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.

An efficient new procedure for the oxidation of cyclic ketones using macroporous silica supported hydrogensulfate ionic liquid as an active and low cost Brønsted acidic catalyst has been developed. The catalyst was easily separated from the reaction mixture and was recycled four times without any loss in activity.Figure optionsDownload as PowerPoint slide