- Fe-Catalyzed Aerobic Oxidative C-CN Bond Cleavage of Arylacetonitriles Leading to Various Esters
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Fe-catalyzed aerobic oxidative esterifications of arylacetonitriles with alcohols, tri alkoxsilanes, silicate esters, or borate esters have been developed. The acyl groups which were in situ generated via chemoselective C(CO)-CN bond cleavage were directly used as electrophiles, leading to corresponding aryl esters in good to excellent yields under molecular oxygen when attacked by alcohols or alcohol surrogates. Dioxygen serves as both oxidant and reactant in this protocol. The reaction has a very broad substrate scope. Cheap starting materials as well as environmentally benign and inexpensive iron catalyst and ideal oxidant O2 feature this transformation and make it a practical and sustainable protocol to afford esters.
- Kong, Weiguang,Li, Bingnan,Xu, Xuezhao,Song, Qiuling
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p. 8436 - 8443
(2016/09/28)
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- A facile, one-pot procedure for the conversion of aromatic aldehydes to esters, as well as thioesters and amides, via acyl hydrazide intermediates
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Herein we present an efficient method for the synthesis of esters from aromatic aldehydes via readily accessible acyl hydrazides. The developed reaction protocol is shown to be tolerant of a range of aromatic aldehydes, bearing various functionalities, as well as being amenable to the synthesis of thioesters and amides.
- Maruani, Antoine,Lee, Maximillian T. W.,Watkins, George,Akhbar, Ahmed R.,Baggs, Henry,Shamsabadi, André,Richards, Daniel A.,Chudasama, Vijay
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p. 3372 - 3376
(2016/01/16)
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- Inclusion complex containing epoxy resin composition for semiconductor encapsulation
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The invention is an epoxy resin composition for sealing a semiconductor, including (A) an epoxy resin and (B) a clathrate complex. The clathrate complex is one of (b1) an aromatic carboxylic acid compound, and (b2) at least one imidazole compound represented by formula (II): wherein R2 represents a hydrogen atom, C1-C10 alkyl group, phenyl group, benzyl group or cyanoethyl group, and R3 to R5 represent a hydrogen atom, nitro group, halogen atom, C1-C20 alkyl group, phenyl group, benzyl group, hydroxymethyl group or C1-C20 acyl group. The composition has improved storage stability, retains flowability when sealing, and achieves an effective curing rate applicable for sealing delicate semiconductors.
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- Generally applicable and efficient esterification of aldehydes with alcohols catalyzed by cyclopalladated ferrocenylimine
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The palladacycle-catalyzed esterification of a variety of aldehydes with alcohols was developed. This reaction allows formation of esters in moderate to excellent yields not only for various aldehydes but also alcohols. In addition, the esterification could proceed well under mild conditions with a low catalyst loading of 0.0625 mol%. Copyright
- Ma, Gaizhi,Leng, Yuting,Qiao, Huijie,Yang, Fan,Wang, Shiwei,Wu, Yangjie
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- Transition-metal-free aerobic oxidative cleavage of C-C bonds in α-hydroxy ketones and mechanistic insight to the reaction pathway
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Clear cut: For the title reaction, O2, the ideal oxidant, was used as the only oxidizing reagent. The dimer intermediate (see scheme) and isotopic labeling control experiments with 18O2 partially disclosed the reaction mec
- Liu, Hui,Dong, Chao,Zhang, Zeguang,Wu, Peiyu,Jiang, Xuefeng
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supporting information
p. 12570 - 12574
(2013/02/22)
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- Mechanistic investigation of oxidation of some substituted aromatic acetals with N-bromosuccinimide in acetonitrile medium - A kinetic approach
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The oxidation of meta- and para-substituted aromatic acetals by N-bromosuccinimide (NBS) to the corresponding esters and alkyl bromide, is first-order in [NBS] and [acetal]. The effect of substituents in the aromatic ring of some aromatic acetals [X-C6H4CH(OBu-B) 2] {X = H, p-OMe, p-Me, p-Cl, p-NO2, m-OMe, m-CI, m-NO2} on the kinetics of above oxidation has been studied in acetonitrile medium at various temperatures by iodometric method. The rate of the reaction increases with the increase in the dielectric constant of the medium. The stoichiometry of the reaction is found to be 1 : 1. A primary kinetic isotopic effect kH/kD of 1.8 is observed, which indicates the C-H bond cleavage of the aldehydic carbon in the rate determining step. The Hammett reaction constant (a) for the reaction is found to be -1.38 and -1.42 at 313 K and 323 K respectively. The Exner plot is found to be linear with the isokinetic temperature 132 K. The kinetic and activation parameters Ea, A, ΔH≠, ΔG≠ and ΔS≠ have been calculated. A mechanism involving simultaneous loss of H+ from the aldehydic carbon and expulsion of bromide ion with the formation of carbonium ion intermediate is proposed.
- Mathiyalagan
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p. 1499 - 1506
(2013/02/23)
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- Correlation analysis in the study of oxidation kinetics of aromatic acetals with N-bromosuccinimide in acetonitrile medium
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An attempt has been made to correlate the rate constants of substituted acetals with the chemical shifts of the benzylic proton of the acetals (log k2 vs δ). This correlation is similar to that of which is obtained between σ vs δ. The benzylic proton chemical shift in acetals is found to be the characteristics of acetals. The benzylic proton does not couple with other protons and hence appears as a singlet, which would ensure effective correlation.
- Mathiyalagan
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scheme or table
p. 865 - 868
(2012/04/10)
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- Regioselective nitration of deactivated mono-substituted benzenes using acyl nitrates over reusable acidic zeolite catalysts
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Nitration of benzonitrile was investigated using a nitric acid/acid anhydride/zeolite catalyst system under different reaction conditions. Trifluoroacetic and chloroacetic anhydrides were found to be the most active among the anhydrides tried. Also, zeolites Hβ and Fe3+β (Si/ Al = 12.5) were found to be the most active catalysts. For example, nitration of benzonitrile with trifluoroacetyl nitrate under reflux conditions in dichloromethane gave 3- and 4-nitrobenzonitriles in quantitative yield, of which the para-isomer represented 24-28%. The yield of para-isomer was improved to 33% when passivated Hβ was used under similar reaction conditions. This is easily the most para-selective nitration of benzonitrile ever recorded. Also, no ortho-isomer was formed under the conditions tried. The zeolite can be easily recovered, regenerated by heating and reused up to six times to give results similar to those obtained with a fresh sample of the catalyst. The nitration system was applied successfully to a range of deactivated mono-substituted benzenes to give para-isomers in significantly higher proportions than in the corresponding traditional nitration reactions.
- Smith, Keith,Ajarim, Mansour D.,El-Hiti, Gamal A.
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experimental part
p. 270 - 278
(2010/12/19)
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- Alumina sulfuric acid as a novel heterogeneous system for esterification of carboxylic acids in solvent free conditions
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Neat chlorosulfonic acid reacts with alumina to give alumina sulfuric acid (ASA) in which sulfuric acid is immobilised on the surface of alumina via a covalent bond. Carboxylic acids can be readily converted to their corresponding esters with a combination of ASA and alcohols in solvent free conditions.
- Sharghi, Hashem,Sarvari, Mona Hosseini,Eskandari, Razieh
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p. 488 - 491
(2007/10/03)
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- Linear free energy relationship and conformational effects on oxidation of aromatic acetals by pyridinium fluorochromate
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Kinetics of oxidation of aromatic acetals by pyridiniumfluorochromate (PFC) in aqueous acetic acid medium reveal that the reactions are second order, first order each in [acetal] and [PFC]. The presence of electron- withdrawing substituents in the benzene ring enhances the rate of oxidation while that of opposite one retards it. The small ρ value suggests a mechanism with little charge separation. The rate of oxidation depends on the nature of alkyl group and conformational effects.
- Ramakrishnan,Nambi
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p. 232 - 234
(2007/10/03)
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- Activity of substituted and unsubstituted bezaldehydes in reaction with butyl hypochlorite
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Substituted benzaldehydes under daylight react with butyl hypochlorite affording the corresponding butyl benzoates. Electron-donating substituents in the benzene ring of the aldehyde accelerate, and the electron-withdrawing one decelerate the reaction. The yields of the substituted butyl benzoates in all cases are lower than that of bytyl benzoate.
- Bikbulatov,Zorin,Zorina,Rakhmankulov
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p. 1633 - 1635
(2007/10/03)
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- An efficient general method for esterification of aromatic carboxylic acids
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Treatment of a variety of aromatic carboxylic acids with alcohols in the presence of thionyl chloride results in excellent yields of corresponding esters. This esterification system is compatible with a wide assortment of functional groups.
- Hosangadi, Bhaskar D.,Dave, Rajesh H.
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p. 6375 - 6378
(2007/10/03)
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- Mild, one-pot conversion of carboxylic acids into esters using phase transfer catalysis
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One-pot conversion of carboxylic acids into esters under the influence of phase transfer catalysis is reported.The method is shown to work satisfactorily for optically active acids having epimerisable α-hydrogen.
- Puntambekar, Hemalata M,Naik, D G,Kapadi, A H
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p. 793 - 794
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Aromatic Acetals by Ceric Ammonium Nitrate in Acetonitrile Medium
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Aromatic acetals of benzaldehyde and substituted benzaldehydes with n-butanol have been prepared and subjected to ceric ammonium nitrate oxidation in acetonitrile medium.The oxidation follows a total second order kinetics, first order each in and IV>.Variation in ionic strength of the medium and added nitrate ions have no influence on the rate.Decrease of dielectric constant of the medium decreases the rate.Activation parameters have been computed from Arrhenius plots.Activation enthalpy and entropy of the oxidation are linearly related.Both activation energy and frequency factor have been found to control the reaction.A probable mechanism has been proposed.
- Chockalingam, P.,Ramakrishnan, P. S.,Arulraj, S. J.,Nambi, K.
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p. 247 - 250
(2007/10/02)
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- Substituents Effect on the Reaction of Aromatic Acetals Over Aluminium Phosphate and Aluminium Sulphate Catalyst
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Aromatic acetals in the presence of aluminium phosphate (AP) catalyst at elevated temperatures yield the corresponding esters (b), ethers (c) and the parent aldehydes (d).These substrates over aluminium sulphate (AS) catalyst give only the esters (b) and aldehydes (d).The products distribution varies with temperature.Substituents in the ring also play a part in the reaction.
- Xavier, N.,Arulraj, S. J.
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p. 775 - 777
(2007/10/02)
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- Chromic Acid Oxidation of Aromatic Acetals in Aqueous Acetic Acid Medium. A Kinetic and Mechanistic Study
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When aromatic acetals of benzaldehyde and substituted-benzaldehyde with aliphatic alcohols are subjected to chromic acid oxidation in aqueous acetic acid medium, the corresponding esters are the main products.The oxidation follows a total second order kinetics, first order each in and VI>.The decrease of solvent polarity increases the rate of oxidation.The rate-determining step is assumed to be the elimination of proton from the complex species involving the acetal and chromium.The activation enthalpies and entropies of the oxidation of aromatic acetals are linearly related.
- Nambi, K.,Ahamed, K. A. Basheer,Arulraj, S. J.
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- REARRANGEMENT OF SUBSTITUTED AROMATIC ACETALS CATALYSED BY γ-ALUMINA
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Aromatic acetals over γ-alumina undergo rearrangement to give the corresponding esters (b) and ethers (c) in good yield.The product distribution varied unusually over the range of reaction temperatures.The effect of substituents has also been felt much in the study.Probable mechanisms have been suggested for the reaction.The catalyst has been characterized by various studies and the specific poisoning of the catalyst has been done with NH3, CO2 and H2S.
- Xavier, N.,Arulraj, S. J.
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p. 2875 - 2878
(2007/10/02)
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