Baeyer-Villiger Oxidation of Cyclic Ketones by Using Tin-Silica Pillared Catalysts.

The Baeyer-Villiger oxidation is an important transformation of ketones into esters and particularly for cyclic ketones to lactones. We report here preparation and catalytic activity of layered Sn-silicate catalysts and mesoporous ordered silica catalysts in this reaction. Sn was introduced by using so-called tin-silica pillaring or by impregnation with a mixture of tetraethylorthosilicate and tin(IV) alkoxide. The prepared catalysts were characterized by XRD, N2 physisorption, SEM, UV/Vis, and inductively coupled plasma optical emission spectroscopy (ICP-OES) techniques and the catalysts were studied in the Baeyer-Villiger oxidation of cyclopentanone, norcamphor, and 2-adamantanone with aqueous hydrogen peroxide. Norcamphor and 2-adamantanone were oxidized easily with selectivity up to 99 %. Sn-MS and IPC-1-SnPI materials exhibited the highest conversions (e.g., norcamphor: Sn-MS 37 %, IPC-1-SnPI 36 % after 8 h vs. Sn-MCM-41 22 %). On the other hand, oxidation of cyclopentanone suffered from product hydrolysis to the corresponding 4-hydroxybutanoic acid. [ABSTRACT FROM AUTHOR]