Reversible C–H bond silylation with a neutral silicon Lewis acid

Abstract

The silicon–carbon bond is a valuable linchpin for synthetic transformations. However, installing Si–C functionalities requires metalated C-nucleophiles, activated silicon reagents (silylium ions, silyl radicals, and silyl anions), or transition metal catalysis, and it occurs irreversibly. In contrast, spontaneous C–H silylations with neutral silanes leading to anionic silicates, and their reversible deconstruction, are elusive. Herein, the CH-bond silylation of heterocycles or a terminal alkyne is achieved by reaction with bis(perfluoro(N-phenyl-ortho-amidophenolato))silane and 1,2,2,6,6-pentamethylpiperidine. Computational and experimental insights reveal a frustrated Lewis pair (FLP) mechanism. Adding a silaphilic donor to the ammonium silicate products induces the reformation of the C–H bond, thus complementing previously known irreversible C–H bond silylation protocols. Interestingly, the FLP “activated” N-methylpyrrole exhibits “deactivated” features against electrophiles, while a catalytic functionalization is found to be effective only in the absence of a base.