Acyl fluorides hydrogenation

Hydrogen fluoride, HP, when used alone is a comparatively ineffective exchange agent and replaces only active halogens (13), eg, acyl fluorides from acyl chlorides and ben2otrifluoride [98-08-8] from hen2otrich1 oride (eq. 12). 

Pubhcations have described the use of HFPO to prepare acyl fluorides (53), fluoroketones (54), fluorinated heterocycles (55), as well as serving as a source of difluorocarbene for the synthesis of numerous cycHc and acycHc compounds (56). The isomerization of HFPO to hexafluoroacetone by hydrogen fluoride has been used as part of a one-pot synthesis of bisphenol AF (57). HFPO has been used as the starting material for the preparation of optically active perfluorinated acids (58). The nmr spectmm of HFPO is given in Reference 59. The molecular stmcture of HFPO has been deterrnined by gas-phase electron diffraction (13). 

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 fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated 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-Alkyl-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... 

Replacement of a hydrogen with bromine in the polyfluoroalkyl group of a ketone or acyl fluoride can be carried out with phosphorus pentabromide [i50] (equation 45)... 

Rearrangement of fluorine with concomitant ring opening takes place in fluorinated epoxides Hexafluoroacetone can be prepared easily from perfluo-ropropylene oxide by isomerization with a fluorinated catalyst like alumina pre treated with hydrogen fluoride [26, 27, 28] In ring-opening reactions of epoxides, the distribution of products, ketone versus acyl fluoride, depends on the catalyst [29] (equation 7) When cesium, potassium, or silver fluoride are used as catalysts, dimenc products also are formed [29]... 

Hydrolysis of acyl halides is not usually catalyzed by acids, except for acyl fluorides, where hydrogen bonding can assist in the removal of There are several methods available for the hydrolysis of acyl fluorides. ... 

Naming structure 9 pcrfluorobutanal nicely illustrates the important rule (quoted earlier) that hydrogen atoms forming part of a functional group remain unsubstituted by fluorine (structure 10 is, of course, an acyl fluoride) likewise perfluoropropanoic acid is 5 not 11 (an acyl hypo-fluorite), while perfluoropiperidine is 12 not 13 (perfluoro-l-fluoropiperidine). 

Acyl chlorides (or anhydrides) react in 70% hydrogen fluoride/pyridine to give acyl fluorides in high yields31 (for HF/melamine, see ref 248). 

Furthermore, the cleavage of organic sulfites and sulfates by hydrogen fluoride gives the corresponding alkyl or acyl fluorides in fair to good yield,287 e.g. formation of acetyl fluoride from the mixed anhydride287 or sulfonyl fluorides from sulfonic acid anhydrides.287... 

Methyl perfluoromethacrylate reacts with allyl and propargyl alcohols to give the Michael addition products 19 and 20, respectively these eliminate hydrogen fluoride in the presence of the boron trifluoride-triethylamine complex and rearrange to acyl fluorides 21 and 22. Hydrolysis of the acyl fluorides with base results in decarboxylation to give the 2-(trifluoromethyl) esters 23 and 24.11... 

Polyfluoro-/f-sultones 3 isomerize in the presence of nucleophilic catalysts to polyfluorinaied a-fluorosulfonyl acyl fluorides 4.45 47 The nucleophilic catalysts include triethylamine,45 ammonia,48 dioxane,49,50 dibutyl ether,49,50 and alkali metal fluorides.46 The reaction has been carried out thermally and in the presence of liquid hydrogen fluoride.50... 

Compounds which tend to eliminate hydrogen fluoride in the presence of a base are 1.2-difluoroalkancs, oqa -difluoro ethers, a,a -difluoro sulfides, /1-fluorocarbony] compounds, 1,1-diaryl- and 1,2-diarylpolyfluoroalkanes, 277-acyl fluorides and polyfluoroalkylammonium salts. Polyfluoroalkancs (see Table 2) are relatively labile towards basic reagents. If two elimination pathways are possible, such as in 1,1,2.3,3,3-hexafluoropropanc (1), hydrogen is eliminated from the carbon bearing fewer fluorines.11,2... 

Likewise open-chain, cyclic five- and six-memhered a,a,a, a tetrafluoro-ethers are opened by anhydrous hydrogen fluoride at elevated temperatures to give acyl fluorides terminated with a trifluoromethyl group A six-inembered ether such... 

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... 

One fluorine atom is leaving as a fluoride ion, and the exocylic double bond to the difluoromethylene group is attacked by a hydroxide anion. Elimination of hydrogen fluoride gives an acyl fluoride that is readily hydrolyzed to the final product, 2-amino-4-trifluoromethylbenzoic acid (K) [59],... 

The double bond is easily hydrated. Elimination of hydrogen fluoride yields an acyl fluoride which is ultimately hydrolyzed to E, 2-fluoro-3-methylbuten-2-oic acid [111]. 

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