Fluonnated carboxylate

Alkylation of fluonnated carboxylate [4J] and sulfinate anions [42] occurs readily (equations 37 and 38)... 

The discussion of acylation reactions in this chapter is focused on fluonnated carboxylic acid derivatives and their use to build up new fluorine-containing molecules of a general preparative interest Fifteen years ago, fluonnated carboxylic acids and their derivatives were used mainly for technical applications [/] Since then, an ever growing interest for selectively fluonnated molecules for biological applications [2, 3, 4, 5] has challenged many chemists to use bulk chemicals such as tnfluoroacetic acid and chlorodifluoroacetic acid as starting materials for the solution of the inherent synthetic problems [d, 7,, 9]... 

Acylation of various oxygen functions by use of common and commercially available fluonnated carboxylic acid denvatives such as trifluoroacetic anhydride or the corresponding acyl halides have already been discussed sufficiently in the first edition [10] Therefore only exceptional observations will be described in this section In the past 15 years, many denvatizations of various nonfluonnated oxygen compounds by fluoroacylation were made for analytical purposes. Thus Mosher s acid chlorides for example became ready-to-use reagents for the determination of the enantiomeric purity of alcohols and amines by NMR or gas-liquid chromatographic (GLC) techniques [//] (equation 1)... 

The decarboxylation reactions of fluonnated carboxylic acids are similar to those of their nonfluonnated counterparts, but predictably many exceptions exist The oxidation of the potassium salts of perfluoro acids with potassium persulfate leads to decarboxylation and coupling [93] (equation 59)... 

Apart from these synthetically impractical examples of hydrolysis of chloro-fluorocarbons, there are useful applications converting some chlorofluorocarbons to fluonnated carboxylic acids. As an alternative to the use of the highly corrosive fuming sulfuric acid, normally used in batch processes, a continuous hydrolytic process for converting 1,1,1-trichlorotrifluoroethane (CFC-113a), available by isomerization of CFC-113 [44], to trifluoroacetic acid has been developed [45] (equation 45). It uses metal chloride catalysts deposited on high-surface-area supports Unreacted CFC-113a can be recycled. 

For most cases, common fluoroacyl derivatives are sufficiently reactive and selective Thus conversion of perfluoroglutaric dichloride to a monomethyl ester by methanol proceeds smoothly under the appropriate reaction conditions [17] (equation 9) Perfluorosuccinic acid monoester fluoride, on the other hand, is prepared most conveniently from perfluorobutyrolacetone [IS] (equation 10) Owing to the strong acidity of a fluonnated carboxylic acids, Fischer esterification with most aliphatic alcohols proceeds autocatalytically [79 20]... 

Fluonnated carboxylic anhydrides and acyl halides as common acylating reagents to convert amines to amides and to acylate suitable heterocyclic nitrogen atoms have already been described in the first edition [70] Like in the acylation at oxygen, much synthetic activity was concentrated in the past few years on the denvatization of biomolecules by fluoroacylation reacnons, that is, tnflmroacetylation of amino sugars,... 

Electrochemical fluonnation ot N,N dialkylammo-substituted carboxylic acids as their methyl esters produces the analogous perfluonnated tertiary amine carboxylic acid derivatives in 18-30% yields as well as cyclic amine ethers [JOO]... 

Carboxylic acids react with xenon difluoride to produce unstable xenon esters The esters decarboxylate to produce free radical intermediates, which undergo fluonnation or reaction with the solvent system Thus aliphatic acids decarboxylate to produce mainly fluoroalkanes or products from abstraction of hydrogen from the solvent Perfluoro acids decarboxylate in the presence of aromatic substrates to give perfluoroalkyl aromatics Aromatic and vinylic acids do not decarboxylate [91] (equation 51)... 

Pentafluorobenzyl bromide [II] and a partially fluonnated alkyl iodide [12] react with potassium carboxylates An interesting replacement of iodine in a fluonnated alkyl iodide by an acetate group takes place with peroxyacetic acid [13] (equations 10-12)... 

Fluonnated alkoxides, obtamed by addition of the fluonde anion to a carboxylic halide group, are weak nucleophiles, which can be alkylated [d5,36] (equanons 31 and 32)... 

When a hydrogen atom is present next to the carboxyl group, an intramolecular dehydration may occur, resulting in a ketene Two highly fluonnated, sulfur-con-taming ketenes were prepared this way [67, 84] (equations 54 and 55)... 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluonnation of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluonnation of octanoyl chloride results in perfluonnated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73], Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-AIkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

Vinyl acetates are also fluonnated by mixtures containing both acyl hy-pofluorite and perfluoroalkyl hypofluonte, obtained from fluorinatton of the carboxylic acid salts [16 /9] (equations 20 and 21)... 

One of the most useful ways of introducing fluorine into organic compounds is the replacement of the hydroxyl group in alcohols hydroxy compounds, and carboxylic acuis Methyl alcohol reacts with anhydrous hydrogen fluoride at 100 500 °C in the presence of aluminum fluoride [60, 61], zinc fluoride [62] chromium fluonde [63], or a mixture of aluminum and chromium fluorides [64] to give a 20-78% yield of fluoromethane Attempted fluonnations of higher alcohols by this method failed [60]... 

Furan-2-carboxylic add reacts with sulfur tetrafluoride at 0 °C to give 2-furoyl fluoride, but attempts at further fluonnation results in resin formation [222] A second carboxylic group and/or electron withdrawing substituents, such as the nitro or trifluoromethyl group, stabilize the furan ring Thus, turandicar-... 

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