Chiral vanadyl salen catalyst immobilized on mesoporous silica as support for asymmetric oxidation of sulfides to sulfoxides

Abstract

cThe chiral vanadyl salen complex was immobilized into mesoporous silica by a covalent grafting method using 3-aminopropyltriethoxysilane as a reactive surface modifier. The formation and integrity of the complex have been confirmed by FT-IR, UV-vis and BET measurements and the complex was tested in the asymmetric oxidation of sulfide to sulfoxide using H 2 O 2 as oxidant. The immobilized complex showed better catalytic activity than the neat complex, while the neat complex has deactivated in the reaction. The combination of the heterogenized catalyst, H 2 O 2 and CH 2 Cl 2 as solvent offers a selective catalytic system for oxidation of sulfide to sulfoxide with a low but significant enantioselectivity in the range of 8-10% ee. In addition, the heterogenized catalyst could be easily separated from the products and reused.

Fe3O4@S‐ABENZ@VO: Magnetically separable nanocatalyst for the efficient, selective and mild oxidation of sulfides and oxidative coupling of thiols

“…The C‐N stretching frequency is present in the region 1350–1410 cm −1 in the spectra of Fe 3 O 4 @S‐ABENZ and fe3o4@s‐abenz@VO. A characteristic band due to the C═C stretching frequency appears as a strong band at 1600 cm −1 in Fe 3 O 4 @S‐ABENZ and fe3o4@s‐abenz@VO spectra . The characteristic V═O stretching frequency in the Fe 3 O 4 @S‐ABENZ@VO spectrum appears at 995 cm −1 , within the range of 970–997 cm −1 reported for similar oxovanadium(IV) complexes …”

X-ray and DFT-calculated structures of a vanadyl Schiff base complex: (methanol-κO)[2-methoxy-6-({2-[(2-oxido-3-methoxybenzylidene)amino]benzyl}iminomethyl)phenolato-κ4O1,N,N,O1′]oxidovanadium(IV) monohydrate

“…Oxovanadium(IV) complexes of Schiff bases are now established as an important class of drugs because of their medical importance due to their insulin-like effect (Thompson et al, 1999). Additionally, these complexes are used in some chemical processes as catalysts (Ben Zid et al, 2010), and also as biological models in understanding the structure of biomolecular and biological processes (Meshkini & Yazdanparast, 2010). Furthermore, vanadium compounds are interesting because of their adverse effect on the hydroprocessing catalysts used in refining crude oil (Bu et al, 1996).…”

A vanadyl Schiff base complex: {2,2′-[1,1′-(o-phenylenedinitrilo)bis(ethan-1-yl-1-ylidene)]diphenolato}oxovanadium(IV)

“…There is an extensive literature on their application in some important industrial and life processes (Chang et al, 1997;Mohammadi & Yazdanparast, 2009;Boghaei et al, 2006). They are interesting because of their antitumour and antiviral properties (Meshkini & Yazdanparast, 2010;Rehder, 2003); it was also demonstrated that they can show antioxidant activity (Mohammadi & Yazdanparast, 2010) and be applied as catalysts (Ben Zid et al, 2010). The oxide group of oxovanadium complexes has taken part in a number of oxide-transfer reactions (Adã o et al, 2009).…”