Highly stable Lewis acidic trifloaluminate ionic liquid supported on silica and metallosilicates as an efficient catalyst for continuous flow aminolysis of epoxides

In this work heterogeneous catalysts based on hybrid materials consisted of calcium and/or magnesium silicates and modern task-specific ionic liquids (supported ionic liquid phase material) dedicated particularly for continuous flow synthesis of fine chemicals with liquid reagents were designed. Pure SiO2 (as a reference sample), as well as magnesium (MgO-SiO2) or calcium (CaO-SiO2) silicates were used as supports for Lewis acidic trifloaluminate ionic liquids immobilized via chemical bound. The lowest ionic liquid loading was determined for SiO2 (15.58 wt%) and the highest for CaO-SiO2 (23.70 wt%). Resulted catalysts were used for the optimization of process parameters of the synthesis of β-amino alcohols in batch reactor (molar ratio aniline: styrene oxide 1.1:1; 1 mol% of catalyst, 60 °C). Not only the most active (conversion of styrene oxide 100.0% and selectivity to main product 98.7%) but also stable in 3 cycles of the process was the catalyst based on MgO-SiO2. The activity of poorly recyclable precursor of ionic liquid used as an active phase Al(OTf)3 was also lower (conversion 87.3% and selectivity 94.6%). Substrate scope confirmed the versatility of this method. The key achievement of the research was the confirmation of activity and stability of the most active catalyst in batch process for the aminolysis of epoxide in the presence of heterogeneous catalyst based on MgO-SiO2 in flow system through 72 h (conversion 81.1%, selectivity 95.9%). The proof of concept for the design of this catalytic system for production of selected fine chemicals is shown in this study.