- [Co(MeTAA)] Metalloradical Catalytic Route to Ketenes via Carbonylation of Carbene Radicals
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An efficient synthetic strategy towards beta-lactams, amides, and esters involving “in situ” generation of ketenes and subsequent trapping with nucleophiles is presented. Carbonylation of carbene radical intermediates using the cheap and highly active cobalt(II) tetramethyltetraaza[14]annulene catalyst [Co(MeTAA)] provides a convenient one-pot synthetic protocol towards substituted ketenes. N-tosylhydrazones are used as carbene precursors, thereby bridging the gap between aldehydes and ketenes. Activation of these carbene precursors by the metalloradical cobalt(II) catalyst affords CoIII-carbene radicals, which subsequently react with carbon monoxide to form ketenes. In the presence of a nucleophile (imine, alcohol, or amine) in the reaction medium the ketene is immediately trapped, resulting in the desired products in a one-pot synthetic protocol. The β-lactams formed upon reaction with imines are produced in a highly trans-selective manner.
- Chirila, Andrei,van Vliet, Kaj M.,Paul, Nanda D.,de Bruin, Bas
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supporting information
p. 2251 - 2258
(2018/04/09)
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- Carboxyl activation of 2-mercapto-4,6-dimethylpyrimidine through n-acyl-4,6-dimethylpyrimidine-2-thione: A chemical and spectrophotometric investigation
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2-Mercapto-4,6-dimethylpyrimidine, as effective carboxyl activating group, has been successfully proved by converting it into respective acyl derivatives and the subsequent conversion to the amides and esters respectively using amines, amino alcohols and alcohols. The aminolysis and esterification were monitored chemically and spectrophotometrically. This paved way to establish that the above mercaptopyrimidine derivative is an efficient carboxyl activating group applicable in solid phase peptide synthesis.
- Rajan
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p. 287 - 291
(2015/01/30)
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- Efficient microwave-assisted esterification reaction employing methanesulfonic acid supported on alumina as catalyst
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A rapid and efficient protocol assisted by microwave irradiation for the synthesis of esters using methanesulfonic acid (CH3SO3H) supported on Al2O3 (AMA) as catalyst and free of solvent is described. The products were obtained in good yields and purity, with reduced reaction time, and the process is simple and environmentally benign. Copyright
- Fabian, Lucas,Gomez, Matias,Kuran, Juan A. Caturelli,Moltrasio, Graciela,Moglioni, Albertina
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p. 2386 - 2392
(2014/07/22)
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- A method for esterification reaction rate prediction of aliphatic monocarboxylic acids with primary alcohols in 1,4-dioxane based on two parametrical taft equation
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Esterification reaction rates of aliphatic monocarboxylic acids with primary alcohols in 1,4-dioxane as inert solvent were investigated. Acids were esterified with 1-propanol and alcohols with acetic acid as model reactants at a constant temperature of 60°C, at a fixed ionic strength and pH in a batch reactor with a constant volume. For evaluation of reaction rates, an exact kinetic equation for the equilibrium reaction was applied. Under these conditions and for low reactants, concentrations reaction rate depends only on the structure of reactants and, therefore, can be predicted by a correlation equation with two Taft coefficients (inductive and steric effects). From these equations, it is possible to estimate the esterification reaction rate constant for other acid-alcohol pairs. This methodology may also be suitable for other kinetic systems measured under comparable experimental conditions.
- Vojtko, Jan,Tomcik, Peter
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p. 189 - 196
(2014/02/14)
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- PROCESS FOR SYNTHESIZING PHENYLACETIC ACID BY CARBONYLATION OF TOLUENE
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A production process for substituted phenylacetic acids or ester analogues thereof is disclosed. In this process toluene or toluene substituted with various substituents, an alcohol, an oxidant and carbon monoxide are used as raw materials to obtain compounds comprising structure of phenylacetic acid ester or analogues thereof by catalysis of the complex catalyst formed from transition metal and ligand, and such compounds are hydrolyzed to obtain various substituted phenylacetic acid based compounds. This type of compounds and their derivatives serve as important fine chemicals used widely in the industries of pharmaceuticals, pesticides, perfume and the like.
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Paragraph 0032; 0033
(2013/11/19)
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- Palladium-catalyzed oxidative carbonylation of benzylic C-H bonds via nondirected C(sp3)-H activation
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A new strategy for generating benzylpalladium reactive species from toluenes via nondirected C(sp3)-H activation has been developed. This led to construction of an efficient Pd-catalyzed reaction protocol for the oxidative carboxylation of benzylic C-H bonds to form substituted 2-phenylacetic acid esters and derivatives from inexpensive, commercially available starting materials.
- Xie, Pan,Xie, Yinjun,Qian, Bo,Zhou, Han,Xia, Chungu,Huang, Hanmin
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supporting information; experimental part
p. 9902 - 9905
(2012/08/08)
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- Pd-catalyzed decarboxylative cross-couplings of potassium malonate monoesters with aryl halides
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An efficient catalytic protocol for Pd-catalyzed decarboxylative cross-coupling of potassium malonate monoesters and derivatives with aryl bromides and chlorides are described. Because of its broad applicability, this new catalytic system provides an alternative method for the preparation of diverse aryl acetic acids and derivatives.
- Feng, Yi-Si,Wu, Wei,Xu, Zhong-Qiu,Li, Yan,Li, Ming,Xu, Hua-Jian
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p. 2113 - 2120
(2012/03/26)
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- Solvent-free esterification of carboxylic acids and alcohols in the presence of silphos [PCl3-n(SiO2)n] as a heterogeneous phosphine reagent
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An efficient solvent-free method for the preparation of esters from various aromatic and aliphatic acids with primary, secondary, and tertiary alcohols using a heterogeneous phosphine reagent, silphos [PCl3-n(SiO 2)n], in good yields is reported.
- Rao, Ambati Narasimha,Ganesan, Kumaran,Shinde, Chandra Kant
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experimental part
p. 2299 - 2308
(2012/06/18)
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- Alcoholysis of naturally occurring imides: Misleading interpretation of antifungal activities
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The frequent presence of the sulfur-containing amide penangin (10) in leaf extracts of Glycosmis species turned out to be the result of decomposition of imides generated by extraction and storage in MeOH. Reinvestigation of Glycosmis mauritiana and G. cf. puberula with acetone revealed the presence of six imides. In addition to penimides A (1) and B (2) and ritigalin (6), three new derivatives, krabin (4), isokrabin (5), and methoxypenimide B (3), were isolated and identified by spectroscopic methods. All six imides were shown to be susceptible to different rates of methanolic cleavage, leading to their corresponding methyl esters and sulfur-containing amides. Whereas the decomposition products penangin (10), isopenangin (11), and sinharin (14) are known, the corresponding cleavage of methyl N-methylthiocarbamate (7) from ritigalin (6), monitored in situ by 1H NMR spectroscopy, is described here for the first time. Its structure was further confirmed by GC-MS coupling. HPLC-UV comparison of many different samples of G. mauritiana, extracted with MeOH, revealed considerable chemical variations in sulfur-containing amides, strongly correlated with different antifungal potency. The lack of activity of many methanolic crude extracts can be explained by a preponderance of the inactive decomposition product penangin (10), whereas the corresponding naturally occurring imides penimides A (1) and B (2) and methoxypenimide B (3), extracted with acetone, showed high fungitoxic properties.
- Pacher, Thomas,Raninger, Adriane,Lorbeer, Eberhard,Brecker, Lothar,But, Paul Pui-Hay,Greger, Harald
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body text
p. 1389 - 1393
(2010/11/04)
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- Oxidation of substituted β-diketones with hydrogen peroxide: Synthesis of esters through the formation of bridged 1,2,4,5-tetraoxanes
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Acid-catalyzed oxidation of alkyl- and benzyl-substituted -diketones by hydrogen peroxide at 79-120C in a mixture of an alcohol and a strong acid (sulfuric acid, tetrafluoroboric acid, or perchloric acid) gave the corresponding esters through the formation of bridged 1,2,4,5-tetraoxanes. Georg Thieme Verlag Stuttgart · New York.
- Terentev, Alexander O.,Borisov, Dmitry A.,Yaremenko, Ivan A.,Ogibin, Yuri N.,Nikishin, Gennady I.
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experimental part
p. 1145 - 1149
(2010/06/14)
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- The effect of substituents and operating conditions on the electrochemical fluorination of alkyl phenylacetates in Et3N·4HF medium
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Selective electrochemical fluorination of alkyl phenylacetates (Ph-CH2-COOR, where R is methyl, ethyl, n-propyl, n-butyl, i-propyl and sec-butyl) under galvanostatic conditions were reported in Et3N·4HF medium. Preparative electrolysis experiments were carried out both in pre-electrolysed dry Et3N·4HF and the same electrolyte medium without pre-electrolysis. Very little hydrolysed fluorinated products were obtained in pre-electrolysed medium where as significant quantities of hydrolysed products leading to fluorinated phenylacetic acid were obtained from Et3N·4HF without pre-electrolysis. Under optimum experimental conditions up to 87% selectivity of monofluoro ester could be achieved. Difluoro alkyl phenylacetate, monofluoro and difluoro phenylacetic acids were the other predominant side products obtained. The hydrolysis appears to be initiated by tautomeric transformation of proton after the initial electro oxidative formation of the cation radical. 19F as well as 1H NMR spectroscopy have been employed to identify the minor constituents formed during the electro oxidative process.
- Ilayaraja,Manivel,Velayutham,Noel
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p. 185 - 192
(2008/09/17)
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- An efficient use of zeolite catalysts for esterification of carboxylic acids
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A mild and practical method (batch process) for the esterification of carboxylic acids with alcohols using zeolite catalysts in good to excellent yields is described. The esterification of phenylacetic acid with ethanol has also been carried out in very high yield using continuous flow fixed bed reactor.
- Gumaste, Vikas K.,Deshmukh,Bhawal
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p. 1174 - 1179
(2007/10/03)
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- Oxidation of Alkynes by Hydrogen Peroxide Catalyzed by Methylrhenium Trioxide
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The oxidation of alkynes with hydrogen peroxide is catalyzed by methylrhenium tioxide.The reactions can be rationalized by postulating that an oxirene intermediate is formed between a rhenium peroxide and the alkyne.Internal alkynes yield α-diketones and carboxylic acids, the latter from the complete cleavage of the triple bonds.Rearrangement products were observed only for aliphatic alkynes.Terminal alkynes gave carboxylic acids and their derivatives and α-keto acids as the major products, but their yields varied with the solvent used.
- Zhu, Zuolin,Espenson, James H.
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p. 7728 - 7732
(2007/10/03)
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- A facile conversion of halides, alcohols and olefins to esters using iron(III) perchlorate
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A facile method has been developed for the esterification of halides/alcohols/olefins with carboxylic acids using iron(III) perchlorate.
- Kumar,Kumar,Parmar
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p. 1087 - 1094
(2007/10/02)
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- Transesterification of methyl arylacetates wtih lithium alkoxides
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A series of methyl arylacetates were transesterified in excellent yields using lithium alkoxides derived from primary, secondary, and tertiary aliphatic alcohols, benzyl alcohols, and allyl alcohol.
- Bhawal,Khanapure,Biehl
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p. 112 - 114
(2007/10/02)
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- STRUCTURAL EFFECT ON THE MECHANISTIC PATHWAY OF THE DECOMPOSITION OF 3-ALKYL-1-ARYLTRIAZENES: A KINETIC STUDY
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A kinetic study of the reaction between 3-alkyl-1-aryltriazenes and substituted acetic acids has been made in solvent acetone over the temperature range 21-37 deg C.Ea is 17.3 +/- 0.3 kcal mol-1 and log A is 10.3 +/- 0.1.Influence of the substituents on the reaction rate has been analyzed.The Hammett correlation with ? gave a ρ value of -0.96 for para-aryl substituted triazenes and +0.35 for meta- and para-substituted phenylacetic acid.The rate of decomposition of triazenes is also affected by changing the alkyl group.From these results a duality in mechanism is proposed; first, a simultaneous protonation and alkyl group expulsion to be the rate-determining step when R is tertiary, benzylic and possibly secondary.Secondly, a concerted mechanism for the protonation of nitrogen and cleavage of the N-R bond for primary alkyl groups.
- Laila, Abdulhameed A. R.
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p. 453 - 456
(2007/10/02)
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- CATALYTIC ROLE OF DIORGANOTIN DICHLORIDE IN ESTERIFICATION OF CARBOXYLIC ACIDS
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Various carboxylic acids were converted into corresponding esters in fair to good yields by diorganotin dichloride-catalysed reaction with alcohols.
- Kumar, Amal K.,Chattopadhyay, Tapas K.
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p. 3713 - 3714
(2007/10/02)
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- Manufacture of arylacetic acids and their esters
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Arylacetic acids and their esters, of the formula Ar(CH2 -COOR)n (where Ar=aryl, R is H or a hydrocarbon radical, and n is 1 or 2) are manufactured by carbonylation of halomethylaryl compounds Ar(CH2 C)n (where X is Cl, Br or I) with carbon monoxide and a catalyst m+ ?Fe(O)3 NO!- (where M is an alkali metal, ammonium or one equivalent of an alkaline earth metal) in the presence of stoichiometric amounts of an inorganic base or of an alcoholate of an alcohol ROH.
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- SYNTHESIS OF ESTERS BY RHODIUM(I) CATALYZED BORATE ESTER-BENZYLIC BROMIDE CARBONYLATION REACTIONS
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Benzylic halides react with trialkylborates and carbon monoxide, in the presence of 1,5-hexadienerhodium chloride dimer, to give esters in excellent yields.The reaction is applicable to the synthesis of primary, secondary and even tertiary esters.
- Woell, James B.,Alper, Howard
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p. 3791 - 3794
(2007/10/02)
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