Anhydrides synthesis from acyl halides

Interchange of halogen is a means of synthesis of certain acyl halides which cannot be conveniently prepared by other methods. Acetyl fluoride is made from acetyl chloride and sodium hydrogen fluoride in acetic anhydride solution." By passing a stream of hydrogen bromide through oxalyl chloride an 85% yield of oxalyl bromide, (COBr), is obtained. The bromide cannot be made by the action of phosphorus pentabromide on oxalic acid. The method has also been applied to the preparation of acetyl bromide and iodide and other acyl iodides. ... 

Anhydrides—Continued reduction to alcohols, 155 reduction to lactones, 535 Arenes, see Hydrocarbons, aromatic Amdt-Eistert reaction, 433, 487, 573 Aryl esters. Fries rearrangement, 344 hydrolysis, 169 preparation, 169 Aryl halides, see Halides Atyloxy acids, preparation, by aceto-acetic ester synthesis, 430 by malonic ester synthesis, 429 from atyloxy alcohols, 419 from atyloxy cyanides, 414 preparations listed in table 48, 460 Aryloxy acyl halides, preparation, 547 preparations listed in table 61, 553 Aryloxy esters, preparations listed in table 55, 516... 

Pyridine is used in catalytic amounts and acylpyridinium salts are assumed to be the reactive acylating agents. The method can be applied to the synthesis of both symmetrical and unsymmetrical acid anhydrides. " These can also be obtained in many cases directly from the acid halide and the sodium carbox-ylate without using a solvent or a catalyst. Tiiis approach has been described for a number of mixed acid anhydrides. Thus acetic palmitic anhydride (70%), butyric myristic anhydride (81%) and caproic lauric anhydride (85%) were prepared by heating the components for 2 h at 90 °C. 75 These anhydrides were successfully employed for the N-acylation of amino sugars. 7 ... 

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