Ruthenium-catalyzed hydrosilylation of terminal alkynes: stereodivergent synthesis of (E)- and (Z)-alkenylsilanes

Stereodivergent hydrosilylation of terminal alkynes (RCCH; R=Ph, p-tolyl, Cy, n-hexyl) with hydrosilanes (HSiMe2Ar; ArPh, 3,5-(CF3)2C6H3, 4-CF3C6H4, 4-MeOC6H4) has been examined using ruthenium catalysts. (E)-selective reactions giving (E)-RCHCHSiMe2Ar proceed in over 99% selectivity in the presence of a catalytic amount of RuHCl(CO)(PPh3)3. On the other hand, (Z)-selective reactions are successfully conducted in 91–99% selectivity by using Ru(SiMe2Ph)Cl(CO)(PPr3i)2 as the catalyst. All reactions readily proceed at room temperature in high yields. (E)- and (Z)-styrylsilanes having a SiMe2[C6H33,5-(CF3)2] group serve as good cross-coupling reagents with p-iodotoluene in the presence of tetrabutylammonium fluoride and [Pd(η3-allyl)Cl]2 catalyst.