Acid anhydrides from silver salts

Alkyl esters of trifluoromethanesulfonic acid, commonly called triflates, have been prepared from the silver salt and an alkyl iodide, or by reaction of the anhydride with an alcohol (18,20,21). Triflates of the 1,1-dihydroperfluoroalkanols, CF2S020CH2R can be prepared by the reaction of perfluoromethanesulfonyl fluoride with the dihydroalcohol in the presence of triethylamine (22,23). Triflates are important intermediates in synthetic chemistry. They are among the best leaving groups known, so they are commonly employed in anionic displacement reactions. 

Diorgano tellurium dicarboxylates were prepared from dialkyl and diaryl tellurium derivatives. Aliphatic carboxylic acids, aromatic carboxylic acids, their sodium or silver salts, and carboxylic acid anhydrides were used as reagents. Dicarboxylic acids such as succinic acid and phthalic acid were reported to give monomeric carboxylates when... 

Attempts to use a Lewis acid to anomerize the ester linkage at C-l from /3 to a have thus far been mostly unsuccessful however, application of Bonner s249 procedure, involving anomerization of acetylated aldoses in an acid anhydride containing an acid catalyst, was found246 to be applicable to the acetylated D-glucopyranuronate series also. Thus, /3 —> a anomerization of methyl tri-0-acetyl-l-0-propanoyl-/3-D-glucopyranuronate (prepared by the silver salt method) was achieved... 

Although this is the classical method of anhydride formation it has been replaced to a large extent by the acylation of free carboxylic acids (method 341). The conditions employed and the solvents used in this reaction vary widely. Excellent directions are given for the preparations of nicotinic anhydride (89%) and acetic propionic anhydride (60%) from the respective potassium and sodium salts of the carboxylic acids. Silver salts of acids have also been used. The reaction has been extended to the preparation of mixed anhydrides of short- and long-chain fatty acidsbut has failed in the preparation of mixed anhydrides of substituted benzoic acids. ... 

The acid reduces ammoniacal. silver nitrate solution, and with sodium nitrite gives a yellow diazo-compound, which couples with resorcinol to give a bluish-red dye. Wren dissolved in sodium hydroxide and treated with acetic anhydride, the amino-acid yields an acetyl derivative, which separates in colourless prisms from water, and yields amorphous calcium and magnesium salts. ... 

Several other metal salts have been proposed to react with acid halides to give acid anhydrides in good yield. Thus, thallium carboxylates in etheral suspension may be treated with acid halides to lead to acid anhydrides in high yield. The method has the advantage that thallium chloride can be separated by filtration and the product is isolated after evaporation of the solvent. Another synthetic possibility exists in the desulfurization of thioesters with mercury(II) carboxylates. Mercuiy(II) carboxylates can also be reacted with triethyl phosphite or tri-n-butylphosphine to provide acid anhydrides in yields of 60-80%. Another possibility is offered by the reaction of 1 mol of iV,Af-dicyclohexylthiourea and 2 mol of silver or mercury(II) carboxylates. Mixed carboxylatocarbamato anhydrides follow from the room temperature reaction of iV, -dialkylcarbamato metal derivatives with acid chlorides. Either Na, Cu", Ti" or V" are employed. ... 

A considerable amount of research has been concerned with the nature of the electrophiles that are involved in Friedel-Crafts acylation reactions. We will summarize the main points. Acyl halides and carboxylic acid anhydrides have been known, for many years, to form stable complexes with a variety of acid catalysts. A well-defined product is formed between acetyl fluoride and boron trifluoride at low temperatures. Analytical and conductivity data characterized the material as acetylium tetrafluoroborate, and this was further confirmed by IR measurements. In the system acetyl chloride-aluminum chloride the acetylium ion can be differentiated from the donor-acceptor complex involving the carbonyl group by means of their IR carbonyl stetching frequencies. A number of other acyl fluorides have been shown to form well-defined acylium salts by interaction with a number of metal fluorides. Acylium salts can also be prepared from acyl chlorides by means of metathetical reactions involving anhydrous salts such as silver hexafluoroantimonate. As well as characterization by means of IR spectroscopy, acylium salts have been studied in non-nucleophilic solvents by NMR spectroscopy. The NMR data for the ben-... 

If triphenylmethyl chloride in ether is treated with sodium, a yellow colour is produced due to the presence of the anionic spiecies PhsC". Alternatively, if triphenylmethyl chloride is treated with silver perchlorate in a solvent such as THF, the triphenylmethyl cation is obtained. More conveniently, triphenylmethyl salts, PhsC X", can be obtained as orange-red crystalline solids from the action of the appropriate strong acid on triphenylcarbinol in ethanoic or propanoic anhydride solution. The perchlorate, fluoroborate and hexafluoro-phosphate salts are most commonly used for hydride ion abstraction from organic compounds (e.g. cycloheptatriene gives tropylium salts). The salts are rather easily hydrolysed to triphenylcarbinol. 

Copper acetate, ferrous acetate, silver acetate [563-63-3] basic aluminum acetate, nickel acetate [373-02-4] cobalt acetate, and other acetate salts have been reported to furnish anhydride when heated. In principle, these acetates could be obtained from low concentration acetic acid. CompHcations of soHds processing and the scarcity of knowledge about these thermolyses make industrial development of this process expensive. In the eady 1930s, Soviet investigators discovered the reaction of dinitrogen tetroxide [10544-72-6] and sodium acetate [127-09-3] to form anhydride ... 

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