Fluonnation fluoro compounds

The anions of malonaldehyde [106, 107] and of organophosphonates [108, 109, 110] are fluorinated in good yields to provide interesting fluorinated intermediates The At-fluoro compound B in Table 3a is also effective in the fluonnation of phosphonate anions [109] (equations 60 and 61). 

Extensive reviews of the effects of fluonnation on stmeture and bonding are available [75, 76, 77], and only the charactenstic trends in bond strengths will be covered here. The bond energies cited are average values corrected for the revised heats of formation of alkyl radicals [78], but their precision is seldom better than 2 kcal/mol for the fluoro compounds. 

Mmy fluonnated aromatic compounds are alkylated with alkyl halides under Fnedel-Crafts conditions For example, the intramolecular alkylation of 3-fluoro-A-(chloroace-tyl)amhne with aluminum chlonde gives 6-fluorooxmdole [5] (equation 5) Similarly, 3 -chloro-4-fluoropropiophenone affords 5-fluoroindanone [6] (equation 6)... 

On the other hand, as a result of participation of a neighboring group, complete or predominant retention of configuration takes place in many reactions of hy-droxylic compounds with DAST A number of examples have been reported in the field of steroids [727,129], in the conversion of vitamins D into fluoro vitamins D [145], and in the fluonnation of liquid crystals [146] (equation 72)... 

A more efficient agent than peroxy compounds for the epoxidation of fluoro-oletins with nonfluonnated double bond is the hypofluorous acid-acetonitrile complex [22] Perfluoroalkylethenes react with this agent at room temperature within 2-3 h with moderate yields (equation 13), whereas olefins with strongly electron-deficient double bond or electron-poor, stencally hindered olefins, for example l,2-bis(perfluorobutyl)ethene and perfluoro-(l-allcylethyl)ethenes, are practically inert [22] Epoxidation of a mixture of 3 perfluoroalkyl-1-propenes at 0 °C is finished after 10 min in 80% yield [22] The tnfluorovinyl group in partially fluonnated dienes is not affected by this agent [22] (equation 13)... 

This technique has been applied to the synthesis of fluonnated dopamine and other compounds of biological significance Fluoroheterocycles such as fluoro-imidazoles [75, 76] and fluoropyrazoles [77] can also be prepared by the photo Balz-Schiemann technique (equation 9) Photochemically induced in situ fluoro dediazoniation can also be applied to arenediazonium fluorides in hydrogen fluo nde-pyndine media Thus, o-fluoroanisole is obtained in 73% yield at 20 °C after 18h [75]... 

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