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Development of Bifunctional Aza-Bis(oxazoline) Copper Catalysts for Enantioselective Henry Reaction

2010; American Chemical Society; Volume: 75; Issue: 19 Linguagem: Inglês

10.1021/jo1009867

1520-6904

Kai Lang, Jongwoo Park, Sukwon Hong,

Coordination Chemistry and Organometallics

Base-functionalized aza-bis(oxazoline) ligands were prepared to explore the concept of dual activation through the Lewis acid and a tethered tertiary amine base. The catalytic activity of the Cu complex was evaluated for the asymmetric Henry reaction. Compared with a corresponding unfunctionalized copper complex with external 1-benzyl-4-ethylpiperazine base, the ethylpiperazine-functionalized aza-bis(oxazoline) copper catalyst resulted in rate acceleration (2.5 times) as well as improved enantioselectivity (72% ee vs 92% ee).