Fluonnation enols

The enol ether formed by a reaction of benzyl alcohol with perfluorocyclo-pentene is transformed on heating in the presence of concentrated sulfunc acid into a fluonnated enol [25] (equation 22)... 

Selective fluonnation in polar solvents has proved commercially successful in the synthesis of 5 fluorouracil and its pyrimidine relatives, an extensive subject that will be discussed in another section Selective fluonnation of enolates [47], enols [48], and silyl enol ethers [49] resulted in preparation of a/phn-fluoro ketones, fieto-diketones, heta-ketoesters, and aldehydes The reactions of fluorine with these functionalities is most probably an addition to the ene followed by elimination of fluonde ion or hydrogen fluoride rather than a simple substitution In a similar vein, selective fluonnation of pyridmes to give 2-fluoropyridines was shown to proceed through pyridine difluondes [50]... 

Systems usually fluonnated by electropositive fluorine reagents include acti-vated alkenes (enol ethers, enol acetates, silyl enol ethers, and enamines), activated aromatic systems, certain slightly activated carbon-hydrogen bonds, and selected organometallics. 

Af-Fluorobis(trifluoromethanesulfonyl)imide is also effective in the mono-fluonnation of ester and amide enolates, and of neutral dicarbonyl compounds. Excellent stereoselectivity is observed [48, 80, 81] (equations 39-41)... 

Xenon difluoride reaction with nitro enolates provides a useful entry into a wide variety of fluonnated synthetic intermediates [91 92] (equation 52)... 

Silyl enol ethers are fluonnated in high yields with xenon difluoride [62 93, 94 95] Applications of this reaction to the preparation of fluonnated... 

The fluonnation of both mono and dinitro enolates proceeds well with perchloryl fluoride. The mononitro fluorinated intermediates have been used to develop fluorinated materials of general synthetic utility [III, 113] (equation 63)... 

Terminally unsaturated fluonnated alkenoic acids can be obtained from poly-fluorocycloalkenes by reaction with potassium hydroxide m rert-butyl alcohol [24] (equation 26) The use of a tertiary alcohol is critical because primary and secondar y alcohols lead to ethers of the cycloalkenes The use of a polar aprotic solvent such as diglyme generates enols of diketones [26] (equation 27) The compound where... 

Acyl hypofluorites react readily with enols, enol acetates, vinyl ethers, and enolates [39, 40, 41] (Table 2, entries 1-7) Steroidal enol acetates are also fluonnated smoothly [39] (equations 17-19)... 

Both enol acetates and enols are fluonnated by cesium fluoroxysulfate at room temperature in either acetonitrile or methylene chloride solutions (Table 2, entries 1,2 and 6)... 

Fluonnations of enolates with chiral reagent D (Table 3a) give moderate degrees of enantiomeric excess [67] (equation 43). 

Diacetato(l, 10-phenanthroline)palladium(II)-catalyzed transetherificatum of polyfluonnated alcohols with enol ethers leads to the corresponding fluonnated vinylic ethers [14] (equation 13)... 

The reactions of fluonnated esters and amides to form, respecuvely, enol ethers [47] and enamines [48] give high yields and are interesting synthetic transformations (equations 34 and 35) (Table 12)... 

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