Flash Communication: Siloxides Promote the Iron-Catalyzed Borylation of Aryl Chlorides

In contrast to alkoxide salts, siloxide salts MOSiR₃ (M = Na, Li) can be used to good effect as activators for B₂pin₂ in the iron-catalyzed borylation of aryl chloride substrates, in many cases giving results comparable to or better than those obtained previously with highly pyrophoric <i>^t</i>BuLi acting as an activator. Preliminary mechanistic investigations reveal a protracted induction period, most likely associated with precatalyst reduction, and these also suggest that the NaOSi<i>^t</i>BuMe-activated B₂pin₂ is not as reducing as the equivalent <i>^t</i>BuLi-activated species.