Acetyl fluoride, reaction

The described procedure, first applied by Colson and Freden-hagen, is useful for the preparation of a wide variety of acyl fluorides. The yields are normally 80-90%. Some examples of acyl fluorides prepared are listed in Table I. Benzoyl fluoride can also be employed as a convenient source of acetyl fluoride by reaction with acetic acid. ... 

In this procedure, the ketone is first converted to its enol acetate by reaction with acetic anhydride in the presence of a proton acid. Since this enol acetylation is performed under equilibrating conditions, the more stable enol acetate (usually the more highly substituted isomer) is produced. Acetylation of this enol acetate, catalyzed by the Lewis acid boron trifluoride, usually leads to the formation of the enol acetate of a /3-diketone which is cleaved by boron trifluoride to form acetyl fluoride and the borofluoride complex of the /3-diketone. Thus, this procedure offers a convenient and general synthetic route... 

The liquid state of arsenic(III) fluoride and miscibility with many solvents and other liquids is an advantage permitting variation of the reaction conditions over a wide range. The first reported application of arsenic(III) fluoride as a fluorinating agent was the conversion of acetyl chloride into acetyl fluoride.3... 

Reaction of 2,2-difluoro-2-(methoxycarbonyl)acetyl chloride (3) with potassium fluoride affords 2,2-difluoro-2-(methoxycarbonyl)acetyl fluoride (4) in 90 % yield, which is one of the precursors for the preparation of perfluorovinyl ethers containing a carboxylic group.30... 

Another interesting substitution reaction is the conversion of l-methoxybicyclo[2.2.2]octane (3a) and l-methoxy-4-methylbicyclo[2.2.2]octane (3b) with acetyl fluoride and boron trifluoride,9 but this has not yet been extended to other substrates. 

Acetyl fluoride (A) reacts with water (B) to form acetic acid (C) and hydrofluoric acid (D). The reaction is carried out in acetone (an inert solvent) so that the concentrations can be kept low and the reaction under control. The equation is... 

The transient nature of carbocations arises from their extreme reactivity with nucleophiles. The use of low-nucleophilicity counterions, particularly tetrafluorobo-rates (B I, ), enabled Meerwein in the 1940s to prepare a series of oxonium and carboxonium ion salts, such as R30+BF4 and HC(OR)2+BF4, respectively.13 These Meerwein salts are effective alkylating agents, and they transfer alkyl cations in SN2-type reactions. However, simple alkyl cation salts (R 1 BF4 ) were not obtained in Meerwein s studies. The first acetyl tetrafluoroborate—that is, acetylium tetrafluor-oborate—was obtained by Seel14 in 1943 by reacting acetyl fluoride with boron trifluoride at low temperature [Eq. (3.1)]. 

A very reactive halogen atom, such as that of mi acyl or sulfonyl halide, is replaced by fluorine by the action of almost any inorganic fluoride. The most convenient method consists in heating gently a mixture of an acyl or sulfonyl chloride with zinc or antimony fluoride in an apparatus which permits the acyl fluoride to distil as it is formed. The acyl fluoride usually boils about 40° lower than the chloride, and its removal from the reaction mixture results in quantitative yields. Com- plete interchange also can be effected with hydrogen fluoride, but more elaborate equipment is required. Good results have been reported for the synthesis of formyl and acetyl fluorides from mixtures of fonnic or... 

Acetyl Fluoride, (a)2 In a pressure bottle stoppered with rubber is placed 150 g. of acetyl chloride It is cooled to —15°, and 10 g. of anhydrous zinc fluoride is introduced the bottle is stoppered and allowed to warm to room temperature with shaking.. It is then cooled, a second 10-g. portion of the salt is added, and the bottle is stoppered and shaken as before. When 100 g. of zinc fluoride has been added in this way the temperature is allowed to rise gradually to 50°. The reaction mixture is cooled, and the product is distilled. Acetyl fluoride boils at 20° the yield is quantitative. 

In contrast to other known fluorinated /3-sultones, reaction of compound 48 with triethylamine does not give the expected isomer 49, but only its decomposition products pentafluoropropionyl fluoride 50 and fhiorosulfonyldifluoro-acetyl fluoride 51 (Scheme 10) <2003JFC(121)147>. 

The reaction of trimethyl(perfluorophenyl)silanc with carbonyl centers occurs under mild reaction conditions, similar to those used for trimethyl(trifluoromethyl)silane. Acetyl fluoride in acetonitrile in the presence of catalytic amounts of potassium fluoride gives l-fluoro-l-(penta-fluoropheny )ethyl acetate (12) in 65% yield. When the bifunctional acid fluoride perfluoro-glutaryl difluoride reacts with trimethyl(perfluorophcnyl)silane in acetonitrile in the presence of potassium fluoride, the perfluorinated diketone perfluoro(l,5-diphenylpcntane-l,5-dione)... 

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-... 

Sulfonyl fluorides are readily obtained from sulfonyl chlorides and KF or KHF2j even in an aqueous medium.801"804 Carboxylic acid fluorides are formed when the acid chlorides are heated with dry KF and can be removed continuously from the reaction mixture by distillation through a column formyl and acetyl fluorides are thus obtained when the acid is heated with benzoyl chloride and KF.805,806 Xylene or acetamide may be used as diluent. Further, a>chloro and at-bromo fatty esters, nitriles, and amides react with KF at temperatures around 100-150°. 

The reactions of perfluoroisobutene with sodium salts of malonic esters are difficult to control, owing to rearrangement and base catalysed cyclization, but when the complex BFs NEts is used as HF acceptor, condensation is readily controlled (see Scheme 15 and p. 99) and yields of up to 50% of allene (39) obtained. Antimony pentaliuoride catalyses the electrophilic addition of acid fluorides to 1,1-difluoro- and trifluoro-ethylene. Propiophenones, PhCO CHX-CFs (X = H or F), are obtained from benzoyl fluoride, but with acetyl fluoride, further condensation occurs, and trifluoroethylene yields the jS-diketone, CF3-CHF-CO-CH2Ac. ... 

Hexabenzyl-yS-D-ribofuranosyl-/3-D-ribofuranoside was obtained by reaction of 2,3,5-tri-O-benzyl-D-ribofuranose, or its 1-trimethylsilyl derivative, with the corresponding/9-glycosyl fluoride. Per-0-benzylated ot- and /S-gluco-, yS-galacto-, and -xylo-pyranosyl fluorides have been prepared from the corresponding per-O-acetylated fluorides in 17 - 34% yield by phase-transfer catalyzed benzyl-ation. 

Ether suspensions of these salts undergo 0-acetylation on treatment with acetyl chloride at —78°, and exclusive C-acylation with acetyl fluoride at ambient temperature. Assuming that acetyl fluoride is the harder acid, the above-mentioned reactions are in violation of the HSAB principle. 

Similar to perfluoroalkanesulfonic acids, the yield of the fluorination reaction decreases with the increasing chain length of the starting material. For example, the electrochemical fluorination of acetyl fluoride yields 76% of perfluoroacetyl fluoride, whereas the fluorination of octanoyl fluoride yields only 10% of perfluorooctanoyl fluoride. The yield is also lower when the readily available acid chlorides, and not the fluorides, are employed as starting materials. A major side reaction of the fluorination of acid chlorides such as octanoyl chloride is the formation of cyclic products. Other by-products and impurities present in PFCA fluorides obtained by electrochemical fluorination include short-chain PFCA fluorides, perfluoroalkanes, COFj, and HF. Perfluorooctanoyl fluoride, the most important PFCA, was industrially synthesized from the corresponding chloride despite the lower yield and formation of cyclic by-products. ... 

As in the case of Fluorouracil, newer syntheses of Floxuridine relied on direct fluorination of uracil derivatives. Fluorination of uridine 31 was done using fluorine [19], acetyl fluoride [20], and CF3OF [21], The latter reagent gave good but still moderate yield of the product 4 (47 %). The use of a two-step reaction sequence, Le. fluorination of diacetoxy derivative 32 and hydrolysis, improved the yield of 4 to 82 % over two steps [21, 22],... 

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