Ionic-liquid supported oxidation reactions in a silicon-based microreactor

The combination of microfabrication and reaction engineering techniques has the potential to produce powerful microreactors. In a microreactor, aqueous buffers provide high electroosmatic mobility and no external pumping is required. While numerous reactions have been demonstrated to be highly efficient in microreactors, so far there has been no report on the epoxidation of cyclohexene in a microreactor. This is mainly due to the reduced solubility of cyclohexene in aqueous media. The greater volatility of cyclohexene leading to long reaction times is another reason. To improve the solubility of cyclohexene in the reaction buffer, a water soluble ionic-liquid 1-butyl-3-methylimidazolium tetrafluoroborate was used, also for the first time in microreactor work. In this letter, four different catalysts (i.e., manganese(II) and copper(II) complexes of Schiff and reduced Schiff bases) were synthesized and used for the oxidation reactions considered. The reactions were monitored by gas chromatography/mass spectrometry. The microreactor performance was evaluated by comparing with a conventional (batch scale) reaction. Catalytic activities and yields were found to be relatively high for the copper(II) complexes as compared with the conventional route.