Pd-catalysed decarboxylative Suzuki reactions and orthogonal Cu-based O-arylation of aromatic carboxylic acids

Pd-catalysed decarboxylative Suzuki reactions and orthogonal Cu-based O-arylation reactions of aromatic carboxylic acids are reported. The new reactions may provide alternative routes for the synthesis of some biaryls and aromatic carboxylic esters.     

S-benzylthiouronium salts of some carboxylic acids,sulfonic acids,and phenols

116 S-Benzylthiouronium suits have been prepared and were, if possible, checked by titration with perchloric acid in glacial acetic acid on a semi-micro scale. Out of these, 110 are salts of carboxylic acids, 2 of snlfonic acids, and 4 of nitrophenols. The melting points determined according to a standard procedure are given.     

Ligand-free copper-catalyzed O-arylation of nitroarenes with phenols

The first example of ligand-free copper-catalyzed O-arylation of nitroarenes with phenols was developed, achieving unsymmetrical diaryl ethers in moderate to excellent yields. This arylation proceeded smoothly without promotion of the ligands, and displayed great functional group compatibility. Thus, the method represents a new, facile, and cost-effective approach to access unsymmetrical diaryl ethers.     

Facile amide bond formation from carboxylic acids and isocyanates

A wide variety of carboxylic acids in the form of their salts condense with aryl isocyanates at room temperature with loss of carbon dioxide to give the corresponding amides in high yield. Application of the reaction to acyl isocyanates gives unsymmetric imides. The reaction is compatible with hydroxyl groups and both Fmoc and Boc protecting groups for amines and is applicable to aliphatic, aromatic, and heteroaromatic acids.     

Facile reaction of carboxylic acids with isonitriles in toluene

Isonitriles react with low concentrations of carboxylic acids in toluene at 110 °C to give N-formylamides in yields generally above 70%. These concentrations can be obtained either by syringe pump addition of a toluene solution of the acid, or by using a suspension of the acid if it has limited solubility in toluene at room temperature.     

Facile electrochemical transformation of diazonium salts into carboxylic acids

The electrolyses of aryldiazonium tetrafluoroborates in dry DMF and Bu₄NHSO₄ as solvent-supporting electrolyte system, in the presence of CO₂ led to the corresponding arylcarboxylic acids in very good yields.     

Intramolecular O-arylation of phenols with phenylboronic acids: application to the synthesis of macrocyclic metalloproteinase inhibitors

[reaction: see text]. The copper acetate mediated intramolecular O-arylation of phenols with phenylboronic acid pseudopeptides is the key step in the preparation of macrocyclic biphenyl ether hydroxamic acid inhibitors of collagenase 1 and gelatinases A and B. The intramolecular macrocyclization was found to be mild and tolerant of common chemical functionality. This methodology should provide a general route to macrocyclic biphenyl ethers.     

Chemoselectivity in the Cu-catalyzed O-arylation of phenols and aliphatic alcohols

An orthogonal set of Cu-catalysts for the selective mono-arylation of alkyl aryl diols using aryl iodides is presented. Picolinic acid ligated copper catalyst provided phenol O-arylation only, while alkyl aryl ethers are generated by ligand-free copper catalyst in the presence of 2 equivalents NaOt-Bu.     

Quantitative studies on the pyrolytic methylation of simple carboxylic acids and phenols

Efforts have been made to establish the experimental parameters which affect the pyrolytic methylation of simple carboxylic acids and phenols, and to evaluate the importance of these parameters on a sound quantitative basis.     

Rules governing vapor-phase extraction of carboxylic acids and phenols from aqueous solutions

The influence of the molecular structure of the components to be extracted and the type of the extractant used on the effectiveness of vapor-phase extraction from water was studied for the example of low-molecular-weight carboxylic acids C₂-C₆ and phenols. Extraction parameters were found to depend on the length of the analyte molecule and its polarity. The experimental data and correlations observed substantiated the validity of the suggested mechanism of vapor-phase extraction. Changes in the Gibbs energy of extraction equilibrium as the length of the analyte molecule (in the homologous series of organic acids C₂-C₆) and molecule polarity (for the example of cresol isomers) increased were evaluated.     

Secondary deuterium isotope effects on the acidity of carboxylic acids and phenols

Secondary deuterium isotope effects (IEs) on acidities have been accurately measured by an NMR titration method applicable to a mixture of isotopologues. Deuteration definitely decreases the acidity of carboxylic acids and phenols, by up to 0.031 in the DeltapK per D. For aliphatic acids, the IEs decrease as the site of deuteration becomes more distant from the OH, as expected, but a surprising result is that IEs in both phenol and benzoic acid do not decrease as the site of deuteration moves from ortho to meta to para. The experimental data are supported by ab initio computations, which, however, substantially overestimate the IEs. The discrepancy does not seem to be due to solvation. The IEs originate in isotope-sensitive vibrations whose frequencies and zero-point energies are lowered upon deprotonation. In the simplest case, formate, the key vibration can be recognized as the C-H stretch, which is weakened by delocalization of the oxygen lone pairs. For the aromatic acids, delocalization cannot account for the near constancy of IEs from ortho, meta, and para deuteriums, but the observed IEs are consistent with calculated vibrational frequencies and electron densities. Moreover, the ability of the frequency analysis to account for the IEs is evidence against an inductive origin.     

Microdetermination of phenols, carboxylic acids and phenolic acids by potentiometric and visual titrations in dimethylformamide

Potentiometric titration of phenols with sodium methoxide in dimethylformamide, with a glass-calomel electrode system, is limited to monohydric phenols substituted with electron-attracting groups and dihydric phenols in which the two -OH groups are substituted in isolated benzene rings. Brilliant Orange has proved to be a suitable indicator in the titration of all types of mono- and dihydric phenols. Titan Yellow is recommended as indicator for the titration of carboxylic acids. Simultaneous visual titration of -OH and -COOH groups is also described. A detailed study with 62 structurally different compounds covering the various groups is reported, and a suitable procedure for the microdetermination of each class of these compounds with an error of +/- 0.2% absolute or less is presented.     

Facile N-arylation of amines and sulfonamides and o-arylation of phenols and arenecarboxylic acids

An efficient, transition-metal-free procedure for the N-arylation of amines, sulfonamides, and carbamates and O-arylation of phenols and carboxylic acids has been achieved by allowing these substrates to react with a variety of o-silylaryl triflates in the presence of CsF. Good to excellent yields of arylated products are obtained under very mild reaction conditions. This chemistry readily tolerates a variety of functional groups.     

Extraction of aromatic carboxylic acids and phenols by strongly solvating organophosphorus compounds and sulfoxides

Summary This paper contains a systematic comparison of the extracting power and selectivity of tri-n-butylphosphate (TBP), di-n-octylsulfoxide (DOSO) and tri-n-octylphosphinoxide (TOPO) in the extraction of aromatic carboxylic acids and phenols from aqueous perchloric acid solutions of varying pH. Organophosphorus compounds and sulfoxides form hydrogen bonds to proton-donating molecules. This rather specific interaction can be used for solvent extraction of acidic compounds or for Chromatographic separations. A simple model describes the influence of the main experimental parameters on the liquid-liquid distribution behaviour.The most interesting Chromatographic phase systems for the separation of acidic compounds by column liquid chromatography are liquid-liquid systems which contain a strongly solvating reagent in the liquid stationary phase and liquid-solid systems with strongly solvating compounds adsorbed on the hydrophobic adsorbent surface.

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Extraktion aromatischer Carbonsäuren und Phenole mit stark solvatisierenden Organophosphorverbindungen und Sulfoxiden

Zusammenfassung Das Extraktionsvermögen und die Selektivität von Tri-n-butylphosphat (TBP), Di-n-oktylsulfoxid (DOSO) und Tri-n-oktylphosphinoxid (TOPO) gegenüber aromatischen Carboxylsäuren und Phenolen aus wäßrigen perchlorsauren Lösungen mit verschiedenen pH-Werten wurde systematisch verglichen. Organophosphorverbindungen und Sulfoxide bilden zu Molekülen, die Protonendonatoren sind, Wasserstoffbrückenbindungen aus. Diese ziemlich spezifische Wechselwirkung kann zur Lösungsmittelextraktion saurer Verbindungen oder bei chromatographischen Trennungen eingesetzt werden. Der Einfluß der wichtigsten Versuchsparameter auf das Flüssig-flüssig-Verteilungsverhalten läßt sich durch ein einfaches Modell beschreiben.-Die zur Trennung saurer Verbindungen durch Säulen-Flüssigkeits-Chromatographie interessantesten Phasensysteme sind Flüssig-flüssig-Phasensysteme, in denen die stationäre Flüssigkeit eine stark solvatisierende Verbindung enthält, sowie Flüssig-fest-Systeme, in denen stark solvatisierende Verbindungen an der Oberfläche eines hydrophoben Adsorbens adsorbiert sind.

     

Gold(I)-catalyzed intermolecular addition of phenols and carboxylic acids to olefins

Ph3PAuOTf can catalyze efficient intermolecular addition of phenols and carboxylic acids to olefins under relatively mild conditions.     

Copper-mediated O-arylation of lactols with aryl boronic acids

A novel and efficient method to access phenolic glycosides has been established by using copper-mediated coupling reaction of aryl boronic acids with hemiacetals. The reaction enjoyed a wide range of substrate scope, and many phenolic glycosides can be synthesized in good yields.     

Reaction of benzoxazine-based phenolic resins with strong and weak carboxylic acids and phenols as catalysts

The reaction of 3,4-dihydro-3,6-dimethyl-2H-1,3-benzoxazine using strong and weak carboxylic acids and phenols as catalysts has been studied using Fourier transform infrared (FTIR) spectroscopy. The auto-accelerated curing using sebacic acid as catalyst is further documented using ¹H-nuclear magnetic resonance (NMR) and dielectric analysis. Termination of curing, using strong acids or no catalyst, are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1913–1921, 1999     

Cu-nanoparticle catalyzed O-arylation of phenols with aryl halides via Ullmann coupling

Recyclable Cu-nanoparticles provide an efficient, economic, and novel method for the synthesis of diaryl ethers via Ullmann type coupling. This method provides a wide range of substrate applicability and avoids the use of a heavy metal co-catalyst and gives diaryl ethers in satisfactory yields.     

Photolabile protection of alcohols, phenols, and carboxylic acids with 3-hydroxy-2-naphthalenemethanol

Irradiation of alcohols, phenols, and carboxylic acids "caged" with the (3-hydroxy-2-naphthalenyl)methyl group results in fast (k(release) approximately = 10(5) s(-1)) release of the substrates with good quantum (Phi = 0.17-0.26) and chemical (>90%) yields. The initial byproduct of the photoreaction, 2-naphthoquinone-3-methide, reacts rapidly with water (k(H2O) = 144 +/- 11 s(-1)) to produce parent 3-hydroxy-2-naphthalenemethanol. The o-quinone methide intermediate can be also trapped by other nucleophiles or converted into a photostable Diels-Alder adduct with ethyl vinyl ether.     

Reaction of trichlorides of phosphono carboxylic acids with acetylacetone,acetoacetic ester,and phenols

Reactions of trichloride of phosphono carboxylic acid with β-dicarbonyl compounds proceed at the active methylene group with the formation of the С-acylation product with a small admixture of the product of O-acylation. The C-acylation products undergo intramolecular condensation to form 1,2-oxophosphorines and compounds of the phosphate structure. The condensation of trichlorides with phenols proceeds selectively at the carbonyl carbon atom leading to C-phenyl esters. With more acidic phenols the splitting of the Р–С bond in the substitution product occurs.