Hydrogen fluoride catalysis

Xenon difluoride [4, 5, 7, 8,10] is a white crystalline material obtained through the combination of fluorine and xenon m the presence of light The reagent is commercially available and possesses a relatively long shelf-life when stored cold (freezer) Xenon difluoride is very effective for small-scale fluormation of alkenes and activated nucleophilic substrates. The reactions are usually conducted between 0 °C and room temperature in chloroform or methylene chloride solutions Hydrogen fluoride catalysis is sometimes helpful Xenon difluoride reacts in a manner that usually involves some complexation between the substrate and reagent followed by the formation of radical and radical cation intermediates... 

Hydrogen Fluoride Catalysis J. H. Simons Entropy of Adsorption Charles Kemball... 

Until recently, halogen substituted alkanes were thought to be inert to xenon difluoride, but detailed examination has shown that common solvents such as dichloromethane (3) and chloroform (4) undergo fluorine-chlorine and fluorine-hydrogen exchange at room temperature due to hydrogen fluoride catalysis.15... 

Cycloalkenes treated with xenon difluoride in dichloromethane form vicinal difluorides in high yield with hydrogen fluoride catalysis. Indene produces difluorides in 72% yield the preferred <7 t/-isomer is formed.36... 

Aromatic molecules with hydroxy, amino and alkoxy groups underwent ringfluorination by xenon difluoridc in the absence of hydrogen fluoride catalysis, functional groups being unaffected.63... 

In the absence of hydrogen fluoride catalysis, anisole. phenol, 2-naphthol, 1,2-dimethoxybenzene, 1,2-dihydroxybenzene and 1,3-dihydroxybcnzene react with xenon difluoride to give monosubstituted products in fair to good yield (Table 15). ... 

---