Rhodium-Catalyzed Addition of (Trialkylsilyl)arenes to Electrophiles via π-Coordination-Driven C-Si Bond Activation.

Abstract

Aromatic organosilicon compounds serve as valuable synthons due to their diverse reactivities, excellent compatibility with various functional groups, and ready availability. However, (trialkylsilyl)arenes, despite their potential utility, are generally considered unsuitable substrates for transition-metal-catalyzed cross-coupling due to the low polarity of their covalent C(aryl)-Si bonds and the significant steric hindrance imposed by alkyl substituents. These factors render them inert toward reactions with transition metals, such as transmetalation and oxidative addition. In this study, we present a method for the rhodium-catalyzed addition of (trialkylsilyl)arenes to electrophiles via π-coordination-driven desilylation. We propose that a dicationic rhodium species activates the unbiased C(aryl)-Si bond, increasing its polarity by forming an η6-arene complex, thereby facilitating heterolysis. The resulting phenyl anion complex readily engages in addition reactions with external electrophiles, effectively forming C-C bonds. Through comprehensive computational studies, we have unraveled an unexpected stepwise pathway for desilylation with fluoride. This pathway involves the addition of fluoride to the aromatic ring, followed by a 1,2-migration of fluoride, ultimately culminating in the departure of fluorotrimethylsilane.