New chiral Schiff bases derived from (+)- and (-)-alpha-pinenes in the metal complex catalyzed asymmetric oxidation of sulfides

New chiral Schiff bases were derived from (+)- and (-)-alpha-pinenes for the first time. Coordinated to vanadium ions, they can be used as ligands in catalytic oxidation of sulfides into chiral sulfoxides. Conditions for the asymmetric oxidation of thioanisole to methyl phenyl sulfoxide in optical purity up to 32% were found. Variation of substituents in the ligand has a significant effect not only on enantioselectivity of the reaction, but also on absolute configuration of the sulfoxide formed.