Oxidation of fluoroalkyl

In addition, Ayari et aL [177] developed three methods by the oxidation of fluoroalkyl olefine with KMn04 and were able to improve significantly the yield of the synthesis of the fluorinated diols 12. 

A similar oxidative protocol has been used for the oxidation of (fluoroalkyl)alkanols, Rf(CH2) CH20H, to the respective aldehydes [146], in the one-pot selective oxidation/olefination of primary alcohols using the PhI(OAc)2-TEMPO system and stabilized phosphorus ylides [147] and in the chemo-enzymatic oxidation-hydrocyanation of 7,8-unsaturated alcohols [148]. Other [bis(acyloxy)iodo]arenes can be used instead of PhI(OAc)2 in the TEMPO-catalyzed oxidations, in particular the recyclable monomeric and the polymer-supported hypervalent iodine reagents (Chapter 5). Further modifications of this method include the use of polymer-supported TEMPO [151], fluorous-tagged TEMPO [152,153], ion-supported TEMPO [154] and TEMPO immobilized on silica [148],... 

To predict the stability of fluorinated polymers in the atmosphere polluted with nitrogen oxides, the ratio of rates of peroxynitrates in polytetrafluoroethylene (PTFE) by two mechanisms has been determined [19]. Chain peroxide radicals R 02 were obtained by photolysis of PTFE powder in a vacuum with the subsequent oxidation of fluoroalkyl macroradicals. The end peroxide radicals R 02 were generated by photolysis of the R 02 containing PTFE in the air. The exposure of PTFE samples containing chain or end peroxide macroradicals to NO2 results in decay of these radicals. The kinetics of the decay of peroxide radicals of both types is practically identical, and is likely to be determined by the rate of diffusion of NO into the... 

A hydroxyl group in the neighborhood of fluoroalkyl is oxidized by sodium dichromate to yield a ketone [481 (equation 44)... 

The synthesis of fluoroalkyl and chloroalkyl fluoromethyl ketones is achieved by oxidation of the corresponding alcohols by sodium dichromate and sulfunc acid in methylene chlonde in the presence of a phase transfer catalyst [49] (equation 45)... 

Anodic Oxidation of Heteroatom Compounds Having Fluoroalkyl Groups... 

Table 4. Oxidation potentials (peak potentials, Ep) of fluoroalkyl chalcogeno compounds ...

This chapter does not attempt to cover electrochemical processes which involve the insertion of a group already containing carbon-fluorine bonds into an existing molecule (the building block approach), e.g., perfluoroalkyl group insertion via the Kolbe reaction, or fluoroacyloxylations or fluoroalkoxylations via electro-oxidation, or fluoroalkylation via electro-reduction. These have been reviewed elsewhere [1,2]. 

The aerial oxidation of solutions of complexes (330) has been investigated. Chromatography separation led to the identification of products which underwent dehydrogenation of the ethylene bridge (Scheme 31).2413 Such dehydrogenation reactions are inhibited by fluoroalkyl substituents and enhanced by alkyl substituents. Oxidation with hydrogen peroxide removes the ethylene bridge. 

Bis(fluoroalkyl) and tris(lluoroalkyl) phosphites arc oxidized to the corresponding phosphates using a mixture of oxygen with nitrogen dioxide.277,278 In the oxidation of tris(2,2,3.3-tetrafluoropropyl) phosphite (5) by oxygen, bromal exhibits a strong catalytic effect, while chloral is less effective.278... 

Fluoroalkyl iodides are oxidized at the iodine atom by trifluoroperacetic acid3 7- 19 or by a mixture of trifluoroacetic anhydride with hydrogen peroxide the products are [bis(trifluoro-acetoxy)iodo]fluoroalkanes, e.g. oxidation of 1 to 2. The iodine atom oxidized in the reactions can be attached either to a nonfluorinated317 318 or a fluorinated carbon atom.319... 

Similar to the Dakin-West procedure previously mentioned, the Henry nitro-aldol condensation reaction is most widely used to synthesize trifluoromethyl ketones, although there are many examples of a,a-difluoroalkyl ketones synthesized by this method (Table 6)JU 12271 The method for a,a-difluoroalkyl and trifluoromethyl ketone synthesis is identical except for the final oxidation although fluoroalkyl and a,a-difluoroalkyl ketones are easily oxidized by the Sarett method (Cr03/pyridine),[12 the corresponding trifluoromethyl ketones can only be oxidized under basic conditions (0.3 M NaOH) with KMn04Jul Also, in some of the syntheses of a,a-difluoroalkyl ketones, the nitro alcohol intermediate was protected by si-lylation with /ert-butylchlorodimethylsilane. The silyl group was later removed by TosOH prior to oxidation. The full details of this method are given in Section 15.1.4.3.2. 

An experimental and theoretical study of the Baeyer-Villiger (BV) oxidation of ketones has examined its uncatalysed and acid-catalysed forms, and fluoro- and chloro-substituted substrates.344 In assessing migratory aptitudes, fluoroalkyl groups are only slightly less favourable than alkyl (by 0.3/0.5 kcal mol-1, calculated/observed), whereas migration of a chlorinated substituent is significantly more difficult (ca 2.6 kcal mol-1). 

Pyrroles, furans, and thiophenes react preferentially with radicals at the 2-position. Thus, reaction of pyrrole with benzyl radicals gives 2-benzylpyrrole. In rather better yields, pyrrole and indole treated with per(poly)fluoroalkyl chlorides (RfCI) in the presence of sodium dithionite in DMSO produce 2-perfluoroalkyl products <2001JFC(111) 107>. Furans trap aryl radicals, generated from the Mn(OAc)3 oxidation of arylboronic acids <2003JOC578> or... 

The present procedure is based on the use of fluoroalkyl alcohols as solvents in oxidation reactions. The method is efficient and versatile, and produces disulfides and sulfoxides under mild conditions. These reactions have also been developed using hexafluoroisopropyl alcohol (HFIP) as solvent with a large variety of substrates (alkyl sulfides, alkyl thiols, vinyl sulfides, fiuorinated vinyl sulfides, thioglucosides) by Begue et al."> Replacement of HFIP with trifluoroethanol, a more common and less expensive solvent, also allows the use of mild conditions and affords high yields of disulfides and sulfoxides without contamination. 30% Aqueous hydrogen peroxide is inexpensive and, since water is the sole byproduct, this method is environmentally friendly. 

Sulfonylation. The iodine atom of fluoroalkyl iodides suffers oxidation and is then replaced by a sulfonic acid group on reaction with Na2S20s. On further treatment with chlorine and then with KF the sulfonyl fluorides are readily synthesized. 

Electrochemical Synthesis of Fluoroalkylated Sulfenimines. 83 Anodic Oxidation of Trifluoromethylated Carboxylic... 

ANODIC OXIDATION OF HETEROATOM COMPOUNDS CONTAINING FLUOROALKYL CROUPS... 

Table 5. Oxidation Potentials (Peak Potentials, fp) of Fluoroalkyl Chalcogeno Compounds ...

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