Regioselective Hydrosilylation of Unsymmetrical Aryl Alkynes

Significance

The PtO₂-catalyzed hydrosilylation of unsymmetrical aryl alkynes gave preferentially the α-silylated product when an ortho-substituent on the aryl group was present, regardless of whether the ortho-substituent was an electron-donating or electron-withdrawing one. para-Substituents showed a weaker α-silylation directing effect. PtO₂ displayed a more powerful directing effect than H₂PtCl₆ and also resulted in higher yields since it does not promote alkyne reduction.