Enantioselective chlorination of β-keto esters and amides catalyzed by chiral copper(II) complexes of squaramide-linked bisoxazoline ligand

Enantioselective chlorination of β-keto esters and amides catalyzed by squaramide-linked bisoxazoline ligand–Cu(OAc)2 complexes was investigated. The corresponding chlorinated products were obtained in excellent yields with moderate enantioselectivities. The effect of solvent, temperature, Lewis acid, and ligand structure on the reaction is discussed. This was the first investigation of catalytic asymmetric α-chlorination of β-keto amides. This study has highlighted that a simple chiral squaramide–oxazoline with cheap Cu(OAc)2·H2O complexes can catalyze this chlorination.

Graphical abstractEnantioselective chlorination of β-keto esters and amides catalyzed by squaramide-linked bisoxazoline ligand–Cu(OAc)2 complexes were investigated. The corresponding chlorinated products were obtained in excellent yields with moderate enantioselectivities. The effects of solvent, temperature, Lewis acid, and ligand structure on the reaction are discussed.Figure optionsDownload full-size imageDownload as PowerPoint slide