Catalytic Electrophilic CH Silylation of Pyridines Enabled by Temporary Dearomatization

A C? H silylation of pyridines that seemingly proceeds through electrophilic aromatic substitution (S_EAr) is reported. Reactions of 2‐ and 3‐substituted pyridines with hydrosilanes in the presence of a catalyst that splits the Si? H bond into a hydride and a silicon electrophile yield the corresponding 5‐silylated pyridines. This formal silylation of an aromatic C? H bond is the result of a three‐step sequence, consisting of a pyridine hydrosilylation, a dehydrogenative C? H silylation of the intermediate enamine, and a 1,4‐dihydropyridine retro‐hydrosilylation. The key intermediates were detected by ¹H NMR spectroscopy and prepared through the individual steps. This complex interplay of electrophilic silylation, hydride transfer, and proton abstraction is promoted by a single catalyst.