Design of Leaving Groups in Radical CC Fragmentations: Through‐Bond 2c–3e Interactions in Self‐Terminating Radical Cascades |
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Authors: | Dr Sayantan Mondal Brian Gold Rana K Mohamed ProfDr Igor V Alabugin |
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Institution: | Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306‐4390 (USA) |
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Abstract: | Radical cascades terminated by β‐scission of exocyclic C?C bonds allow for the formation of aromatic products. Whereas β‐scission is common for weaker bonds, achieving this reactivity for carbon–carbon bonds requires careful design of radical leaving groups. It has now been found that the energetic penalty for breaking a strong σ‐bond can be compensated by the gain of aromaticity in the product and by the stabilizing two‐center, three‐electron “half‐bond” present in the radical fragment. Furthermore, through‐bond communication of a radical and a lone pair accelerates the fragmentation by selectively stabilizing the transition state. The stereoelectronic design of radical leaving groups leads to a new, convenient route to Sn‐functionalized aromatics. |
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Keywords: | alkynes cyclization domino reactions radical reactions through‐bond interactions |
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