Synthesis of C1-Symmetric Chiral Secondary Diamines and Their Applications in the Asymmetric Copper(II)-Catalyzed Henry (Nitroaldol) Reactions

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• 作者：Yirong Zhou ; Junfang Dong ; Fanglin Zhang ; Yuefa Gong
• 刊名：Journal of Organic Chemistry
• 出版年：2011
• 出版时间：January 21, 2011
• 年：2011
• 卷：76
• 期：2
• 页码：588-600
• 全文大小：1045K
• 年卷期：v.76,no.2(January 21, 2011)
• ISSN：1520-6904

文摘

A small library of C₁-symmetric chiral diamines (L1鈭?b>L9) was constructed via condensing exo-(鈭?-bornylamine or (+)-(1S,2S,5R)-menthylamine with various Cbz-protected amino acids. Among them, ligand L1/CuCl₂路2H₂O complex (2.5 mol %) shows outstanding catalytic efficiency for Henry reaction between a variety of aldehydes and nitroalkanes to afford the expected products in high yields (up to 98%) with excellent enantioselectivities (up to 99%) and moderate to good diastereoselectivities (up to 90:10). This process is air- and moisture tolerant and has been applied to the synthesis of (S)-2-amino-1-(3,4-dimethoxyphenyl)ethanol (9), a key intermediate for (S)-epinephrine and (S)-norepinephrine. On the basis of HRMS and X-ray diffraction analysis of the L1/CuCl₂ complex, a transition-state model was proposed to explain the origin of asymmetric induction. The low catalyst loading, excellent yields and enantioselectivities, inexpensive copper salt, and mild reaction conditions make our catalytic system to be practically useful.