Fluorinations alkenes, silver® fluoride

There are only a few examples of the addition of fluorine to halogenated alkenes using silver(II) fluoride in the literature. Two examples 16 and 17 are given. ... 

Fluorine can also be added to alkenes by reaction with a solution of anhydrous hydrogen fluoride in pyridine (Olah s reagent) containing either Af-brotno- or A -iodosuccinimide, or iodine or bromine and silver nitrate. The final addition of silver fluoride to the reaetion mixture leads to the formation of vicinal difluorides 19,23.153... 

Silver fluoride adds to electron deficient alkenes. The reaction of l,l-dichloro-2,2-dicyanoethylene with AgF, for example, does not produce the expected 1,1-difluoro derivative. Instead, this reaction yields the silver salt of trifluoromethylmalononitrile, presumably through the 1,1-difluoro derivative by subsequent addition of AgF to the strongly electrophilic double bond. Perfluo-roalkylsilver compounds can be prepared by the addition of AgF to perfluoroalkenes. The fluorination of tetrabromo-2,3-diaza-1,3-butadiene affords the tetrafluoro derivative. 

Fluorinated organometallics can be prepared by the direct addition of metal fluorides across the double bond of fluorinated alkenes. Additions of mercury(II) fluoride, ar-senic(III) fluoride " and silver(I) fluoride " " have been reported (sec Table 35). These reactions are catalyzed by hydrogen fluoride. arsenic(III) fluoride or antimony(V) fluoride. 

The simultaneous addition of iodine and fluorine to cyclohexene leads to frrw.v-l-fluoro-2-iodocyclohe.xanc. The use of different reagents has been described, for example silver(I) fluoride/ iodine184 1 17 224-278 (yield 52-64%), hydrogen fluoride/A -iodosuecinimide217-220 221-274 284 (yield 52-75%), fluorine/iodine223 227 (yield 64%) and bis(pyridine)iodonium tetrafluoro-borate/tetrafluoroboric acid219 (yield 89%). Some further examples of the simultaneous addition of iodine and fluorine to cyclic alkenes are listed in Table 25. 

Dimerization of alkanes can be brought about by the irradiation of zeolite-Y with added silver atoms and silver clusters lead to dimerization on irradiation at 220-300 nm . Selective fluorination of di- and triphenyl methane in acetonitrile as solvent and Ti02 as catalyst can be effected using AgF. Di- and triphenylacetic acid as well as alkenes can be fluorinated in the same way. A single electron transfer reaction is thought to be involved, followed by attack of fluoride . It could be that the reaction is one that arises on the 1102 surface and that the Ag+, to which the electron transfer could take place, is not involved . 

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