| Research Abstract |
The catalytic applications of Nafion-H, a superacidic perfluororesinsulfonic acid in organic synthesis are investigated. Nafion-H, the acid form of a commercial Nafion-K ionomer, is a highly acidic (Ho ≧-12) solid catalyst superior to conventional resinsulfonic acids such as sulfonated polystylenes 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, and polymerizations and so on. Nafion-H and related perfluoroalkanesulfonic acids are not only much stronger acids but sre also stable in corrosive enviroments and at temperature up to 210℃. Furthermore specific advantage of using insoluble resins as catalysts have been provided 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
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groups by simulating high dilution conditions ; iii) the possibility of reusing recovered reagents as well as eliminating the use of volatile or noxious substances. The presently developed procedure provides an excellent yield, easy isolation of the products, and ready regeneration of the catalyst without any loss of activity. Furthermore, the workup of the reaction mixture is extremely simple, involving filtration of the solid catalyst (which can be reused after simple regeneration). Only a catalytic amount of catalyst was needed instead of the usual stoichiometric quantity required for the conventional Lewis acid catalysts that bind to the hydroxyl droup or NH group. Specific advantages of using insoluble resins as catalysts include the prevention of intermolecular reactions of reactive species or functional groups by simulating high dilution conditions.
1. Super-acidic perfluorinated resinsulfonic acid (Nafion-H) catalysis in organic synthesis Nafion-H has been shown to be useful and versatile acid catalyst for organic reactions. It is effective in a wide range of liquid and gas phase reactions, including dehydration of alcohols, rearrangements, electrophilic substitutions on aromatic nuclei, and polymerizations. Especially, the presently developed procedure provides a range of application for the synthesis of macrocycles by Nafion-h catalyzed cyclibenzylation.
2. Development of functionalized Nafion derivatives We have developed an efficient and convenient procedure for oxidation of polycondensed aromatic hydrocarbons to quinones with Ce (IV) or Cr (III) impregnated Nafion-K catalyst using various co-oxidants, which are enable to proceed quite readily, giving good to moderate yields. The use of functionalized Nafion derivatives can be achieved various type of organic transformation. Less
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