Catalytic Asymmetric α‐Chlorination of 3‐Acyloxazolidin‐2‐one with a Trinary Catalytic System

Direct asymmetric α‐chlorination of aryl acetic acid derivatives was achieved with a novel trinary activation system consisting of a catalytic amount of NiCl 2 /( R )‐BINAP, Et 3 SiOTf, and a tertiary amine base. The reaction smoothly afforded the chlorinated compound in good yield with up to 89 % ee . Application of this reaction to a less acidic crotonic acid derivative gave the β,γ‐unsaturated α‐chlorinated compound through deprotonation at the γ‐position.