Intermolecular Reactions of γ‐Halocarbanions – Stepwise Analogs of 1,3‐Dipolar Cycloaddition |
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Authors: | Micha? Barbasiewicz Mieczys?aw M?kosza |
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Institution: | 1. Faculty of Chemistry, University of Warsaw, Pasteura 1, PL‐02‐093 Warsaw;2. Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, PL‐01‐224 Warsaw |
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Abstract: | γ‐Halocarbanions, short‐lived intermediates, add to electron‐deficient double bonds of aldehydes, Michael acceptors, and imines to form anionic adducts that enter intramolecular 1,5‐substitution to form five‐membered rings of tetrahydrofurans, cyclopentanes, and pyrrolidines, respectively. Although the γ‐halocarbanions can be generated by simple deprotonation of appropriate precursors, a wealth of other methods based on Lewis acid‐catalyzed opening of cyclopropanes with formation of dipolar species utilizes a similar mechanistic scheme. In our review, we analyze kinetic relations of elementary processes in the multistep transformations, and demonstrate how structural factors influence the mechanisms and selectivity of the reaction. |
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Keywords: | γ ‐Halocarbanions Cycloadditions Carbanions |
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