Chemoselective Hydroheteroarylation of Alkenes via Photoredox-Neutral Proton- and BF 3 -Mediated Electron Transfer.

Herein, we have developed a complementary entry to enable hydroheteroarylation of alkenes involving basically photoredox dearomatizative heterocyclic carbon radical formation through acid-coupled electron transfer followed by Giese addition. While protonic solvent and thiophenol additive enabled two molecular hydroheteroarylations of alkenes, the nonproton environment with BF ₃ altered the chemoselectivity over cascade hydroheteroarylation of alkenes by radical addition of heteroaromatics with two molecular alkenes. This chemoselectivity can be mechanistically attributed to the dynamically favored hydrogen atom transfer via the cyclic transition state.