Acetyl fluoride Acid chlorides, preparation

Before describing the preparation and properties of trifluoroacetate compounds in general, particular consideration will be given to the parent acid. The normal commercial preparation of trifluoroacetic acid is the electrolytic fluorination of acetyl fluoride or chloride 210). Other preparative methods include the oxidation of trifluorotoluidine or other trifluoromethyl aryl derivatives 247) and the hydrolysis of trifluoro-acetylchloride (6). 

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. ... 

Acylation (see also Acetylation, Cathylation) Acyl fluorides. Benzoylchloride (see Hippuric acid, preparation). N-Carbonylsulfamic acid chloride. Chloroacetic anhydride. Chloroacetyl chloride. Magnesium. Mesyl chloride. Methanesulfonic anhydride. 1-Morpholinocyclo-hexene. Pyridine. Sodium diisopropylamide. Sodium hydride. Trifluoroacetic anhydride. 

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-... 

Monoprotected P-keto-aldehydes may be prepared by the a-dialkoxymethyl-ation of pre-formed enolates or enamines with trimethyl orthoformate and boron trifluoride diethyl etherate. Regiospecificity is maintained when the enolate is released from the silyl enol ether with methyl-lithium. P-Keto-acetals or P-diketones may also be formed by acylation of enol ethers with acid chlorides. High yields depended on the use of activated acid chlorides, such as a-halo- or a-cyano-acetyl chlorides. Enaminosilanes are acylated by a wide range of acid chlorides in the presence of potassium fluoride and a crown ether, giving very high yields of the enaminone [equation (46)]. Under the reaction conditions,... 

Acetic formic anhydride has been prepared by the reaction of formic acid with acetic anhydride2 3 and ketene,4,5 and of acetyl chloride with sodium formate.6 The present procedure is essentially that of Muramatsu.6 It is simpler than others previously described and gives better yields. It is easily adapted to the preparation of large quantities, usually with an increase in yield. Acetic formic anhydride is a useful intermediate for the formyl-ation of amines,3,7 amino acids,8,9 and alcohols,2,10 for the synthesis of aldehydes from Grignard reagents,11 and for the preparation of formyl fluoride.12... 

In addition to the methods of preparation given in connection with the procedure for the acetylation of thiophene with acetyl chloride in the presence of stannic chloride, 2-acetothienone has been prepared from thiophene and either acetyl chloride or acetic anhydride in the presence of iodine, hydriodic acid, silica-metal oxides, zinc chloride, or inorganic oxyacids. It has also been prepared from thiophene and acetic acid in the presence of hydrogen fluoride or phosphorus pentoxide. The acylation in the presence of phosphorus pentoxide is particularly useful with higher aliphatic acids. ... 

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