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DOI: 10.1055/s-2008-1042694
Nd/Na-Catalyzed Anti-Selective Nitroaldol Reaction
Contributor(s):Mark Lautens, Praew ThansandotePublication History
Publication Date:
21 February 2008 (online)
Key words
neodymium - sodium - anti-selective nitroaldol reaction
Significance
A catalytic asymmetric anti-selective nitroaldol reaction has been developed using a Nd/Na/amide heterobimetallic catalyst. The yields, diastereoselectivities, and enantioselectivities are highest with aromatic aldehydes with an ortho-alkyl substituent. The products are useful anti-1,2-nitro alkanols, which can be rapidly converted into synthetically useful anti-1,2-amino alcohols.
Comment
Most asymmetric nitroaldol reactions are syn-selective, which makes this anti-selective methodology noteworthy. The key to the anti-diastereoselectivity is the heterobimetallic complex, which discourages chelation in a cyclic transition state and encourages the extended transition state (shown above) leading to the anti-product. Though the ee values for this reaction are moderate, the diastereoselectivities are usually high. For other anti-selective nitroaldol reactions, see: T. Risgaard, K. V. Gothelf, K. A. Jørgensen Org. Biomol. Chem. 2003, 1, 153; D. Uragachi, S. Sakaki, T. Ooi J. Am. Chem. Soc. 2007, 129, 12392.