γ-C(sp2)–H Arylation of Allylamines Using PdII and CO2 as a Transient Directing Group

Although C–H activation has become a powerful tool in the synthesis of complex molecules from simple precursors, transition metal-catalyzed reactions involving free alkenes often lead to insertion-type reactions. Herein we demonstrate that the addition of carbon dioxide in the form of dry ice allows the C(sp2)–H arylation of both secondary and primary allylamines in the presence of a PdII catalyst. Notably, the product 3,3’-diarylallylamine motif is prevalent in a variety of biologically-relevant structures, and this method represents the most straightforward synthesis of these targets to date. Key features of the method are the ability to access relatively mild conditions that facilitate a broad substrate scope, as well as direct diarylation of terminal allylamine substrates. In addition, several complex and therapeutically-relevant molecules are included to demonstrate the utility of the transformation.