Direct Condensation Of Carboxylic Acids Research Articles

Microwave-Assisted Synthesis of 5-Substituted 3-Amino-1,2,4-triazoles from Aminoguanidine Bicarbonate and Carboxylic Acids

The effect of the molar ratio between reagents, reaction time and temperature on the yield of 5-substituted 3-amino-1,2,4-triazoles obtained by the direct condensation of carboxylic acids with aminoguanidine bicarbonate under acid catalysis conditions was studied. As a result, a general green straightforward synthesis of the title compounds bearing aliphatic substituents or a phenyl ring was developed using sealed reaction vials under controlled microwave synthesis conditions that are suitable for the application of volatile starting carboxylic acids. Our straightforward synthetic method proposed in this work increases the synthetic accessibility of these widely used building blocks and therefore is able to significantly expand the structural diversity of compounds containing a triazole moiety for the needs of drug discovery.

Synthesis of benzamides through direct condensation of carboxylic acids and amines in the presence of diatomite earth@IL/ZrCl4 under ultrasonic irradiation

A green, rapid, mild and highly efficient pathway for the preparation of benzamide derivatives is reported. The reaction was performed through direct condensation of benzoic acids and amines under ultrasonic irradiation in the presence of Lewis acidic ionic liquid immobilized on diatomite earth (diatomite earth@IL/ZrCl4). A new, highly efficient and green solid acid catalyst was easily prepared via a two-step procedure and used as an effective reusable catalyst. The prepared catalyst provides active sites for the synthesis of benzamides. The advantages of this method are the use of a superior and recoverable catalyst, low reaction times, simple procedure, high-yielding and eco-friendly process and use of ultrasonic irradiation as a green and powerful technology. Since benzamides are used widely in the pharmaceutical, paper and plastic industries, and also as an intermediate product in the synthesis of therapeutic agents, the presented new synthetic methods for this type of compounds can be of considerable importance.

Formation of amides: one-pot condensation of carboxylic acids and amines mediated by TiCl4

A general procedure for the synthesis of amides via the direct condensation of carboxylic acids and amines in the presence of TiCl4 is reported. The amidation reaction was performed in pyridine at 85 °C with a wide range of substrates providing the corresponding amide products in moderate to excellent yields and high purity. The reaction proceeds with low yields when both the carboxylic acid and the amine are sterically hindered. The process takes place with nearly complete preservation of the stereochemical integrity of chiral substrates.

Catalytic amide formation from non-activated carboxylic acids and amines

The amide functionality is found in a wide variety of biological and synthetic structures such as proteins, polymers, pesticides and pharmaceuticals. Due to the fact that synthetic amides are still mainly produced by the aid of coupling reagents with poor atom-economy, the direct catalytic formation of amides from carboxylic acids and amines has become a field of emerging importance. A general, efficient and selective catalytic method for this transformation would meet well with the increasing demands for green chemistry procedures. This review covers catalytic and synthetically relevant methods for direct condensation of carboxylic acids and amines. A comprehensive overview of homogeneous and heterogeneous catalytic methods is presented, covering biocatalysts, Lewis acid catalysts based on boron and metals as well an assortment of other types of catalysts.

Direct Esterification of Carboxylic Acids with Alcohols Catalyzed by Iron(III) Acetylacetonate Complex

Direct condensation of carboxylic acids and alcohols with electronic, steric, and functional group variations was carried out using the environmentally benign, moisture-stable, inexpensive, and recoverable iron(III) acetylacetonate [Fe(acac)3] as catalyst (5 mol%). This iron salt efficiently catalyzed the esterification of several primary and secondary alcohols in refluxing xylene, without the need for a dehydration reagent. The chemoselectivity of the proposed protocol was demonstrated by the selective esterification of primary alcohol functionality in racemic 1-phenylethane-1,2-diol with benzoic acid. The esterification was also applicable to unmasked α -hydroxyacid, guasiaromatic, heterocyclic, and N-protected amino acids. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

ChemInform Abstract: Boric Acid‐Catalyzed Direct Condensation of Carboxylic Acids with Benzene‐1,2‐diamine into Benzimidazoles.

AbstractDirect cyclocondensation of o‐phenylenediamine (I) with a variety of carboxylic acids is readily achieved using catalytic amounts of boric acid in refluxing toluene under Dean‐Stark conditions.

Boric Acid‐Catalyzed Direct Condensation of Carboxylic Acids with Benzene‐1,2‐diamine into Benzimidazoles

AbstractThe applicability of boric acid catalysis for the direct condensation of carboxylic acids with benzene‐1,2‐diamine to give 2‐substituted benzimidazoles was investigated. It was found that catalytic amounts (5–10 mol‐%) of boric acid efficiently promote the cyclocondensation of aliphatic carboxylic acids in refluxing toluene. In addition, the relatively neutral conditions allow the use of acid‐sensitive substrates and give rise to specific transformations and selectivities that are not observed with some classical methods. Benzoic acids were found to be less reactive than aliphatic acids and thus require refluxing xylene for better efficiency. Phenylboronic acid was found to be inactive as a catalyst due to its rapid consumption by condensation with benzene‐1,2‐diamine to give a 2‐phenylbenzodiazaborole.

Zirconyl Chloride: An Efficient, Water-Tolerant, and Reusable Catalyst for the Synthesis of N-Methylamides

ZrOCl2·8H2O is a highly effective, water-tolerant, and reusable catalyst for the direct condensation of carboxylic acids and N,N¢-dimethylurea under microwave irradiation to give the corre- sponding N-methylamides in moderate to excellent yields. Notably, ZrOCl2·8H2O is a potentially useful green catalyst due to its low toxicity, easy availability, low cost, ease of handling, easy recovery, good activity, and reusability.

Open vessel mode microwave-assisted synthesis of 2-oxazolines from carboxylic acids

Microwave-assisted synthesis of 2-oxazolines from carboxylic acids using the open vessel technique is described. This efficient method involves direct condensation of carboxylic acids with excess 2-amino-2-methyl-1-propanol at 170 °C to give the corresponding 2-oxazolines in moderate to excellent yields.

Preparation, characterization and catalytic activity of polystyrene with pendent perfluoroalkylsulfonylimide groups

The new type of polystyrene with pendent perfluoroalkylsulfonylimide groups polymer (PPFSI or P-SO 2NHSO 2R f, where P is the polymer chain, R = CF 3, CF 2CF 2CF 2CF 3) was prepared by chemical modification of chlorosulfanated poly(styrene-co-divinybenzene) resins with perfluoroalkylsulfonylamides R fSO 2NH 2. Acid strength of the PPFSI was tested by the Hammett indicator method, acid contents of the PPFSI were determined by acid–base titration and the nature of chemical modification for the PPFSI was evaluated by IR, TGA and SEM. The results indicated that the PPFSI was a strongly acidic polymer, which could be tolerant of high temperature, and an effective catalyst for direct condensation of carboxylic acids and alcohols.

Arylboronic Acid Catalyzed Direct Condensation of Carboxylic Acids with Ureas.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Efficient Synthesis of Benzothiazoles by Direct Condensation of Carboxylic Acids with 2‐Aminothiophenol under Microwave Irradiation.

Carboxylic acids are converted to benzothiazoles by direct condensation with 2-aminothiophenol under microwave irradiation in the absence of solvent.

Solvent‐Free Microwave‐Assisted Efficient Synthesis of 4,4‐Disubstituted 2‐Oxazolines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Arylboronic Acid-Catalyzed Direct Condensation of Carboxylic Acids with Ureas

The first example of the catalytic direct condensation of carboxylic acids with ureas to give N-acylureas, N,N'-diacyl-2-imidazolidones, and poly(N,N'-diacyl-2-imidazolidone)s is described. Arylboronic acids bearing electron-withdrawing substituents are highly effective as catalysts for this condensation. Furthermore, a new and efficient one-pot procedure for the conversion of carboxylic acids and urea to nitriles via N-acylurea intermediates was accomplished by using arylboronic acid and rhenium(VII) oxo complexes as hybrid catalysts.

An Efficient Synthesis of Benzothiazoles by Direct Condensation of Carboxylic Acids with 2-Aminothiophenol under Microwave Irradiation

Carboxylic acids are converted to benzothiazoles by direct condensation with 2-aminothiophenol under microwave irradiation in the absence of solvent.

Solvent‐Free Microwave‐Assisted Efficient Synthesis of 4,4‐Disubstituted 2‐Oxazolines

Abstract4,4‐Disubstituted 2‐oxazolines have been synthesized by a microwave‐promoted solvent‐free direct condensation of carboxylic acids and disubstituted β‐amino alcohols in good to excellent yields. Zinc oxide is a very good solid support in cases where a Lewis acid is required. The method described herein is a very good, safe, clean, economical, and environmentally friendly alternative to the classical procedures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Direct condensation of carboxylic acids with polyethylene glycols catalyzed by Sc(OTf) 3

Esterification of soluble polymers by direct condensation of equimolar amounts of carboxylic acids with polyethylene glycols is achieved using catalytic Sc(OTf) 3 in toluene for the first time.

Direct Condensation of Carboxylic Acids with Alcohols: The Atom Economic Protocol Catalysed by Fe3+-Montmorillonite

Fe3+-montmorillonite clay catalyst was used for the first time to esterify various aliphatic, aromatic, α,β-unsaturated mono- and di-carboxylic acids and long chain fatty acids with alcohols under mild reaction conditions in good to excellent yields. The present heterogeneous catalytic system is a potential candidate not only for laboratory practice but also for commercial application and offers an environmentally safer alternative to the existing processes.

ChemInform Abstract: Formation of Carboxamides by Direct Condensation of Carboxylic Acids and Amines in Alcohols Using a New Alcohol‐ and Water‐Soluble Condensing Agent: DMT‐MM.

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Formation of carboxamides by direct condensation of carboxylic acids and amines in alcohols using a new alcohol- and water-soluble condensing agent: DMT-MM

Selective formation of carboxamides in an alcohol or water by an exceptionally convenient one-step procedure in which a condensing agent is simply added to a mixture of acids and amines has been achieved successfully by using a new condensing agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). Activation of carboxylic acids by DMT-MM in the presence of amines and subsequent aminolysis of the resulting acyloxytriazine in alcoholic solvents occurred selectively and led to the formation of carboxamides in excellent yields. The rate of aminolysis of the acyloxytriazine intermediate can be estimated to be about 2×10 4 times greater than that of methanolysis. The amide/ester selectivity observed using DMT-MM was much larger than that obtained with DCC or EDC. Condensation of polar substrates, such as amino acid esters and their hydrochlorides, glucosamine hydrochloride, sodium acetate and dicarboxylic acids, proceeded successfully in MeOH, water or aqueous MeOH in good yields. The present reaction is technically quite simple and easy to achieve. It proceeds by simple mixing of acids, amines and DMT-MM without any additives, and the MeOH is readily removable by a rotary evaporator after completion of the reaction.