羧酸直接酰胺化的一个新方法

N, N-二甲基取代酰胺可以方便地由脂肪族或芳香羧酸与四(二甲氨基)硅烷在无水溶剂中反应制得。     

Development of a one-pot method for the homologation of aldehydes to carboxylic acids

A highly efficient method is described for the one-carbon homologation of aldehydes to carboxylic acid derivatives employing the reaction of a 1,1-bis-dimethylphosphonate derivative with the aldehyde and controlled acid hydrolysis of the derived α-phosphonoenamine intermediate.     

The one-pot conversion of carboxylic acids to aldehydes via activated silyl carboxylates.

The trasformation of acids into aldehydes in a one-pot process is performed through the thermal decomposition of pentacoordinated silicon species.     

Efficient and one-pot synthesis of novel sulfamates from carboxylic acids

Effective synthesis of novel sulfamates from various carboxylic acids has been developed in the presence of chlorosulfonyl isocyanate (CSI) in mild conditions. Several acids, bases and solvents effects were investigated for one-pot synthesis sulfamates as a catalyst. Finally, triflic acid was found to possess efficiently under optimized conditions in acetonitrile. This method is easy, fair price and practical. It can be synthesized on grams and milligrams scale.     

A convenient method for the conversion of hindered carboxylic acids to N-methoxy-N-methyl (Weinreb) amides

The conversion of sterically hindered carboxylic acids to N-methoxy-N-methyl amides can be efficiently carried out with 1.1 equiv of methanesulfonyl chloride, 3 equiv of triethylamine, and 1.1 equiv of N-methoxy-N-methylamine. Yields for this process range from 59% to 88%. The major byproduct in these reactions, N-methoxy-N-methylmethanesulfonamide, can be removed by placing the product mixture under vacuum for 14-24 h.     

A novel stereoselective one-pot conversion of alcohols into alkyl halides mediated by N,N'-diisopropylcarbodiimide

Alcohols can be converted in high yields to the corresponding alkyl halides in a one-pot procedure via the corresponding O-alkylisourea; very short reaction times are possible when microwave irradiation is used.     

A novel one-pot conversion of aldehydes to trifluoromethylated bromoallylic alcohols

[reaction: see text]. One-pot conversion of aldehydes to trifluoromethylated bromoallylic alcohols in the presence of titanium isopropoxide and triphenylphosphine is described.     

A simple method for the conversion of carboxylic acids into thioacids with Lawesson’s reagent

A one-step protocol for the conversion of carboxylic acids to thioesters, using Lawesson’s Reagent, has been developed.     

A colorimetric method for the determination of carboxylic acids

A new colorimetric method for the determination of carboxylic acids using bromocresol green reagent is established. The formed color follows Beer's Lambert law and is stable for 24 hr. The method is successfully applied for measuring the disappearance of volatile fatty acids in P. oxalicum culture media. The method is reproducable and is used also for the quantitative determination of carboxylic acids in Dowex 1-X8 eluates. A linear relationship between the pK₁ of different carboxylic acids and the calculated molar extinction coefficients of the color formed at 440 nm is demonstrated.     

Divergent pathway for the solid-phase conversion of aromatic acetylenes to carboxylic acids, alpha-ketocarboxylic acids, and methyl ketones

An efficient divergent pathway for the selective and quantitative solid-phase conversion of aromatic acetylenes to the corresponding carboxylic acids, alpha-keto-carboxylic acids, and methyl ketones is presented. A range of aromatic trimethylsilyl-protected acetylene building blocks was synthesized in excellent yields using a Sonogashira cross-coupling protocol and used in solid-phase synthesis on PEGA resin. Dependent on the selection of conditions, the same solid-supported alkyne could be quantitatively converted to an aromatic carboxylic acid, an aromatic alpha-ketocarboxylic acid, or an aromatic methyl ketone. The conversion to carboxylic acid involved an OsO4/NaIO4/HMTA-mediated oxidative cleavage of the silyl-deprotected alkyne to provide the aromatic carboxylate in excellent yield. The alpha-ketocarboxylic acids were obtained by direct treatment of the trimethylsilyl-protected alkyne with OsO4/NMO/HMTA, while the ketones were obtained by simple acid-mediated hydration of the alkyne using aqueous TFA. In general, all products were obtained in excellent purities, typically above 90%. In addition, it was shown that the alkyne-containing building blocks could easily be incorporated into resin-bound peptides and after chemoselective conversion of the alkyne the new functional groups could be used for further derivatization into peptidomimetic compounds.     

Mild conversion of beta-diketones and beta-ketoesters to carboxylic acids

A mild protocol for the conversion of beta-ketoesters and beta-diketones to carboxylic acids with use of CAN in CH3CN is described. The method is compatible with a number of functional groups, and can generate carboxylic acids under neutral conditions at room temperature. The reaction is fast and general, providing an alternative method to the commonly used malonic ester acid preparation. Initial mechanistic studies show that initial oxidation of the enol form of the beta-dicarbonyl initiates the reaction. The presence of nitrate as an oxidant ligand or as an additive is critical for success of the reaction.     

Mild one-pot conversion of carboxylic acids to amides or esters with Ph3P/trichloroisocyanuric acid

The reaction of trichloroisocyanuric acid (TCICA) and triphenylphosphine in the presence of a carboxylic acid results in the in situ formation of the corresponding acid chloride under mild conditions. Subsequent addition of amines or alcohols, in the presence of a tertiary amine affords the corresponding amides, or esters, in good to excellent yields. The methodology was applied to the synthesis of a dipeptide.     

A novel system for the synthesis of nitriles from carboxylic acids

A simple, mild and high yielding method for the conversion of various carboxylic acids to nitriles has been developed using diphosphorus tetraiodide in combination with ammonium carbonate at room temperature.     

A convenient method for the conversion of N-acyloxazolidinones to hydroxamic acids

Treatment of N-acyloxazolidinones with hydroxylamines using samarium triflate as a Lewis acid provides the corresponding hydroxamic acids in 50-98% yields at room temperature. The conversion proceeds with high degree of chemoselectivity and without racemization of chiral centers alpha- to the acyl group. [reaction: see text]     

General and practical conversion of aldehydes to homologated carboxylic acids

The reaction of aldehydes with trichloromethide followed by sodium borohydride or sodium phenylseleno(triethyl)borate under basic conditions affords homologated carboxylic acids in high yields. This operationally simple procedure provides a practical, efficient alternative to other homologation protocols. The approach is compatible with sensitive aldehydes including enals and enolizable aldehydes. It also offers convenient access to alpha-monodeuterated carboxylic acids.     

A novel and efficient one-pot method to Biginelli-like scaffolds

A novel and efficient one-pot method for the preparation of fused ring 3,4-dihydropyrimidin-2(1H)-ones and thiones from cyclocondensation of aldehydes, cyclic ketones and urea or thiourea using a catalytic amount of cupric chloride under mild conditions reaction is described. This new method has the advantage to give high yields, to be completed in short reaction times and simple product isolation procedure.