Simply air: Vanadium-catalyzed oxidative kinetic resolution of methyl o-chloromandelate by ambient air

Vanadium-catalyzed oxidative kinetic resolution (OKR) of methyl o-chloromandelate 2a, key intermediate of the well-known oral antiplatelet agent (S)-clopidogrel, was achieved by ambient air for the first time. The air oxidation system, which was composed of vanadium and tridentate Schiff base ligands derived from amino alcohols and salicylaldehyde derivatives, afforded an efficient and economic approach to the target intermediate with high enantioselectivities (>99% ee).