Catalytic behavior of copper-amine complex supported on mesoporous silica SBA-15 toward mono-Aza-Michael addition: role of amine groups

This work concerns the preparation and modification of mesoporous silica SBA-15 with different amine-copper complexes in order to study their impact on the catalytic behavior via Aza Michael addition. Firstly, SBA-15 was prepared hydrothermally, then functionalized by mono-, di- and tri-amine, and in the second step, copper (II) was anchored. The catalytic activity of these solids was evaluated at room temperature under liquid-phase conditions. Effects of catalyst nature, catalyst mass, reaction time and the starting reagents nature were investigated. Cu@SBA-15 (non-aminated) was shown to be efficient in the Aza Michael addition, but after its second re-use, a progressive decrease in the product yield was obtained due to copper leaching. The catalytic behavior of all prepared catalysts showed a selective reaction via the mono-Aza-Michael addition. Amongst all the catalysts, the one containing the monoamine-copper complex led to the highest yield. This catalyst was used in four consecutive cycles without significant loss of activity, which confirms its stability.