Activity of amino-functionalised mesoporous solid bases in microwave-assisted condensation reactions

Aminopropylated functionalised hexagonal mesoporous silicas (HMS) and SBA-15 materials with different amino-loadings (5–30 wt.% NH2) were synthesized, characterised and their catalytic activities were subsequently investigated in the microwave-assisted Knoevenagel condensation of cyclohexanone and ethyl cyanoacetate as well as in the Michael reaction between 2-cyclohexen-1-one and nitromethane. The effects of the quantity of the catalyst in the reaction as well as a variety of microwave parameters including the power, temperature and time of microwave irradiation were optimised. High activities and selectivities to the condensation product could be achieved at short times of microwave irradiation for both base-catalysed processes. The low loaded HMS-5%NH2 and higher loaded SBA-15-20%NH2 were found to give the best activities in the reactions. This observation seems to be related to the significant deterioration observed in textural properties of HMS materials at amino-loadings larger than 10%.

► Synthesis of catalytically active aminopropyl functionalised silicas.
► Active materials in the Knoevenagel condensation under microwave irradiation
► Highly reusable materials under mild reaction conditions and short reaction times