Alkyl Hypofluorites

When fluorine is passed through a mixture of methanol in acetonitrile at -45 °C or propionitrile at -75 °C a solution of methyl hypofluorite, stabilised by the solvent, is produced [200]. While methyl hypofluorite can be isolated, its chemistry has been investigated by treating various substrates with freshly prepared solutions rather than with isolated material. Unlike the hypofluorites which have been discussed so far, methyl hypofluorite behaves as a synthon for the rare methoxylium species, MeO+ , and adds to various alkenes electrophilically in accordance with Markovnikov s Rule [201]. In the reaction between methyl hypofluorite and indene, almost exclusive trans addition occurred. 

Hypofluorous acid decomposes very rapidly above -100 °C but, by passing fluorine through aqueous acetonitrile, a complex of HOF with acetonitrile is formed which is stable for several hours at room temperature. The chemistry of this interesting reagent has been reviewed recently [6,19,199]. 

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Appelman, E. etal., J. Amer. Chem. Soc., 1991,113(7), 2648 This compound, the first known alkyl hypofluorite, was found to be stable but reactive at -120°C, but samples sometimes exploded on warming to cardice temperatures (—80°C ). 

Low-temperature fluorination of sodium acetate in suspension gives a mixture of acetyl hypo-fluorite (AcOF, 1, R = Me) and alkyl hypofluorite the crude mixture can be used, in some cases, directly for the introduction of fluorine into organic molecules. The course of the reaction strongly depends on the reaction conditions and, when the fluoride anion is quenched with hydrogen fluoride or water, trifluoroacetyl hypofluorite (1, R = CF3), 3 acetyl hypofluorite (1, R = Me) and long-chain acid fluorites are obtained.4-6 On the other hand, an excess of fluorine can lead to the formation of alkyl fluoroxy compounds 2 or geminal bis(fluoroxy) products 3. 

Nonfluorinated alkyl hypofluorites (ROF) are mostly unstable and decompose through HF elimination with formation of the corresponding carbonyl compounds. However, tert-butyl [24] and methyl hypofluorites (RO+ F ) [25] can be generated and employed in situ for alkoxy-fluorination of alkenes. The relatively higher stability of both hypofluorites comes from the nonavailability of a-hydrogens which are reactive to the radical hydrogen abstraction [26]. Both of the hypofluorites add to carbon-carbon double bonds regio- and stereoselectively as shown in Scheme 2.48. The anti-addition mode (37-39) is in sharp contrast to the syn-addition mode of electrophilic fluoroalkoxy and acetoxy reactions of fluorinated alkyl and acetyl hypofluorites (RfO F+, 40-41) [27]. 

The addition of f-BuOF stands in contrast to the pattern of reaction of other alkyl hypofluorites, such as CF3OF and CF3CF2OF, since they add in a syn process and with the opposite regiochemistry for fluorine addition Lerman, O. Rozen, S. /. Org. Chem. 1980, 45, 4122 Rozen, S. Lerman, O. Kol, M. Hebei, D. /. Org. Chem. 1985,50,4753. 

Tetrafluoroammonium hexafluoromanganate, 4378 Tetrafluoroammonium hexafluoronickelate, 4379 Tetrafluoroammonium hexafluoroxenate, 4380 Tetranitromethane, 0543 Titanium tetraperchlorate, 4164 1,1,1 -Triacetoxy-1,2-benziodoxol-3-one, 3604 Trifluoromethyl hypofluorite, 0352 Trimethylsilyl chlorochromate, 1297 Trioxygen difluoride , 4317 Uranium hexafluoride, 4369 Vanadium trinitrate oxide, 4758 Vanadium(V) oxide, 4860 Vanadyl perchlorate, 4146 Xenon hexafluoride, 4371 Xenon tetrafluoride, 4347 Xenon tetrafluoride oxide, 4340 Xenon tetraoxide, 4857 Xenon trioxide, 4851 Xenon(II) pentafluoroorthoselenate, 4376 Xenon(II) pentafluoroorthotellurate, 4377 Zinc permanganate, 4705 ACETYLENIC PEROXIDES ACYL HYPOHALITES ALKYL HYDROPEROXIDES ALKYL TRIALKYLLEAD PEROXIDES AMINIUM IODATES AND PERIODATES AMMINECHROMIUM PEROXOCOMPLEXES BIS (FLUOROOXY)PERHALOALKANES BLEACHING POWDER CHLORITE SALTS... 

Chloropyridines (and other halogenopyridines) can be made by the action of acetyl hypofluorite in the presence of an appropriate alkyl halide on pyridine. The strategy employed here is to attack the basic pyridine nitrogen with a strong electrophile in order to decrease its mesomeric back donation. Electrophilic fluorine is a suitable candidate for this task. Effectively, acetyl hypofluorite adds across the C=N bond. 

It has been known that highly fluorinated alkyl-hypochlorites and hypofluorites RFOX (with X=C1 or F) are of synthetic value in the preparation of many fluorine... 

Until recently it was assumed that all fluoroxy compounds must have a perfluorinated alkyl chain, otherwise HF elimination would take place immediately. While this line of reasoning is valid to some extent, it is by no means a general rule. The most notable exception is acetyl hypofluorite (CH3COOF). 

FLUORINATION Acetyl hypofluorite. Carbonyl difluoride. N-Fluoro-N-alkyl-p-tolu-enesulfonamides. 

Until recently the carbon skeletons to which the O-F moiety was attached contained no hydrogens and practically always consisted of a perfluoro alkyl group. It was assumed that a hydrogen would trigger an immediate decomposition through an easy HF elimination. A few years ago we showed that there are some exceptions to this "well known fact". We prepared, for the first time, acetyl hypofluorite - AcOF - by reacting sodium acetate with... 

Trifluoromethyl hypofluorite reacts with a variety of aromatic systems, with the ease and extent of substitution dependent on the nature of the substituent already present. At low conversion (41%). benzene is converted into a mixture of fluorobenzene (93%) and (tri-fluoromethoxy)benzene (5 %) when the conversion is increased, multifluorinated products become significant impurities. The fluorinations of aromatics containing alkyl substituents, e.g. toluene, with trifluoromethyl hypofluorite yield complex mixtures of products with poor material balance. A-Substitutcd aniline derivatives 11 react with trifluoromethyl hypofluorite to give high yields of ortho- and /wra-monosubstituted fluoro derivatives. 

Alkyl and aryl difluorosulphuranes are readily obtained by treatment of corresponding sulphides with trifluoromethyl hypofluorite. Tetrafluoro-analogues R2SF4 are obtained in some cases, and perfluoroalkyl derivatives RSF4CI are described. ... 

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