SET-induced biaryl cross-coupling: an S(RN)1 reaction.

The SET-induced biaryl cross-coupling reaction is established as the first example of a Grignard S(RN)1 reaction. The reaction is examined within the mechanistic framework of dissociative electron transfer in the presence of a Lewis acid. DFT calculations show that the reaction proceeds through a radical intermediate in the form of an Mg ion-radical cage, which eludes detection in trapping experiments by reacting quickly to form an MgPh2 radical anion intermediate. A new mechanism is proposed.