Site-Selective Electrochemical C–H Silylations of Pyridines Enabled by Temporary Reductive Dearomatization

Site-selective pyridine C–H silylation chemistry is of significant value but remains underdeveloped. In this study, we demonstrated that electron-deficient pyridines are highly selectively reductively silylated at the C4-position under electrochemical reduction conditions. A diverse array of C4-silylated pyridines was synthesized in good-to-excellent yields using common chlorosilanes as activating agents. Additionally, the use of bulky chlorotriisopropylsilane led to the formation of the C5-silylated products, albeit in moderate yields. This method is noteworthy due to its mild reaction conditions, simplicity, and excellent site selectivity for a diverse range of pyridines. Mechanistic studies revealed that the reaction involves temporary dearomatization to yield a 1,4-disilylated compound, which is quickly converted into the final C4-silylated pyridine through hydrolysis and air-driven rearomatization.