Asymmetric vanadium- and iron-catalyzed oxidations: new mild (R)-modafinil synthesis and formation of epoxides using aqueous H2O2 as a terminal oxidant

The enantioselective oxidation of thioanisole to methyl phenyl sulfoxide and the epoxidation of several alkenes, including terminal ones, have been realized by using new iron(III) complexes, generated in situ from primary amine-derived non-symmetrical Schiff base ligands and aqueous H2O2 as environmentally benign oxidant. Further investigations on vanadium catalysis and the application of both catalytic systems in the synthesis of enantiomerically-enriched chiral drug (R)-modafinil were undertaken. It was found that the vanadium-based catalytic system (VO(acac)2/ligand 6), is able to provide (R)-modafinil in quantitative yield and acceptable enantiomeric excess within a very short reaction time (15 min).