Chiral VIVO-Sal-Indanol complex over modified SBA-15: An efficient, reusable enantioselective catalyst for asymmetric sulfoxidation reaction

Abstract

A reusable, mesoporous, heterogeneous vanadium complex, VIVO-Sal-Ind-SBA-15 has been synthesized first time from (1R,2S)-(+)-Cis-1-amino-2-indanol for enantioselective sulfoxidation reaction. The physico-chemical properties of the functionalized catalyst were analyzed by a series of characterization techniques like XRD, N2 sorption measurement isotherm, TEM, FT-IR, XPS, EPR, DRS UV–Visible, ICP-OES and solid & liquid state 13C, 29Si and 51V NMR spectroscopy. Powder X-ray diffraction patterns, TEM and N2 physisorption analysis confirmed the retention of mesoporous structure after various modifications. Solid-state NMR (13C CP-MAS NMR, 29Si MAS NMR) and FT-IR analysis certified the integrity of organocatalyst residing inside the pore channels of the mesoporous support. Further, XPS, EPR, 51V NMR and DRS UV–Visible analyses help to find out the oxidation state and coordination environment of vanadium in VIVO-Sal-Ind-SBA-15. Catalytic evaluation in asymmetric sulfoxidation reaction of sulfides indicated that VOIV-Sal-Ind-SBA-15 exhibited higher catalytic activity, stability, reusability and comparable enantioselectivity than SBA-15, PrNH2-SBA-15, neat VIVO-Sal-Indanol complex and without catalyst. The effect of different catalysts, temperature, solvents and substrates on sulfoxidation reaction were examined in order to optimize the conversion and enantioselectivity of thioanisoles to sulfoxides.