Selective Carbocation Functionalization by Catalytic Transchalcogenation Reactions

Introducing functionalities via acid-mediated carbocation chemistry is conceptually straightforward, but typically lacks in selectivity and broad-scale applicability, which is further hampered by the need for toxic reaction partners. Here, we show that small S- and Se-based functionalities can be selectively and safely introduced into feedstock molecules via acid-catalyzed transchalcogenation reactions. A designable y-keto donor compound delivers the functionality through the formation of a trialkyl chalcogenonium intermediate that is prone to elimination in conjunction with the acid catalyst and its counteranion. We demonstrate how this strategy enables chemo-, regio-, and stereoselective construction of C(sp³)─S and ─Se bonds, offering clear advantages over classical acid-catalyzed carbocation functionalization.