- A solvent-reagent selection guide for Steglich-type esterification of carboxylic acids
-
The Steglich esterification is a widely employed method for the formation of esters under mild conditions. A number of issues regarding the sustainability of this transformation have been identified, chiefly the use of hazardous carbodiimide coupling reagents in conjunction with solvents with considerable issues such as dichloromethane (DCM) and N,N-dimethylformamide (DMF). To overcome these issues, we have developed a solvent-reagent selection guide for the formation of esters via Steglich-type reactions with the aim of providing safer, more sustainable conditions. Optimum reaction conditions have been identified after high-throughput screening of solvent-reagent combinations, namely the use of Mukaiyama's reagent (Muk) in conjunction with solvent dimethyl carbonate (DMC). The new reaction conditions were also exemplified through the synthesis of a small selection of building-block like molecules and includes the formation of t-butyl esters.
- Jordan, Andrew,Sneddon, Helen F.,Sydenham, Jack,Whymark, Kyran D.
-
supporting information
p. 6405 - 6413
(2021/09/10)
-
- Photoinduced Diverse Reactivity of Diazo Compounds with Nitrosoarenes
-
A diverse reactivity of diazo compounds with nitrosoarene in an oxygen-transfer process and a formal [2 + 2] cycloaddition is reported. Nitosoarene has been exploited as a mild oxygen source to oxidize an in situ generated carbene intermediate under visible-light irradiation. UV-light-mediated in situ generated ketenes react with nitosoarenes to deliver oxazetidine derivatives. These operationally simple processes exemplify a transition-metal-free and catalyst-free protocol to give structurally diverse α-ketoesters or oxazetidines.
- Roy, Sourav,Kumar, Gourav,Chatterjee, Indranil
-
supporting information
p. 6709 - 6713
(2021/09/08)
-
- Room Temperature Coupling of Aryldiazoacetates with Boronic Acids Enhanced by Blue Light Irradiation
-
A visible-light-promoted photochemical protocol is reported for the coupling of aryldiazoacetates with boronic acids. This photochemical reaction shows great enhancement compared to the same protocol performed in the absence of light. Except for a few cases, the room temperature coupling in the dark (thermal process) generally does not work. When it does, it is likely to also involve free carbenes as key intermediates. Alternatively, photochemical reactions show a broad scope, can be performed under air and tolerate a wide variety of functional groups. Reaction-evolution monitoring, DFT calculations and control experiments have been used to evaluate the main aspects of this intricate mechanistic scenario. Biologically active molecules Adiphenine, Benactyzine and Aprophen have been prepared as examples of synthetic applications.
- da Silva, Amanda F.,Afonso, Marco A. S.,Cormanich, Rodrigo A.,Jurberg, Igor D.
-
supporting information
p. 5648 - 5653
(2020/04/22)
-
- PHOSPHINIC AMIDE PRODRUGS OF TENOFOVIR
-
Compounds of Formula I: I and their pharmaceutically acceptable salts are useful for the inhibition of HIV reverse transcriptase. The compounds may also be useful for the prophylaxis or treatment of infection by HIV and in the prophylaxis, delay in the onset or progression, and treatment of AIDS. The compounds and their salts can be employed as ingredients in pharmaceutical compositions, optionally in combination with other antiviral agents, immunomodulators, antibiotics or vaccines.
- -
-
Page/Page column 38
(2020/02/14)
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- Preparation of Organic Nitrates from Aryldiazoacetates and Fe(NO3)3·9H2O
-
A thermal protocol is reported for the formal insertion of nitric acid into aryldiazoacetates using Fe(NO3)3·9H2O. This strategy is mild and high yielding and allows the preparation of a large variety of members of an unprecedented family of organic nitrates. The nitrate group can be also readily transformed into other functional groups and heterocyclic moieties and can possibly allow new biological explorations of untapped potential associated with their NO-releasing ability.
- Thurow, Samuel,Fernandes, Alessandra A. G.,Quevedo-Acosta, Yovanny,De Oliveira, Matheus F.,De Oliveira, Marcelo G.,Jurberg, Igor D.
-
supporting information
p. 6909 - 6913
(2019/09/12)
-
- Carbon monoxide is used as a source of halogen compound heterogeneous palladium catalyst in the presence of the aldehyde carbonyl compound by reaction carbonylation method (by machine translation)
-
[Problem] catalyst and the presence of carbon monoxide, the halogen compound is a carbonyl compound in the carbonylation reaction, catalysts or carbon monoxide source technique has problems. [Solution] the presence of the catalyst and the carbon monoxide, the halogen compound is carbonylation reaction method for producing a carbonyl compound, As a heterogeneous palladium catalyst, carbon monoxide is produced from an aldehyde carbonyl compound used in the method. [Drawing] no (by machine translation)
- -
-
Paragraph 0067; 0078; 0079; 0080
(2018/04/06)
-
- Synthesis and characterization of stable ZnO nanoparticles using imidazolium-based ionic liquids and their applications in esterification reaction
-
ZnO nanoparticles have been synthesized from zinc acetate using 1-octyl-3-methylimidazolium hexafluorophosphate as capping agent under microwave irradiation condition in a very short period of time and characterized using UV-visible spectroscopy, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-TPD analysis. The ZnO NPs have been used as a solid reusable acid catalyst for esterification of carboxylic acids with alcohols.
- Kavya,Vijaya Kumar,Ramesh Kumar
-
p. 1112 - 1120
(2018/09/21)
-
- [Co(MeTAA)] Metalloradical Catalytic Route to Ketenes via Carbonylation of Carbene Radicals
-
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
-
supporting information
p. 2251 - 2258
(2018/04/09)
-
- Ni-Catalyzed chemoselective alcoholysis of: N -acyloxazolidinones
-
Although N-acyloxazolidinone-based (catalytic) asymmetric synthetic methodologies occupy an important position in modern organic synthesis, the catalytic cleavage of a chiral auxiliary remains underdeveloped. We report the Ni(cod)2/bipyr.-catalyzed alcoholysis of N-acyloxazolidinones to deliver esters. The reaction is broad in scope for both N-acyloxazolidinone substrates and alcohol nucleophiles, and displays good functional group tolerance and excellent chemoselectivity. A gram-scale methanolysis allowed the enantioselective synthesis of the C22-C26 segment of a close analogue of the potent immunosuppressant agent FK506.
- Huang, Pei-Qiang,Geng, Hui
-
supporting information
p. 593 - 599
(2018/02/14)
-
- Cation-Controlled Enantioselective and Diastereoselective Synthesis of Indolines: An Autoinductive Phase-Transfer Initiated 5-endo-trig Process
-
A catalytic enantioselective approach to the synthesis of indolines bearing two asymmetric centers, one of which is all-carbon and quaternary, is described. This reaction proceeds with high levels of diastereoselectivity (>20:1) and high levels of enantioselectivity (up to 99.5:0.5 er) in the presence of CsOH·H2O and a quinine-derived ammonium salt. The reaction most likely proceeds via a delocalized 2-aza-pentadienyl anion that cyclizes either by a suprafacial electrocyclic mechanism, or through a kinetically controlled 5-endo-trig Mannich process. Density functional theory calculations are used to probe these two mechanistic pathways and lead to the conclusion that a nonpericyclic mechanism is most probable. The base-catalyzed interconversion of diastereoisomeric indolines in the presence of certain quaternary ammonium catalysts is observed; this may be rationalized as a cycloreversion-cyclization process. Mechanistic investigations have demonstrated that the reaction is initiated via a Makosza-like interfacial process, and kinetic analysis has shown that the reaction possesses a significant induction period consistent with autoinduction. A zwitterionic quinine-derived entity generated by deprotonation of an ammonium salt with the anionic reaction product is identified as a key catalytic species and the role that protonation plays in the enantioselective process outlined. We also propose that the reaction subsequently occurs entirely within the organic phase. Consequently, the reaction may be better described as a phase-transfer-initiated rather than a phase-transfer-catalyzed process; this observation may have implications for mechanistic pathways followed by other phase-transfer-mediated reactions.
- Sharma, Krishna,Wolstenhulme, Jamie R.,Painter, Phillip P.,Yeo, David,Grande-Carmona, Francisca,Johnston, Craig P.,Tantillo, Dean J.,Smith, Martin D.
-
supporting information
p. 13414 - 13424
(2015/11/09)
-
- LED lighting as a simple, inexpensive, and sustainable alternative for Wolff rearrangements
-
The Wolff rearrangement is one of the best methods for chain homologation. However, it still suffers from many drawbacks with respect to its practical execution in the laboratory. We wish to demonstrate the use of commercial LED lamps as a sustainable alternative for the classic experimental protocols typically used for Wolff rearrangements. This journal is
- Bernardim, Barbara,Hardman-Baldwin, Andrea M.,Burtoloso, Antonio C. B.
-
p. 13311 - 13314
(2015/02/19)
-
- Transformation of amides into esters by the use of chlorotrimethylsilane
-
A mild transformation of various amides and imides into the corresponding esters and diesters in good yields by using chlorotrimethylsilane and alcohols at rt are described. Either primary, secondary, or tertiary amide or imide can be used in this transformation. Primary and secondary alcohols gave better yields than tertiary alcohols.
- Xue, Cuihua,Luo, Fen-Tair
-
p. 359 - 362
(2015/02/02)
-
- Efficient microwave-assisted esterification reaction employing methanesulfonic acid supported on alumina as catalyst
-
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
-
p. 2386 - 2392
(2014/07/22)
-
- Ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o -NosylOXY): A recyclable coupling reagent for racemization-free synthesis of peptide, amide, hydroxamate, and ester
-
Ubiquitousness of amide and ester functionality makes coupling reactions extremely important. Although numerous coupling reagents are available, methods of preparation of the common and efficient reagents are cumbersome. Those reagents generate a substantial amount of chemical waste and lack recyclability. Ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o-NosylOXY), the first member of a new generation of coupling reagents, produces byproducts that can be easily recovered and reused for the synthesis of the same reagent, making the method more environmentally friendly and cost-effective. The synthesis of amides, hydroxamates, peptides, and esters using this reagent is described. The synthesis of the difficult sequences, for example, the islet amyloid polypeptide (22-27) fragment (with a C-terminal Gly, H-Asn-Phe-Gly-Ala-Ile-Leu-Gly-NH 2) and acyl carrier protein (65-74) fragment (H-Val-Gln-Ala-Ala-Ile- Asp-Tyr-Ile-Asn-Gly-OH), following the solid-phase peptide synthesis (SPPS) protocol and Amyloid β (39-42) peptide (Boc-Val-Val-IIe-Ala-OMe), following solution-phase strategy is demonstrated. Remarkable improvement is noticed with respect to reaction time, yield, and retention of stereochemistry. A mechanistic investigation and recyclability are also described.
- Dev, Dharm,Palakurthy, Nani Babu,Thalluri, Kishore,Chandra, Jyoti,Mandal, Bhubaneswar
-
p. 5420 - 5431
(2014/07/08)
-
- Ethyl 2-(tert-butoxycarbonyloxyimino)-2-cyanoacetate (Boc-Oxyma) as coupling reagent for racemization-free esterification, thioesterification, amidation and peptide synthesis
-
Here we report the synthesis and utility of ethyl 2-(tert- butoxycarbonyloxyimino)-2-cyanoacetate (Boc-Oxyma) as an efficient coupling reagent for racemization-free esterification, thioesterification, amidation reactions and peptide synthesis that uses equimolar amounts of acids and alcohols, thiols, amines or amino acids, respectively. Its application to solid phase as well as solution phase peptide synthesis is also demonstrated and a mechanistic investigation is discussed. Boc-Oxyma is similar to the well known coupling agent COMU {1-[1-cyano-2-ethoxy-2-oxoethylideneaminooxy)- dimethylaminomorpholino] uronium hexafluorophosphate} in terms of its high reactivity and mechanism of action. However, it is not only much easier to prepare, but also to recover and reuse, thereby generating far less chemical waste.
- Thalluri, Kishore,Nadimpally, Krishna Chaitanya,Chakravarty, Maharishi Parasar,Paul, Ashim,Mandal, Bhubaneswar
-
supporting information
p. 448 - 462
(2013/05/09)
-
- PROCESS FOR SYNTHESIZING PHENYLACETIC ACID BY CARBONYLATION OF TOLUENE
-
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.
- -
-
Paragraph 0034; 0035
(2013/11/19)
-
- An indium-mediated allylative/transesterification DFT-directed approach to chiral C(3)-functionalized phthalides
-
A one-pot synthesis of chiral C(3)-substituted phthalides via an indium-mediated allylation/transesterification reaction is described. The development of this reaction was facilitated through the applied use of DFT calculations to rationalize the stereoselection of a chiral In-mediated process. It was discovered that the enantiomeric excess of this reaction depended upon the steric size, chain length, and substitution of the aldehyde employed.
- Mirabdolbaghi, Roya,Dudding, Travis
-
supporting information; experimental part
p. 3748 - 3751
(2012/09/07)
-
- Palladium-catalyzed oxidative carbonylation of benzylic C-H bonds via nondirected C(sp3)-H activation
-
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
-
supporting information; experimental part
p. 9902 - 9905
(2012/08/08)
-
- Pd-catalyzed decarboxylative cross-couplings of potassium malonate monoesters with aryl halides
-
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
-
p. 2113 - 2120
(2012/03/26)
-
- Reduction of carboxylic acids using esters of benzotriazole as high-reactivity intermediates
-
Herein, we describe a simple and practical protocol for the reduction of carboxylic acids via the in situ formation of hydroxybenzotriazole esters followed by reaction with sodium borohydride to give the corresponding alcohols. The reaction proceeds with excellent yields in the presence of water. Georg Thieme Verlag Stuttgart - New York.
- Morales-Serna, Jose Antonio,Garcia-Rios, Erendira,Bernal, Jorge,Paleo, Ehecatl,Gavino, Ruben,Cardenas, Jorge
-
scheme or table
p. 1375 - 1382
(2011/06/19)
-
- Alcoholysis of naturally occurring imides: Misleading interpretation of antifungal activities
-
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
-
body text
p. 1389 - 1393
(2010/11/04)
-
- A simple procedure for the esterification of alcohols with sodium carboxylate salts using 1-tosylimidazole (TsIm)
-
An efficient and selective method for esterification of alcohols using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, alcohols are refluxed with a mixture of RCO2Na (R: alkyl and aryl), TsIm, and triethylamine in the presence of catalytic amounts of tetra-n-butylammonium iodide (TBAI) in DMF to afford the corresponding esters in good yields. This methodology is highly efficient for various structurally diverse alcohols with selectivity for ROH: 1° > 2° > 3°.
- Soltani Rad, Mohammad Navid,Behrouz, Somayeh,Faghihi, Mohammad Ali,Khalafi-Nezhad, Ali
-
p. 1115 - 1120
(2008/09/17)
-
- Transesterifications mediated by t-BuNH2
-
A mild protocol for transesterification of simple esters is described. The method is based on the use of t-BuNH2/ROH (R = Me, Et, i-Pr, t-Bu) with or without LiBr. The scope of the procedure was explored for aliphatic and aromatic esters. The protocol is particularly useful when going from higher to lower hindered esters and harsh reaction conditions are needed for the reversal process. A rationalization of the mechanism is presented. The scope and limitation of this transformation are also described.
- Suárez-Castillo, Oscar R.,Montiel-Ortega, Luis Alberto,Fragoso-Vázquez, Manuel Jonathan,Meléndez-Rodríguez, Myriam,Sánchez-Zavala, Maricruz
-
p. 996 - 999
(2008/09/17)
-
- The effect of substituents and operating conditions on the electrochemical fluorination of alkyl phenylacetates in Et3N·4HF medium
-
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
-
p. 185 - 192
(2008/09/17)
-
- A fast and simple method for the acylation of alcohols with acid chlorides promoted by metallic samarium
-
Acylation of primary, secondary, allyl and benzyl alcohols with acid chlorides promoted by samarium metal under neutral condition gave carboxylic acid esters in good to excellent yields. Acylation of a tertiary alcohol did not occur under the same reaction conditions.
- Jia, Xue-Shun,Wang, Hai-Long,Huang, Qing,Kong, Ling-Long,Zhang, Wei-He
-
p. 135 - 138
(2007/10/03)
-
- 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)
-
- Transformation of amides into esters by the use of chlorotrimethylsilane
-
A mild transformation of various amides and imides into the corresponding esters and diesters in good yields by using chlorotrimethylsilane and alcohols at rt are described. Either primary, secondary, or tertiary amide or imide can be used in this transformation. Primary and secondary alcohols gave better yields than tertiary alcohols.
- Xue, Cuihua,Luo, Fen-Tair
-
p. 359 - 362
(2007/10/03)
-
- Acylation and alkoxycarbonylation of benzoxazoline-2-thione and benzothiazoline-2-thione
-
Acylation of benzoxazoline-2-thione (1) and benzothiazoline-2-thione (2) with acetic anhydride (3) and acyl chlorides (4) gave N-acyl (5, 6) and/or S-acyl (7, 8) derivatives depending on the nature of acylating agents and bases used. Alkoxycarbonylation of 1 with aralkyl chlorocarbonates (9) gave N-alkoxycarbonyl derivatives (10) mainly, while that of 2 with aralkyl chloroccarbonates (9) gave S-alkoxycarbonyl derivatives (12) exclusively. Photolysis of N-acyl derivatives (5 or 6) in the presence of alcohols afforded 1 or 2, respectively, together with esters (16).
- Nishio, Takehiko,Shiwa, Kiyoko
-
p. 313 - 324
(2007/10/03)
-
- Efficient photolytic esterification of carboxylic acids with alcohols in perhalogenated methane
-
Condensation of carboxylic acids and alcohols to give esters was accomplished with selectivity under photolytic conditions in 66-99% yields by use of CCl4 or BrCCl3 at room temperature.
- Hwu, Jih Ru,Hsu, Chuan-Yi,Jain, Moti L.
-
p. 5151 - 5154
(2007/10/03)
-
- Na2CO3/SOCl2: A mild and convenient reagent for the preparation of isopropyl carboxylates
-
Na2CO3/SOCl2 has been used for esterification of aliphatic and aromatic acids with isopropanol. This esterification method is compatible with a wide assortment of functional groups.
- Kazemi, Foad,Kiasat, Ali Reza,Mombaini, Began
-
p. 1187 - 1191
(2007/10/03)
-
- Silica Chloride: A Versatile Heterogeneous Catalyst for Esterification and Transesterification
-
Silica chloride has been found to be an efficient catalyst for esterification of carboxylic acids (aliphatic, aromatic and conjugated) with alcohols (primary, secondary and tertiary) as well as for transesterification of esters (by both alcoholysis and acidolysis).
- Srinivas,Mahender,Das, Biswanath
-
p. 2479 - 2482
(2007/10/03)
-
- A Simple and Efficient Esterification Method
-
A convenient and practical esterification was realized and this reaction proceeded without a dehydrating reagent or water removal equipment. The synthesis of esters by reaction of carboxylic acids with various alcohols such as methyl, ethyl, isopropyl, isobutyl, allyl, benzyl, propargyl and decanyl alcohols were achieved with a catalytic amount of CBr4 under refluxing reaction condition.
- Ming-Yi, Chen,Lee, Adam Shih-Yuan
-
p. 103 - 108
(2007/10/03)
-
- Esterification of carboxylic acids with alcohols under microwave irradiation in the presence of zinc triflatet
-
The esterification of aliphatic and aromatic carboxylic acids with various alcohols (1°, 2°, 3°, benzylic) was studied under microwave irradiation in the presence of zinc triflate as catalyst; the reaction times were short and the yield of reactions was good to excellent.
- Shekarriz, Marzieh,Taghipoor, Sohrab,Khalili, Ali Asghar,Jamarani, Mohammad Soleymani
-
p. 172 - 173
(2007/10/03)
-
- Improved Cs2CO3 promoted O-alkylation of acids
-
Cesium carbonate mediated O-alkylation of carboxylic acids was efficiently carried out under mild in situ conditions to give the corresponding esters exclusively. Chiral templates including α-hydroxy and α-alkoxy acids were also converted to their corresponding esters with no observed racemization.
- Parrish, Jay P.,Dueno, Eric E.,Kim, Seok-In,Jung, Kyung Woon
-
p. 2687 - 2700
(2007/10/03)
-
- Esterification in dry media using ferric perchlorate adsorbed on silica gel
-
Adsorption of Fe(ClO4)3(H2O)6 onto chromatographic grade silica gel in the presence of alcohol ( to be used for esterification ) produces a supported reagent, Fe(ClO4)3(ROH)6/SiO2. This reagent, has been found effective for the rapid and high yield of esters, on grinding in the presence of carboxylic acids using pestle and mortar in the solid state.
- Parmar, Anupama,Kaur, Jatinder,Goyal, Rita,Kumar, Baldev,Kumar, Harish
-
p. 2821 - 2826
(2007/10/03)
-
- Simple transformation of nitrile into ester by the use of chlorotrimethylsilane
-
Treatment of nitriles with alcohol and chlorotrimethylsilane at 50°C for 4 h could give esters in fair to good yields. Under similar reaction conditions, intramolecular lactonization via the concomitant nitrile and hydroxy groups in good yield were also demonstrated.
- Luo, Fen-Tair,Jeevanandam, Arumugasamy
-
p. 9455 - 9456
(2007/10/03)
-
- Ligand exchange reaction of sulfoxides in organic synthesis: A versatile procedure for one-carbon homologation of methylesters to esters, thioesters, carboxylic acids and amides
-
A novel two-step procedure for one-carbon homologation of methylesters to esters, thioesters, carboxylic acids and amides is described. Methylesters are reacted with lithium carbanion of chloromethyl phenyl sulfoxide to give α-chloro α-sulfinyl ketones in 70 to 90% yields. Potassium enolate of the α-chloro α-sulfinyl ketone was treated with tert-butyllithium at -78°C to give alkynolate via alkylidene carbenoid. This intermediate was treated with alcohols, thioles, 5% aqueous NaOH, and amine hydrochlorides to afford one-carbon homologated esters, thioesters, carboxylic acids and amides, respectively, in good to excellent yields.
- Satoh, Tsuyoshi,Unno, Hideaki,Mizu, Yasuhiro,Hayashi, Yasumasa
-
p. 7843 - 7854
(2007/10/03)
-
- An efficient use of zeolite catalysts for esterification of carboxylic acids
-
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
-
p. 1174 - 1179
(2007/10/03)
-
- Mild hydrolysis or alcoholysis of amides. Ti(IV) catalyzed conversion of primary carboxamides to carboxylic acids or esters
-
Reaction of primary amides (e.g., 1a or 6-13) or O-methylhydroxamates (1b and 1c) with a catalytic amount of TiCI4 and one equivalent of aqueous HCI converts these compounds in good yields to carboxylic esters (when an alcohol is used as solvent) or to carboxylic acids (when 9:1 dioxane:H2O is used as solvent). These conversions are chemoselective for primary amides: mono- and dialkyl amides are not affected by the reaction conditions. The hydrolysis conditions described do not compromise the stereochemical integrity of an adjacent chiral center. This is exemplified by the hydrolysis of naproxen amide (34) to naproxen (33) without detectable racemization as determined by chiral HPLC.
- Fisher,Caroon,Stabler,Lundberg,Zaidi,Sorensen,Sparacino,Muchowski
-
p. 142 - 145
(2007/10/02)
-
- Structure-Activity Relationships in the Esterase-catalysed Hydrolysis and Transesterification of Esters and Lactones
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The Broensted exponents for the alkaline hydrolysis of alkyl esters are 1.3 and 0.4 for substitution in the acyl and alcohol portions, respectively, which is indicative of a transition state which resembles the anionic tetrahedral intermediate with a localised negative charge.By contrast, the rate of the pig liver esterase (PLE)-catalysed hydrolysis shows little dependence upon the electron-withdrawing power of substituents.The values of kcat are independent of the pKa of the leaving group alcohol suggesting rate-limiting deacylation.There is a small steric effect of α-substitution in both the alcohol and carboxylic acid residues for the enzyme-catalysed reactions but the enzyme rate enhancement factor remains high for most esters.There is no substantial ee observed for the hydrolysis of racemic esters although the kinetic data can be used for determining the regioselective hydrolysis of diesters.Unsubstituted lactones are poor substrates for PLE but derivatives with hydrophobic substituents show kcat/Km values similar to those for acyclic esters.Dihydrocoumarin undergoes transesterification catalysed by PLE, kcat increases with increasing alcohol concentration indicative of rate-limiting deacylation.There is enantioselectivity in the PLE-catalysed hydrolysis of some racemic lactones but little or none in the transesterification of racemic alcohols with dihydrocoumarin.
- Barton, Patrick,Laws, Andrew P.,Page, Michael I.
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p. 2021 - 2030
(2007/10/02)
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- Transesterifications with 1,8-Diazabicycloundec-7-ene/Lithium Bromide (DBU/LiBr) - Also Applicable to Cleavage of Peptides from Resins in Merrifield Syntheses
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A mixture of the amidine base 1,8-diazabicycloundec-7-ene (DBU) and LiBr (preferably 0.5 and 5 equiv., resp.) turns out to be a highly efficient catalyst (at 0-25 deg C) for saponifications (in THF/H2O) and transesterifications (in ROH).The scope and limitations of the method are determined using ca. two dozens of different ester/alcohol combinations (Schemes 2 and 3).The investigation is focused on peptides as substrates.Under carefully controlled conditions, no epimerization occurs with N-Boc- and N-Z-protected peptide esters, when methyl, ethyl, isopropyl, or allyl esters are the products, as shown for peptides containing up to six amino acids, with Ala, Leu, MeLeu, Asp(OEt), or Tyr at the C-terminus (Scheme 3 and Tables 1 and 2).Hydrolytic and transesterifying detachments of Boc-Leu-Ala-Gly-Val-OR and Boc-Leu-Ala-Gly-Phe-OR (R = H, Me) from PAM and Wang resins (1-8 h at 0-25 deg C, 2 equiv. of DBU, 5 equiv. of LiBr) can be achieved by this method without epimerization of the C-terminal stereogenic center; a comparison with other methods (HF, Ti(OR)4) is given (Schemes 4 and 5).Possible protecting-group strategies involving the DBU/LiBr method are discussed (Table 3).Extensive experimental details are given.
- Seebach, Dieter,Thaler, Adrian,Blaser, Denis,Ko, Soo Y.
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p. 1102 - 1118
(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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- A novel and versatile route to mixed p-toluenesulphonic carboxylic anhydrides
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A versatile route to the mixed p-toluenesulphonic carboxylic anhydrides (1) via the reaction of tetra-n-butylammonium carboxylate (2) with p-toluenesulphonyl chloride in a neutral medium is described.Some of the synthetic applications of the proposed method are described.
- Kumar, Arvind,Srivastava, Nivedita,Mital, Alka
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p. 606 - 607
(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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- DI-2-PYRIDYL CARBONATE: A NEW EFFICIENT COUPLING AGENT FOR THE DIRECT ESTERIFICATION OF CARBOXYLIC ACIDS
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Reaction of carboxylic acids with equimolar amounts of di-2-pyridyl carbonate and alcohols or thiols in the presence of 4-dimethylaminopyridine as a catalyst in methylene chloride at room temperature affords the corresponding esters in high yields under mild conditions.
- Kim, Sunggak,Lee, Jae In,Ko, Young Kwan
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p. 4943 - 4946
(2007/10/02)
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- Synthesis of phenylacetic acid esters
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Esters of phenylacetic acids are prepared in a single step by hydrolysis of 2,2,2-trichloro-1-phenylethanes in inorganic basic media.
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