Xenon difluoride with alkenes

The interaction of alkenes with xenon difluoride has been successful in the presence of a catalyst. Dec-l-ene treated with xenon difluoride in the presence of a boron trifluoride-diethyl ether complex in dichloromethane formed 1,1-difluorodecane (26%) and a mixture of 1-fluoro-decene isomers (48%). Under the same conditions 2-fluoro-2,2-dinitroethyl vinyl ether has been converted to T,2 -difluoroethyl-2-fluoro-2,2-dinitrocthyl ether.27... 

Table 11 summarizes the results from Zupan and Poliak on the fluorination of phenyl-substituted alkenes with xenon difluoride. 

Table 11. Fluorination of Phenyl-Substituted Alkenes with Xenon Difluoride...

Phenyl-substituted alkenes with halogen atoms at the double bond react with xenon difluoride in dichloromethane in the presence of hydrogen fluoride forming vicinal difluorides in 50% yield.35... 

Alkenes react with xenon difluoride in the presence of some auxiliary reagent to form unsymmetrical addition products. Treatment of indene (8) with xenon difluoridc and methanol in the presence of hydrogen fluoride leads to fluoromethoxylation of the C = C bond, dia-stereomers of 1-alkoxy-2-fluoroindane are formed as the major product, difluoroindane was detected in trace quantities. In the presence of a boron trifluoride-diethyl ether complex the crossover l-fluoro-2-alkoxylated indanes have been obtained as major products.48,49... 

Alkenes react with xenon difluoride and diphenyldiselcnide to give the corresponding products of 1,2-fluoroselenation. Formation of phcnylselenyl fluoride as the unstable intermediate has been postulated. Cyclohexene (9) has been treated with xenon difluoride and diphcnyl-diselenide in dichloromethane at — 20 C to form tran.v-l-fluoro-2-phenylselenocyclohexane (10) in 73% yield. 2-Phenylselcnocyclohexanol (11) is the major byproduct in 5% yield due to the hydrolytic instability of the fluoroselenide 10. 

Vinyltrimethylstannanes react with xenon difluoride in dichloromethane at room temperature in the presence of equimolar (or a 50 Vo excess) of silver trifluoromethanesulfonate and a catalytical (0.1 equiv) quantity of 2,6-di-/e/7-butyl-4-methylpyridine to form the corresponding vinyl fluorides in high to moderate yields.54 57 The substitution reaction is tolerant to various functional groups, such as ketones, esters, carbamates, ketals, ethers, phenol rings and tertiary alcohols. As byproducts corresponding alkenes have been detected due to pro-tiodestannylation. 

To overcome problems associated with the removal of iodobenzene and its derivatives formed upon fluorination of arylalkenes and arylalkynes with (difluoroiodo)arenes, polymer-supported (difluoroiodo)arenes were proposed.139 With these agents, the separation procedures are reduced to filtration of the iodinated polymer. For this purpose popcorn polystyrene is io-dinated and then transformed into the difluoroiodide by treatment with xenon difluoride in the presence of hydrogen fluoride in dichloromelhane at 25 C. The amount of active fluorine bonded to iodine atoms on the polymer support is estimated by iodometric titration. The reactions with phenyl-substituted alkenes result in rearranged gew-difluorides. The procedure provides the same fluorination products as with (difluoroiodo)benzenc (see Section 4.13.) but in much higher yields, e.g. PhCF2CH2Ph (96%), PhCF2CH(Me)Ph (95%). PhCH2CF2H (86%), and l,l-difluoro-2-phenylcyclopentanc (91 %). 

Treatment of vinyllin compounds with xenon difluoride in dichloromethane at 25"C results in low yields of the desired vinyl fluorides with the major products being the corresponding alkenes. In addition to the poor yield of the desired compound the reaction times are long (2-3 d). Attempts to increase the reactivity of the vinyltin compounds by the addition of... 

Polymer-bound phenyliodine difluoride, which also has been used as a reagent to add fluorine to alkenes, can be prepared by the addition of xenon difluoride to the polymer [134, 135 136] Methyl iodide is converted to trifluoro methyliodine difluoride by treatment with fluorine at -110 C [137] Perfluoro-alkyliodine tetrafluorides could be synthesized from the perfluoroalkyliodine difluorides and fluorine [138] or chlorine trifluoride [139] Perfluoroalkyl [140] and perfluoroaryl [141] iodides are oxidized to the corresponding iodine difluorides by chlorine trifluoride. 

The reaction of xenon difluoride with a series of cis- and trans-phenyl substituted alkenes was examined in detail. 1,1-Diphenylethene, l,1-diphenyl-2-fluoroethene and 1.1-diphenyl-propene form vicinal 1,2-difluoro derivatives in 65 95% yield in dichloromethane solution with hydrogen fluoride as the catalyst.29-32 Two possible mechanisms were discussed.33... 

Diselenides can also be oxidatively fluonnated, as shown in equation 18 [775, 779]. Benzene selenyl fluoride is postulated as an intermediate during the fluo-roselenation of alkenes with diphenyl diselemde and xenon difluoride [73, 120]... 

Of course, most reactive metal fluorides, such as cobalt trifluoride [268] and vanadium pentafluoride, will react with alkenes but the reactions can be very difficult to control, except for haloalkenes [269]. Much easier control is possible with xenon fluorides [137], the reactivity decreasing in the series XeFe > Xep4 > Xep2. Since the first report of the use of xenon difluoride for the addition of fluorine to double bonds, many studies have been published and reviewed [54, 135] (Figure 3.61). 

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