Borane-Catalyzed Selective Hydrosilylation of Internal Ynamides Leading to β-Silyl (Z)-Enamides.

We have developed a borane-catalyzed regio- and stereoselective hydrosilylation of internal ynamides for the first time. The scope of ynamide substrates and silane reactants was broad under mild reaction conditions, affording synthetically versatile β-silyl (Z)-enamide products. The observed stereoselectivity was reasoned to be due to the β-silicon effect on a postulated ketene iminium intermediate.