Fluonnation enols, enolates, enol ethers

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. 

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

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)... 

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)... 

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)... 

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... 

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