PLATINUM CATALYZED HYDROSILYLATION OF ALKYNES - COMPARISON OF RATES OF ADDITION OF TERMINAL OLEFINS TO INTERNAL ALKYNES

The relative rates of platinum catalyzed hydrosilylation of terminal olefins versus internal alkynes were compared in competitive reactions. (EtO)3SiH added almost exclusively (97%) to PhC = CPh versus styrene. The reaction of (EtO)3SiH with equimolar amounts of 2-decyne and 1-hexene gave a 78:22 ratio of alkyne products 6/6' versus alkene product 7. The reaction of (EtO)3SiH with equimolar amounts of styrene and 1-phenyl-1-propyne gave a 78:22 ratio of alkyne products 10/10' to products 9. The silane, Me3SiOSiMe2H, reacted with equimolar amounts of 2-decyne and 1-hexene to give a 90:10 ratio of alkyne products 8/8' to alkene product 9. All of the products had E stereochemistry about the C = C double bond as determined by Si-29 NMR (3J(Si-H)).