METAL-FREE SELECTIVE SP3 C-H IMINATION AND COVALENT POSTSYNTHETIC MODIFICATION OF POLYSTYRENE BY DIRECT C-H AMINATION
Over the past two decades, there has been a high demand for methods enabling direct alkane C–H amination. Alkylamines are commonly found as natural products and bioactive compounds, and amino functionalization can improve the properties of commodity polymers. Transition-metal-catalyzed C–H amination has emerged as a powerful tool for C–N bond formation, but these reactions typically rely on nitrogen protecting groups such as sulfonamides, which limits substrate scope and requires multiple steps. My work focused on developing a metal-free C-H amination method, which offers new and useful amination scope and selectivity and avoids toxic or colored metal residues. Specifically, we developed a mild and selective protocol for preparing primary and secondary aliphatic amines in a single pot, based on intermolecular sp3 C-H imination. Our approach involves a unique hydrogen-atom transfer/radical addition mechanism, which differs from the more established Hoffman-Löffler-Freytag amination. From there, we have successfully transferred this method from small molecules to macromolecules, as the amino functional group is attractive for polymer modification. We developed a mild and selective simple amination of polystyrene without chain cleavage and cross linking by radical sp3 C-H imination, using a protocol we reported for the sp3 C-H imination of small molecules. This process incorporates primary amines, primary ammonium salts, and benzophenone ketimines in a straightforward manner, which will further inform future development of materials by the direct modification of polymer.
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