Journal
JOURNAL OF ORGANIC CHEMISTRY
Volume 76, Issue 2, Pages 588-600Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jo102124d
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Funding
- National Natural Science Foundation of China [20872041, 20572028]
- The Center of Analysis and Testing of Huazhong University of Science and Technology
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A small library of C-1-symmetric chiral diamines (L1-L9) was constructed via condensing exo-(-)-bornylamine or (+)-(1S,2S,5R)-menthylamine with various Cbz-protected amino acids. Among them, ligand Ll/CuCl2 center dot 2H(2)O 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 Ll/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.
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