An efficient heterogeneous Cu-grafted mesoporous organosilicas nanocatalyst for two and three component C-S coupling reactions.

ABSTRACT

Furfural-imine functionalized mesoporous organosilica material has been synthesized by post-synthesis surface functionalization of 2D-hexagnoal mesoporous SBA-15 with organosilane precursor 3-aminopropyltriethoxy-silane (APTES) followed by Schiff-base condensation with furfural. On the other hand, furfural-imine functionalized MCM-41 has been synthesized by Schiff-base condensation of furfural and 3-aminopropyltriethoxy-silane (APTES) followed by its hydrothermal co-condensation with tetraethylorthosilicate (TEOS) in the presence of a cationic surfactant CTAB. Subsequent reaction of the imine-functionalized mesoporous organosilicas with Cu(OAc)2 in absolute ethanol produced Cu(II)-grafted mesoporous nanocatalysts 1 and 2, respectively. Powder XRD, HR TEM, FE SEM, N2 sorption and EPR experimental tolls are employed to characterize these Cu-grafted furfural-imine functionalized nanocatalysts. Cu-grafted MCM-41 (1) showed very good catalytic efficiency for the coupling of aryl bromides and thiophenol under aerobic conditions to produce different thioethers. On the other hand, Cu-anchored mesoporous SBA-15 nanocatalyst (2) exhibited high catalytic activity for one-pot three component coupling of different aryl halides with thiourea and benzyl bromide in aqueous medium to produce different aryl alkyl thioethers in very good yields. Both Cu-grafted mesoporous nanocatalysts can be efficiently reused for several reaction cycles.