Highly Selective Synthesis of Hydrosiloxanes by Au-Catalyzed Dehydrogenative Cross-Coupling Reaction of Silanols with Hydrosilanes

We report a highly selective synthesis of siloxane building blocks containing SiH2 or SiH functionalities. AuCl-(PPh3)/PPh3 or AuCl(PPh3)/(PBu3)-Bu-n system catalyzed the reaction of trihydrosilanes with silanols giving SiHrcontaining siloxanes exclusively. On the other hand, a highly selective reaction of dihydrosilanes with silanols to afford SiH-containing siloxanes was achieved by simply changing the phosphine ligand to a bidentate one, xantphos. Usefulness of SiH2-containing siloxanes was demonstrated by the synthesis of a trisiloxane, Et3SiOSi(Ph)(H)(OSiBuMe2)-Bu-t, and a pentasiloxane, Ph2Si-(OSiHPhOSiEt3)(2,) bearing SiH functionalities.