K2CO3-activated Hydrosilylation: from Redistribution of Polymethylhydrosiloxane to Selectively Reduction of Aldehydes and Ketones

Abstract

The hydrosilylation reduction of aldehydes and ketones to the corresponding alcohols with polymethylhydrosiloxane (PMHS) as hydrosilanes in the presence of potassium carbonate (K2CO3) has been developed. This Lewis base protocol displays excellent chemoselectivity and can tolerate a number of other reducible functionalities like nitro, sulfone, cyano, alkene, as well as ester. In order to make the mechanism of PMHS based hydrosilylation more clearly, we have isolated the silyl ether intermediates. We find that the PMHS is redistributed into methylsilane (H3SiMe) and a series of siloxanes in the structures of H2SiMeO(SiHMeO)nSiMeH2 (n=0, 1, 2,……), which serve as the active hydrosilanes for the hydrosilylation reaction.