. 10930 - 10938
(2008/02/12)
-
- An eco-friendly method for the synthesis of aryl and alkyl esters of carboxylic acids using acid activated Indian bentonite
-
Esterification of various carboxylic acids with phenol and alcohols has been achieved using acid activated Indian bentonite (AAIB) as catalyst. The catalyst is versatile, and the reaction is found to work well for primary, secondary and tertiary alcohols. The yields are very good under specific reaction conditions.
- Vijayakumar,Iyengar, Pushpa,Nagendrappa, Gopalpur,Prakash, B. S. Jai
-
p. 922 - 925
(2007/10/03)
-
- O-acylation mechanism of p-substituted phenols with various alkanoyl chlorides under phase transfer catalysis conditions
-
The phenolic ester synthesis between equimolecular amounts of phenols and various alkanoyl chlorides in the presence of aqueous sodium hydroxide solution in a two-phase system (20 mL of each 10% NaOH and dicloromethane, respectively) was reinvestigated under PTC conditions (10 mmol of tetrabutyl ammonium chloride, BNC). The esterification was complete within several minutes and the obtained ester was in high purity. For example, phenyl acetate was obtained quantitatively at 0°C in 5 minutes using a stoichiometric amount of BNC. This acylation procedure is technically simple and does not require anhydrous conditions. A bimolecular electrophilic attack of alkanoyl chloride against the ion-pair in the organic phase, which was formed between the quaternary ammonium cation and the phenoxide anion, must be a rate-determining step, because a plot of the logarithm of relative rate constants of various alkanoyl chlorides vs Taft's polar substituents constants (taking into account the steric constants, Es) gave a good linear relationship. We have found a simple, rapid, convenient, easily separating and efficient PTC technique to synthesize phenolic esters.
- Hashimoto, Iwao,Kawaji, Takatoshi,Mitoma, Yoshiharu,Simion, Alina M.,Semion, Cristian,Ishimoto, Keiko,Prakash, G.K. Surya,Olah, George A.,Tashiro, Masashi
-
p. 149 - 155
(2007/10/03)
-
- Conjugate reduction of aryl acrylates with tributyltin hydride in the presence of magnesium bromide diethyl etherate
-
The conjugate reduction of aryl acrylates performed with tributyltin hydride in the presence of magnesium bromide diethyl etherate in dichloromethane gave the corresponding saturated esters in moderate to high yields. The reduction of α-methylene-γ-benzyloxycarboxylic acid esters proceeded syn-selectively, but α-methylene-β-oxycarboxylic acid esters afforded reductive elimination products under the reaction conditions.
- Hirasawa, Satomi,Nagano, Hajime,Kameda, Yoko
-
p. 2207 - 2209
(2007/10/03)
-
- Microwave oven synthesis of esters promoted by imidazole
-
Using imidazole as promotion agent, primary, secondary and phenolic alcohol compounds were esterified with aliphatic and aromatic carboxylic acid anhydrides. Heating a ternary mixture of alcohol, anhydride and imidazole in an unmodified microwave oven produced esters in low to high yields, depending on the steric bulk of the alcohol.
- Hirose, Takuji,Kopek, Benjamin G.,Wang, Zhao-Hui,Yusa, Ritsuko,Baldwin, Bruce W.
-
p. 1831 - 1833
(2007/10/03)
-
- Electron-withdrawing substituents decrease the electrophilicity of the carbonyl carbon. An investigation with the aid of 13C NMR chemical shifts, v(C=O) frequency values, charge densities, and isodesmic reactions to interprete substituent effects on reactivity
-
13C NMR chemical shifts and v(C=O) frequencies have been measured for several series of phenyl-or acyl-substituted phenyl acetates and for acyl-substituted methyl acetates to investigate the substituent-induced changes in the electrophilic character of the carbonyl carbon. Charge density, bond order, and energy calculations have also been performed. The spectroscopic and charge density results indicate that opposite to the conventional thinking, electron-withdrawing substituents do not increase the electrophilicity of the carbonyl carbon but instead decrease it. On the other hand, reaction energies of the isodesmic reactions designed show that electron-withdrawing substituents destabilize the carbonyl derivatives investigated. So, a significant ground-state destabilization of carboxylic acid esters, and carbonyl compounds in general, due to the decreased resonance stabilization, is proposed as a novel concept to explain both the increase in their reactivity and the changes in the chemical shifts and carbonyl frequencies induced by electron-withdrawing substituents.
- Neuvonen, Helmi,Neuvonen, Kari,Koch, Andreas,Kleinpeter, Erich,Pasanen, Paavo
-
p. 6995 - 7003
(2007/10/03)
-
- Auxiliary accelerated reactions: Towards the use of catalytic chiral auxiliaries
-
In competition experiments, the acceleration of reactivity of alkenes tethered to pyridyl groups compared with the corresponding alkenes tethered to phenyl groups in the presence of transition metals was demonstrated for two reaction types: Diels-Alder cycloaddition of enoate esters and catalytic hydrogenation of allylic and homoallylic ethers. The rate accelerations observed are of crucial importance in the development of a new concept for asymmetric catalysis: chiral auxiliaries which can function in a catalytic manner.
- Westwell, Andrew D.,Williams, Jonathan M. J.
-
p. 13063 - 13078
(2007/10/03)
-
- Auxiliary accelerated reactions: Catalytic hydrogenation
-
In competition experiments, alkenes tethered to pyridyl groups were found to undergo indium catalysed hydrogenation more quickly than alkenes tethered to phenyl groups. This is in marked contrast to the results for hydrogenation of some of the individual substrates where alkenes tethered to pyridyl groups were reduced much more slowly than their phenyl counterparts.
- Westwell, Andrew D.,Williams, Jonathan M. J.
-
-
- Ozone-mediated Reaction of Anilides and Phenyl Esters with Nitrogen Dioxide: Enhanced Ortho-reactivity and Mechanistic Implications
-
In the presence of ozone, anilides 1 can be nitrated rapidly with nitrogen dioxide in chloroform at 0 deg C to give a high proportion of ortho-nitro derivatives (ortho:para = 1.2-4.4) in good yields.The phenyl esters 15 can be similarly nitrated on the aromatic ring without significant cleavage of the ester bond, giving a mixture of isomeric nitro derivatives in which the ortho-isomer predominantes (ortho:para = 1.1-1.5).The oridin of the enhanced ortho reactivity is discussed in terms of an electron-transfer process involving the nitrogen trioxide as initial electrophile.
- Suzuki, Hitomi,Tatsumi, Atsuo,Ishibashi, Taro,Mori, Tadashi
-
p. 339 - 344
(2007/10/02)
-
- Regioselective Acylation of Anisole with Carboxylic Acids over HZSM-5 Catalyst
-
Over a HZSM-5 catalyst, the liquid-phase acylation of anisole with carboxylic acid gave the phenyl carboxylic ester at lower temperatures (423 K) 4-acyl anisole was the predominant product.
- Wang, Q. L.,Ma, Yudao,Ji, Xingdong,Yan, Hao,Qiu, Qin
-
p. 2307 - 2308
(2007/10/02)
-
- A REEXAMINATION OF THE RETRO-FRIES REARRANGEMENT OF SOME o-HYDROXYKETONES
-
The retro-Fries rearrangement, catalyzed by protic and Lewis acids, was studied for some o-hydroxyketones.The results are consistent with the mechanism of an heterolytic cleavage and rearrangement.It appears that, in general, Lewis acids do not induce the retro-Fries rearrangement of o-hydroxyketones.However, in certain cases, it may be brought about the presence of a protic acid generated in situ, from a solvent-catalyst interaction.
- Martin, Robert,Lafrance, Jean Ronald,Demerseman, Pierre
-
p. 539 - 548
(2007/10/02)
-
- Convenient One Pot Synthesis of Esters of Carboxylic Acids from Alkyl or Aryl Halides
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Esters of carboxylic acids were readily synthesized from alkyl or aryl halides by reacting the corresponding Grignard reagents with dimethyl, diphenyl or ethylene carbonates.
- Satyanarayana, G.,Sivaram, S.
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p. 3273 - 3276
(2007/10/02)
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- Studies in Bile Salt Solutions. XIV. Electronic, Charge and Steric Substrate-Effects on the Esterase Activity of Bile-Salt-Stimulated Human Milk Lipase. Hydrolysis of 4-Substituted Phenyl Propionates
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The rate constants of hydrolysis of series of 4-substituted phenyl propionates, catalysed by bile-salt-stimulated human milk lipase in the absence and presence of cholate or taurocholate stimulation, have been measured at pH 7.3, 310.5 K.There is little evidence for an alkyl site electronic interaction in the rate-determining step of the esterolytic reaction.However, a negatively charged substrate or an amido-substituent caused an inhibition of unstimulated esterase activity.In the presence of the bile-salt cofactors, esterolytic activity against charged substrates may be stimulated or inhibited, depending on the proximity of the charge to the steroidal side chain and the subsequent substrate-interaction within the surrounding environment of the active site.It has been confirmed that bile-salt-stimulated lipase is not an amidase, but that an amide, of the correct geometry, may occupy the active site and restrict esterase activity.
- O'Connor, Charmian J.,Mitha, Amin S. H.
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p. 259 - 269
(2007/10/02)
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- OXYGENATION OF AROMATIC AND ALIPHATIC HYDROCARBONS BY A NEW REAGENT SYSTEM, Fe(CH3CN)6(2+)-H2O2-Ac2O: AN EFFECTIVE MODEL REAGENT FOR MONO-OXYGENASE
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Reactions of aromatic and aliphatic hydrocarbons with a new system, Fe(CH3CN)6(2+) - H2O2 - Ac2O in CH3CN, gave oxygenation products with fairly high reaction efficiency ( Tables I and II )compared to known to reagent systems used as enzyme models for mono-oxygenases.Investigations of the mechanism of these reactions indicated the involvement of either complex C.FeIV(OH)(OAc)(2+), or complex D, FeIV(OAc)(2+), dependig on the organic substrate.Keywords-oxygenation; aromatic hydrocarbon; aliphatic hydrocarbon; hexakisacetonitrile iron(II) perchlorate; hydrogen peroxide; enzyme model; mono-oxygenase
- Kotani, Eiichi,Kobayashi. Shigeki,Ishii, Yoko,Tobinaga, Seisho
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p. 4671 - 4679
(2007/10/02)
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- Sodium Borohydride-Carboxylic Acid Systems - A new Method of Acylation of Alcohols, Phenols and Thiophenols
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A new method of acylation of alcohols, phenols and thiophenols in sodium borohydride-carboxylic acid system is described.A plausible mechanism of this acylation through tetraacyloxyborate derivative has been postulated.
- Prashad, Mahavir,Jigajinni, Veerappa B.
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p. 822 - 823
(2007/10/02)
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