Facile access to α-silylmethylamidines by BF3-catalyzed hydroamination of silylynamides with amines†

The metal-free BF₃-catalyzed hydroamination of silylynamides with amines allows facile and efficient synthesis of α-silylmethylamidines in moderate to excellent yields (up to 99%) with a broad substrate scope and excellent functional group compatibility under mild reaction conditions. This protocol offers the first synthetic route to silyl-incorporated amidine compounds, which features the use of Lewis acid BF₃ as the catalyst and easily available silylynamides as the silicon source. Considering the biological importance of amidine scaffolds and silyl groups, the easy incorporation of these two structural units should make great sense for medicinal chemistry. Notably, with this strategy, the installation of amidine scaffolds to drug-like molecules celecoxib and estrone is realized for the first time. A plausible mechanism involves the formation of vinyl-boron intermediates from BF₃-activated ynamides, which after protodeboronation and tautomerization afford the desired products.