Visible-Light-Enabled <i>Ortho</i>-Selective Aminopyridylation of Alkenes with <i>N</i>-Aminopyridinium Ylides

Abstract

By utilizing an underexplored reactivity mode of <i>N</i>-aminopyridinium ylides, we developed the visible-light-induced <i>ortho</i>-selective aminopyridylation of alkenes via radical-mediated 1,3-dipolar cycloaddition. The photocatalyzed single-electron oxidation of <i>N</i>-aminopyridinium ylides generates the corresponding radical cations that enable previously inaccessible 1,3-cycloaddition with a broader range of alkene substrates. The resulting cycloaddition adducts rapidly undergo subsequent homolytic cleavage of the N-N bond, conferring a substantial thermodynamic driving force to yield various β-aminoethylpyridines. Remarkably, amino and pyridyl groups can be installed into both activated and unactivated alkenes with modular control of <i>ortho</i>-selectivity and 1,2-<i>syn-</i>diastereoselectivity under metal-free and mild conditions. Combined experimental and computational studies are conducted to clarify the detailed reaction mechanism and the origins of site selectivity and diastereoselectivity.