REGIOSELECTIVE HYDROSILATIONS .1. THE HYDROSILATION OF ALPHA,OMEGA-DIHYDROGEN FUNCTIONAL OLIGOPOLYDIMETHYLSILOXANES WITH 3-VINYL-7-OXABICYCLO[4.1.0]HEPTANE

The hydrosilation of alpha,omega-dihydrogen functional oligopolydimethylsiloxanes with epoxy compounds containing vinyl groups has been found to take place regioselectively in such a manner that compounds can be isolated in high yields in which only one Si - H group has been reacted. Three different a,w-dihydrogen functional oligopolydimethysiloxanes with different chain lengths were monohydrosilated and the resulting epoxide monomers characterized. The rate of hydrosilation at the first Si - H functional group has been shown to be considerably faster than at the second site and from these kinetic studies, activation energies for each hydrosilation step were calculated. Mechanisms are considered which offer an explanation for these observations. (C) 1993 John Wiley & Sons, Inc.