The
controlled dispersion of polymeric sulfonic acids on suitable
heterogeneous supports paves the way to a new catalytic method for
the oxidation of a variety of benzylic methylenes to the corresponding
carbonyls by using hydrogen peroxide; narrowly dispersed silica nanoparticles
covered by fluorinated sulfonic acids ionomers allow selective oxidation
of toluene to benzaldehyde, minimizing undesired side reactions and
formation of wastes.
A cheap and easily recoverable heterogeneous catalyst could efficiently trigger C-P bond formation by selective addition of phosphites to the carbonyl group of aldehydes and ketones. The reactions afford the desired products in good to excellent yields and do not require the presence of a solvent.
The Friedel-Crafts acylation of anisole with acetic anhydride could be efficiently catalyzed by suitable silica-supported sulfonic acids. In particular, by using silica supported 4-ethylphenylsulfonic acid as catalyst it was possible to apply the synthetic procedure to different aliphatic anhydrides and aromatic compounds. It has been observed that the effect of the length of the alkyl chain of the anhydride is quite significant. Moreover, some attempts to regenerate the solid catalyst have been also discussed.
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