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Superacids, although first referred to as early as 1927, were only extensively studied in the last decade. Acidities up to 10(12) times that of sulfuric acid have now been obtained. The extremely low nucleophilicity of the counterions in superacidic systems is especially useful for the preparation of stable, electron-deficient cations, particularly carbocations. Many of these cations, which were formerly detectable only in the gas phase, can now be studied in solution. Novel organic syntheses that are not possible in ordinary acidic media can also be achieved in superacids, including syntheses of economically important hydrocarbons. The unique ability of superacids to bring about hydrocarbon transformations, even to activate methane to undergo electrophilic oligocondensation, can open up new fields in chemistry.

[reaction: see text] CuI-exchanged solids based on zeolite materials were investigated for the first time as catalysts in organic synthesis. The catalytic potential of these materials was evaluated in the Huisgen [3 + 2]-cycloaddition. Five CuI-exchanged zeolites were examined and CuI-USY proved to be a novel and efficient heterogeneous ligand-free catalyst for this "click chemistry"-type transformation.

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For the first time, copper(I)-exchanged zeolites were developed as catalysts in organic synthesis. These solid materials proved to be versatile and efficient heterogeneous, ligand-free catalytic systems for the Huisgen [3+2] cycloaddition. These cheap and easy-to-prepare catalysts exhibited a wide scope and compatibility with functional groups. They are very simple to use, easy to remove (by filtration), and are recyclable (up to three times without loss of activity). Investigations with deuterated alkynes and deuterated zeolites proved that this Cu(I)-zeolite-catalyzed "click" reaction exhibited a mechanism different from that reported for the Meldal-Sharpless version.

On the basis of our previous H/D exchange studies devoted to the quantification of the number of Brönsted acid sites in solid acids, we report here an innovative approach to determine both the amount and the localization of Mo atoms inside the Mo/ZSM-5 catalyst, commonly used for the methane dehydroaromatization reaction. The influence of Mo introduction in the MFI framework was studied by means of BET, X-ray diffraction, 27Al magic angle spinning NMR, NH3 temperature-programmed desorption, and H/D isotopic exchange techniques. A dependence was found between the decrease of acidic OH groups and the Mo content. Depending on the Si/Al ratio of the zeolite, i.e., the proximity of two Brönsted acid sites, the Mo atoms substitute a different number of OH groups. Consequently, a chemical structure was proposed to describe the geometry of the Mo complex in the channels of the ZSM-5 zeolite.

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The deuterium distribution observed in isobutane recovered after short contact times with the DF−SbF5 superacid at 0 °C shows that a very fast reversible protonation of all C−H bonds occurs before ionization of the alkane, in accord with the Olah σ-basicity concept. Comparison of the amounts of hydrogen with the amount of tert-butyl ions generated during ionization shows that the reaction is purely protolytic in HF containing up to 20 mol % SbF5, but becomes oxidative at higher concentrations.