Iodine fluoride reaction with alkenes

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 %). 

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... 

The g.l.c. separation of cis- and /m/w-epoxy-esters forms the basis of a new procedure for determining the proportion of cis- and tra/w-isomers in a mixture. The report that w-chloroperbenzoic acid can be used at 90 without decomposition in the presence of suitable radical inhibitors may be of value when epoxidizing alkenes of reduced reactivity. Several fluorostearic acids have been prepared by interaction of mesyloxy-acids with tetrabutyl-ammonium fluoride in acetonitrile. A procedure for methylation (by diazomethane in the presence of boron trifluoride) and demethylation (by reaction with sodium borohydride and iodine, followed by methanol), with retention of optical activity, could prove useful in the synthesis of compounds of known configuration. ... 

Alkyl bromides and iodides are converted into the corresponding fluorides in good yield with mercury(I) fluoride.31 36 Fluorinations of polyhalides are complicated by elimination reactions which give a mixture of alkenes and fluorination products. The fluorinating ability ofmercury(l) fluoride can be increased by the addition of bromine or iodine which results in the formation of mercury(II) fluorohalide.37 38 An example of the reaction of mercury(I) fluoride with simple perfluoroalkyl iodides is the formation of 2//.2//-octafluorobutane (12).39... 

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