Preparation of Oligomeric and Polymeric Alpha,Omega-Bis(trimethylsiloxy)polymethylchlorosiloxanes and Their Reactions with Alkyllithium Reagents

摘要

A series of alpha, omega-bis(trimethylsiloxy) polymethylchlorosiloxanes(MD superscript CL sub nM)(n=1-5 and approx.35) as well as MD superscript Cl D superscript HM have been prepared by the palladium on carbon-catalyzed exchange reaction of MD superscript H sub NM with allyl or benzyl chloride. The reaction of these with alkyllithium reagents in ether at -78C has been studied. Alkylation without cleavage of the siloxane backbone is observed with the oligomers MD superscript CL sub NM. On the other hand, MD superscript HM and MD superscript CL D superscript HM undergo facile siloxane cleavage. Some cleavage is also observed with the polymer MD superscript CL approx,35M. The spectral properties, in particular 1H, 13C, and 29Si NMR, of both MD superscript H sub nM and MD superscript CL nM are reported. The interpretation of the 134C and 29Si NMR spectra of siloxane oligomers which are chiral at both Si and C is discussed.