Bio-assisted synthesized Ag(0) nanoparticles immobilized on SBA-15/cyclodextrin nanosponge adduct: Efficient heterogeneous catalyst for the ultrasonic-assisted synthesis of benzopyranopyrimidines

摘要

For the first time, SBA-15/cyclodextrin nanosponge adduct was synthesized through reaction of Cl-functionalized SBA-15 and amine-functionalized cyclodextrin nanosponge (CDNS). This adduct, which benefits from features of both SBA-15 and CDNS, was then used for immobilization of Ag(0) nanoparticles which were prepared and capped using a bio-based approach. Ag@CDNS-SBA-15 was applied as a heterogeneous catalyst for promoting the three-component reaction of benzaldehydes, 4-hydroxycoumarin and urea or thiourea under ultrasonic irradiation to furnish benzopyranopyrimidines. The reaction variables were optimized using response surface methodology. The catalytic activity of Ag@CDNS-SBA-15 was higher than those of Ag@CDNS, Ag@SBA-15 and Ag@SBA-15 + CDNS, confirming the contribution of both components to catalysis as well as a synergistic effect between CDNS and SBA-15. The role of CDNS was to accommodate the substrates and bring them to the vicinity of the Ag(0) nanoparticles. Notably the catalyst was reusable and could be recovered and reused for up to four reaction runs with slight Ag(0) leaching and loss of catalytic activity.