ORGN 135 |
| In the past few years organocatalysis has emerged as a powerful approach for the preparation of important optically active building blocks. The LUMO-lowering activation of α,β-unsaturated aldehydes using the reversible formation of iminium ions with chiral imidazolidinones was reported as a valuable platform for the development of enantioselective organocatalytic Diels-Alder reactions as well as [3 + 2] cycloadditions. Herein we describe the use of chiral amine organic acid salt 1 as a highly efficient catalyst for the 1,3-dipolar cycloadditon of nitrones and α,β-unsaturated aldehydes to provide isoxazolidines (Scheme) - useful synthons for the construction of biologically important architectures – in high yields and excellent enantioselectivities. Organocatalyst 1 is prepared in one step from commercially available starting materials. The free base of 1 has been used in previous organocatalytic studies, but to the best of our knowledge this is the first account for the organocatalytic properties of 1.
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Asymmetric Reactions and Syntheses, Metal-Mediated Reactions, Combinatorial, Parallel, and Solid-Phase Chemistry
8:00 PM-10:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Division of Organic Chemistry |
