Fluoroxy compounds

Application of Fluoroxy Compounds to Organic Synthesis Electrophilic PHiiorination of Unsamrated Molecules Hesse, R. H Isr. J Chem 17, 60-70 43... 

Although fluonnation of peroxoanions [S2] has been examined, the major emphasis in the fluonnation of oxygenated material is the preparation offhioroxy compounds The simplest, trifluoromethyl hypofluorite, can be prepared almost quantitatively by the action of fluorine on carbonyl fluoride (fluorophosgene) in the presence of various catalysts [Si, 84] Addition of fluorine to trifluoroacetic acid [S5] or its sodium salt [S6] gives rise to FjCF(OF)2 Long-chain fluoroxy compounds can also... 

While fluoroxy compounds react well with enol derivatives, fluorine in general does not. However, there are various reports where such reactions are described and in certain cases even with decent yields. In 1982 it was reported that pyruvates with a dominant enolic form react well with fluorine, to give the corresponding fluoro derivatives l.78 Several silyl enol ethers 2 and 379 including ones made from 1,3-dicarbonyl derivatives 480 react quite satisfactorily with fluorine to give the expected a-fluoro ketones. Steroidal 16-enol acetates react with fluorine to form mainly 16a-fluoro-17-oxo steroids e.g. 5.81... 

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. 

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. 

Johri and DesMarteau [41] have previously claimed that such reactions underwent a free radical mechanism. Actually, the radical mechanism was demonstrated by Di Loreto and Czarnowski [50], the polyfluoroalkyl fluoroxy compound being usually broken homolytically producing RfO and X radicals in the initiation step, as presented in Scheme 1. 

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). 

When functional groups are present, the products can be quite complex. Primary and secondary amines give NF2 and NF compounds respectively and fluorination of sulphur compounds gives products in which the sulphur has been oxidised to its maximum valency state of six [149] (Table 2.4). Hydroxy compounds can give fluoroalkyl hypo-fluorites (fluoroxy compounds) (see also Chapter 3, Section IIIB), the corresponding alkyl derivatives not being stable [150, 151] bisfluoroxy derivatives have also been isolated [152-154] (Figure 2.27). 

A variety of compounds has been used as halogenation agents [3]. Fluorination can be performed with molecular fluorine (F2), HF, fluoroxy compounds, XeFi, perchloryl fluoride (FCIO3) and metallic fluorides (especially CrF3 and AIF3 or their mixtures). Apart from molecular chlorine and HCl, other popular chlorina-... 

Addition Reactions.—Electrophilic fluorination by fluoroxytrifluoromethane (CF3OF) has now been extended to a series of fluoroxy-compounds [(CFjljCOF, (CF3)2(C2F5)C0F, SF5OF, and CF2(OF)2 ], allowing the conversion, for example,... 

In a previous study on the use of fluoroxytrifluoromethane (CF3 OF) as an electrophilic fluorinating agent, it was suggested that fluoroxy-compounds as a class might be disposed to undergo nucleophilic attack at fluorine. This hypothesis... 

Fluorination of aromatics is conveniently achieved by using fluoroxy compounds, e.g., FOCF3 (12, 13). The fluorine in these reagents is a very soft acceptor. 

John specialized in fluorine, boron, sulfur, phosphorus, and metal carbonyl chemistry. With M. Frederick Hawthorne, he discovered a series of amine complexes of aluminum trihydride and showed that some of them give aluminum metal when heated this process later became useful for the formation of aluminum thin films by chemical vapor deposition. One of his notable achievements was the discovery that the PPN cation, bisftriphenylphosphoranyhdene) ammonium, forms air-stable salts with many air-sensitive anions such as [Co(CO)4] . He also discovered that cesium fluoride can serve as a catalyst for the synthesis of organic fluoroxy compounds (RpOF) by the fluorination of acyl halides. 

Several different types of fluoroxy-compound have been shown to behave as electrophilic fluorinating agents, the best being bis(fluoroxy)difluoro-methane free radicals are not involved. Phenyltetrafluorophosphorane is recommended as a selective fluorinating agent for alcohols (Scheme 135). 

An improved method of synthesis of fluoroxypentafluoroselenium SeFs-OF has been developed, viz. direct fluorination of the solid (KSeOFj ) formed by the addition of potassium fluoride to seleninyl fluoride. Treatment of the fluoroxy-compound with perfluorocyclopentene, carbon monoxide, and sulphur tetrafluoride has yielded the new compounds cyclo-CsF -O-SeF, SeFs O COF, and SeFs-O SFj, respectively. 

Barton, D. H. R., L. J. Danks, A. K. Ganguly, R. H. Hesse, G. Tarzia, and M. M. Pechet Organic Reactions of Fluoroxy-compounds Addition Reactions of Unactivated and Deactivated Unsaturated Linkages of Steroids. Chem. Commun. 1969, 227. 

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