Hypofluorites and

Fluoroxytrifluoromethane (trifluoromethyl hypofluorite) and acetyl hypofluorite are the most commonly used neutral hypofluontes, cesium fluoroxysultate is an inorganic anionic fluoroxy derivative... 

As has been exemplified in this chapter, fluorinations with fluorine-18 can be classified into two categories (1) the nucleophilic reactions, which usually involve no-carrier-added [ F]fluoride of high-specific radioactivity as its Kf FIF-K complex and include substitutions in the aliphatic and the /lomoaromatic series and (2) the electrophilic reactions, which mainly use moderately low-specific radioactivity molecular [ F]fluorine, or other reagents prepared from it, such as acetyl [ F] hypofluorite, and include addition across double bonds, reactions with carbanions and especially fluorodehydrogenation and fluorodemetallation reactions. 

Trifluoromethyl hypofluorite was first made by Cady by passing methanol [184] or carbon monoxide [185, 186] with fluorine over silver difluoride at elevated temperatures. Later, trifluoromethyl hypofluorite and higher perfluoroalkyl hypofluorites were prepared by treating the appropriate carbonyl compound with fluorine in the presence of dry caesium fluoride at sub-zero temperatures (Fig. 81) [187-189]. 

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. 

In this section we will discuss the use of elemental fluorine for the promotion of organic transformations that do not result in the introduction of fluorine into the substrate. As we described above (Sect. 3), fluorine may be used to prepare many extremely useful reagents which may be employed as, for example, oxidising and oxygen transfer agents. The use of O-F compounds, such as acetyl hypofluorite and the HOF.MeCN complex, in functionalisation processes has been indicated above (Sect. 3.2), and this area has been discussed in detail in an excellent account by Rozen [19]. 

C1F 54.46 - 155.6/- 100.1 + + + + also usable for synthesis of hypofluorites and oxidative S- or Se-fluorinations of organic sulfur and selenium compounds, frequently in situ preparation of the agent from A -chloro-substituted amides and HF, HF-containing systems or AgF 4, 7... 

Reactions with Methyl Hypofluorite and ferf-Butyi Hypofluorite... 

Enol acetates, oxo esters, nilroalkenes33 and sodium salts of various esters have been successfully converted into fluoro ketones and esters by acetyl hypofluorite, trifluoroacetyl hypofluorite or mixtures containing acetyl hypofluorite and fluoroxy compounds.3 4 -10-12-13 Examples are the formation of l-fluoro-l,3-diphenylacetone (12), a-fluoro-/i-oxo esters 13, a-fluoro ketones 14 and 15. ethyl l-fluoro-2-oxocyclopentanecarboxylate (16), and 2-fluoromalonate 17. 

Various steroids can be fluorinated, to provide vicinal fluoro acetates with predominant or exclusive syn addition, with acetyl hypofluorite or a mixture of acetyl hypofluorite and fluoroxy compounds,4"10 e.g. reaction of 18 and 19. 

Various uracil, cytosine and pyrimidine nucleosides, e.g. 22, have been successfully fluorinated by acetyl hypofluorite and also some labeled I8F derivatives synthesized.16- 18 34... 

Reactions with acetylenes have been much less intensively studied, but important and large differences between trifluoromethyl hypofluorite and trifluoroacetyl hypofluorite have been observed.2 An example of the reactivity of trifluoroacetyl hypofluorite with acetylenes is given by the reaction with 1,2-diphenylacetylene (23) acetyl hypofluorite is unreactive even at room temperature.10... 

These esters of nitric acid form one of the two groups of nitrates, the covalent group, which are also exemplified by nitryl hypofluorite and... 

Aromatic systems arc fluorinated by reagents containing an O-F bond, in particular by tri-fluoromethyl hypofluorite, and acetyl hypofluoritc. Trifluoromethyl hypofluorite is a commercial reagent which is prepared by the reaction of elemental fluorine with carbon monoxide. The initial product is carbonyl fluoride 10 formed by a spontaneous and highly exothermic reaction. This product is passed through a bed of cesium fluoride which catalyzes the addition of a second mole of fluorine to give trifluoromethyl hypofluorite. 

Acetyl hypofluorite will only fluorinate activated aromatic compounds and fluorinations arc generally performed at low temperatures. In general a mixture of products is formed, for example, the fluorination of anisole with acetyl hypofluorite results in a mixture of 2-fliioroanisole and 4-fluoroanisole (ratio 9.6 1) in 85% yield (Table 11). This preferential formation of the ortho-Komcr is explained by an addition-elimination mechanism with an intermediate 15. This mechanism is support by the fact that the addition product 16 from acetyl hypofluorite and pipcronal is isolated in 55 % yield. Selective fluorination is achieved when the para position is blocked by a second substituent (Table 12). This approach has been used to selectively fluorinate an aromatic ring in peptide 17. " ... 

Fluorination of aryltrimethylsilanes with xenon difluoride is a method for the synthesis of F-labelcd eompounds, since [ F]XeF2 be prepared. F-Labeled aryl fluorides are also prepared by reaction of aryltrimethylsilanes with F-labeled acetyl hypofluorite and elemental fluorine. ... 

Pentafluoroethoxy Tellurium Pentafluoride Into a 30 ml stainless steel Hook cylinder cooled to —196° are condensed in succession from a vacuum line 0.366 g (1.42 mmol) of pentafluorotellurium hypofluorite and 0.230 g (2.30 mmol) of tetrafluoroethene. The cylinder is sealed and slowly allowed to warm to 20° in a cold, empty Dewar vessel or in one partly filled with dry ice. After 48 h, the cylinder is recooled to — 196° and any noncondensable gases are removed. The cylinder is again warmed to 20° and the gases arc allowed to pass through a series of three traps kept at temperatures above —112°,at —112°,and below —112°. The product condenses in the —112" trap and is purified by an additional trap-to-trap distillation yield 0.30 g (60%) Similarly obtained (trapping temperature given) were ... 

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