Perfluoroacyl halides

Acyl fluorides have been used as intermediates to prepare fluoroethers from perfluoroacyl halides. Some of the perfluoroethers prepared are found to be not ozone-depleting and are therefore useful as detergents, solvents, heat-transfer media, etc.39... 

There are other sources of perfluoroalkyl radicals which have found occasional use, such as photolysis of hexafluoroacetone to generate trifluoromethyl radicals [75, 76], photolysis of perfluoroacyl halides [77], Umemoto s photolysis of... 

For acyl halides or anhydrides which do not afford ketenes in the presence of base (such as perfluoroacyl halides), however, the a-acylmethylenephosphoranes can be prepared directly in one step from the phosphonium salts by using two equivalents of base by the present procedure (Table I).2 Both tetrahydrofuran and methylene chloride have been used as solvents and in the case of the title compound, tetrahydrofuran provides the best results. Good yields of the phosphoranes are generally obtained when R1 is an electron-withdrawing group such as ester or nitrile. The yields of phosphoranes obtained for the thiomethyl or phenyl cases can be... 

Perfluoroacyl halides are reduced more easily than the corresponding perfluoroalkyl halides as shown by the data in Table 3. Electrochemical reduction of perfluoroacyl halides results in the formation of dimerization products although the yields of these processes are low (Eq. 11). ... 

Table 3. Reduction Potentials of Perfluoroacyl Halides RfCOX ...

The preparation of per- and poly-fluorinated carboxylic acids and their derivatives om the corresponding iodides is covered elsewhere (see pp. 47—48), and patents dealing with the conversions of trichloroacetyl chloride into trifluoroacetic acid and trifluoroacetyl chloride and the manufacture of chlorine-free anhydrous trifluoroacetic acid by hydrolysis of trifluoroacetyl chloride have been published. Treatment of sodium or silver perfluorocarboxylates with phosphorus(ni) difluoride halides or phosphorus(v) oxy- and thio-difluoride halides gives the corresponding perfluoroacyl halides in good yield (see Scheme 2) in certain cases the intermediate... 

Hydrosilation of ajS-unsaturated esters has been achieved using tris(triphenyl-phosphine)-chlororhodium as catalyst yields are excellent, and to a large extent the additions are regioselective, although the precise orientation of addition varies remarkably with the nature of the starting ester. Various perfluoro esters have been prepared directly from perfluoroacyl halides and organosilicon hydrides. ... 

Carbon monoxide evolution and formation of perfluoroalkyl derivatives directly is also observed when alkali metal salts of cobalt carbonyl are treated with perfluoroacyl halides or anhydrides at ambient temperatures (95,100, 101). 

Perfluoroacylbenzenesulfonic acids, RfC0C6H4S03H, or their salts [137] have been prepared by acylating benzene with a perfluoroacyl halide in the presence of a Lewis acid and sulfonating the reaction product. Sodium (perfluorooc-tanoyl)benzenesulfonate was prepared by reacting perfluorooctanoyl chloride with benzene in the presence of AICI3 ... 

Perfluoroacyl halides readily form perfluoroacyl-metal complexes, M—CORf, from which the perfluoroalkyl derivatives are easily prepared by decarbonylation, e.g. 

The title complexes are generally prepared by reaction of [Re(CO)s] (13) with organic halides (Scheme 11), affording a variety of alkyl, vinyl, acyl, aryl, and perflnoroalkyl and perfluoroacyl complexes. 

Although those Michaelis-Arbuzov reactions which involve acyl halides and phospho-rus(III) esters are yet a further route to phosphorus-carbon bond formation and will be discussed later in Section VI, the use of halogenated acyl halides has led to some unusual results which, conveniently, can be summarized here. The products obtained from reactions between trialkyl phosphites and perfluoroacyl chlorides contain both phosphonate and phosphate moieties and are structurally dependent on reaction temperature. The initial product (Scheme 4) is thought to be the ylide 66. In an ethereal solvent at low temperature, decomposition of the ylide yields [l-(dialkoxyphosphinoyl)oxy-l/f-perfluo-roalkyl]phosphonates (67) exclusively, but at -20 °C and above, and in the absence of a solvent, the products consist of (Z)-[l-(dialkoxyphosphinoyl)oxyperfluoroalkene]phos-phonates (68) . The treatment of the compounds 67 with Ida yields 68, and the action of BuLi-CuI on 68 results in loss of the phosphate moiety to give the esters 69 The structural isomers 70 of the compounds 68 have been obtained as illustrated in equation... 

The reaction between tris(trimethylsilyl) phosphite and a perfluoroacyl chloride proceeds without any apparent difficulty to give the predicted phosphonate diester 489 [R = Me3Si, R = CF3 or (CF3)2CH] but the use of longer chain polyfluorinated acyl halides or other heavily halogenated acyl chlorides leads to complications with such substrates, the initially formed acylphosphonate reacts with more phosphorus(III) ester to give the (Z)-enol phosphate 490 (Scheme 47). The halides, XCH2COX (X = Cl or Br) afford only the esters 491 (X = H). ... 

Mn(CO)5] reacts with allyl halides at room temperature to produce the hexacoordinate a-allyl derivative C3H5Mn(CO)5 which must be heated to 60° C before carbon monoxide is lost at an appreciable rate to form the ir-allyl derivative C3HsMn(CO)4 (99,100). In addition, the pentacoordinate perfluoroacyl derivatives of cobalt, RfCOCo(CO)4 (38, 111, 112), lose carbon monoxide to form RfCo(CO)4 at a lower temperature than the hexacoordinate perfluoroacyl derivatives of manganese, RfCOMn(CO)5 (38,113), form the perfluoroalkyl derivatives, RfMn(CO)s. On the basis of present data, however, it is diflicult to separate the effect of coordination number on the general stability of the molecule from the effect of coordination number on the stability of the metal-carbon monoxide bond. 

No stable compounds of the type R2Fe(CO)4 with iron-carbon a bonds have been isolated by the reaction between [Fe(CO)4] and alkyl halides such as methyl iodide. However, the perfluoroalkyl derivatives (Rf)2Fe (CO)4 (Rf = C2F5 and C3F7) have been obtained as air-stable very pale yellow crystals by the reaction between Na2[Fe(CO)4] prepared in tetra-hydrofuran and the perfluoroacy/ chlorides RfCOCl. The intermediate perfluoroacyl derivatives (RfCO)2Fe(CO)4 were not isolated, but instead were decarbonylated spontaneously in the boiling tetrahydrofuran 50). For reasons which are not clear at the present time the yields of the perfluoroalkyl compounds (Rf)2Fe(CO)4 in this reaction were only about 15%. Attempts to prepare (CF3)2Fe(CO)4 by this technique have been unsuccessful. A related compound is the extremely stable perfluorotetramethylene derivative C4FgFe(CO)4 (XXIX) 182) obtained from tetrafluoroethylene and iron pentacarbonyl. This fluorocarbon derivative was first erroneously formulated as a tricarbonyl derivative 183). 

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