Sulfoxidation inside a C₃-vanadium(V) bowl-shaped catalyst

The confined enantiopure oxido-vanadium complex SSS-RRR-1 was synthesized and tested as a catalyst for the oxidation of sulfides into sulfoxides. This catalyst is very efficient with a reaction rate more than 300 times higher than that of the model compound SSS-RRR-3, and a turnover number (TON) close to 10⁵ was reached in combination with a good selectivity (more than 90%) in the sulfoxide product. Moreover, enantiomerically enriched sulfoxide can be obtained, breaking through the major limitation of the previous chiral vanatrane catalysts that show no detectable enantiomeric excess (ee). Further investigations revealed that the complex SSS-RRR-1 adopts a bowl-shaped structure with an open hydrophobic pocket. The microenvironment of the chiral pocket above the metal center accounts for the strong improvement in catalytic activity and enantioselectivity.