Supported hydrogensulfate ionic liquid catalysis in Baeyer-Villiger reaction

We report here the method of synthesis and characterisation of ionic liquid: 1-methyl-3-(triethoxysilylpropyl)imidazolium hydrogensulfate, anchored onto solid support via cation-anion stays unbounded to the surface. As a support, we used a silica material with the extensive system of meso- and macropores. The structure of the support was not destroyed after the immobilisation of the ionic liquid. The new material was tested as acidic catalyst with the Baeyer-Villiger reaction. Cyclic ketones were readily oxidised with 68% hydrogen peroxide in dry dichloromethane to their corresponding lactones in high yields (60-91%) at 50 °C within a short time (5-20 h). The use of hydrogen peroxide and a heterogeneous catalyst allows a clean oxidation and the possibility of easy catalyst removal by simple filtration and reuse three times in another oxidation process without lost of catalyst activity.