B(C ₆ F ₅ ) ₃ -Catalyzed Intramolecular Thio- and Selenoamination of Aminoalkenes

A metal-free borane-catalyzed chalcogenative cyclization strategy for constructing chalcogen-containing heterocycles from unactivated alkenes with thiosuccinimides or selenophthalimide is developed herein. This method results in excellent substrate and functional group tolerance and high levels of chemo- and regioselectivity. Furthermore, the protocol enables the late-stage diversification of commercially available pharmaceuticals. Mechanistic studies suggest that the borane catalyst activates thiosuccinimides and selenophthalimides to form electrophilic species, which subsequently induce this chalcogenative annulation.