Synthesis of novel chiral oxazoline-Schiff base ligands for the catalytic asymmetric chlorination of β-keto esters

A series of novel monooxazoline-Schiff base ligands 1 has been successfully synthesized. The Cu(I)–1a complex showed excellent catalytic activities with up to 83% ee for the asymmetric α-chlorination of β-keto esters.

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2-((E)-((S)-2-methyl-1-((S)-4-phenyl-4,5-dihydrooxazol-2-yl)propylimino)methyl)phenolC20H22N2O2Ee = 100%[α]D20=-34.8 (c 0.90, CHCl3)Source of chirality: chiral poolAbsolute configuration: (1S,2S)

1-{[2-Methyl-1-(4-phenyl-4,5-dihydrooxazol-2-yl)propylimino]methyl}naphthalen-2-olC24H24N2O2Ee = 100%[α]D20=-26.4 (c 1.65, CHCl3)Source of chirality: chiral poolAbsolute configuration: (1S,2S)