The catalytic applications of Nafion-H, a superacidic perfluororesinsulfonic acid in organic synthesis are reviewed. Nafion-H, the acid form of a commercial Nafion-K ionomer, is a highly acidic (H0≥-12) solid catalyst superior to conventional resinsulfonic acids such as sulfonated polystyrenes in its catalytic activity, thermal stability and chemical resistance.
Nafion-H catalyst is effective in a wide range of liquid and gas phase reactions, including electrophilic substitutions on aromatic nuclei, dehydration of alcohols, rearrangements, polymerizations and so on. Nafion-H and related perfluoroalkanesulfonic acids are not only much stronger acids but are also stable in corrosive environments and at temperature up to 210°C. Furthermore, specific advantages of using insoluble resins as catalysts include i) ease of by-product separation from the main reaction product usually by simple filtration; ii) prevention of intermolecular reaction of reactive species or functional groups by simulating high dilution conditions; iii) the possibility of reusing recovered reagents as well as eliminating the use of volatile or noxious substances.