Zinc/Indium Bimetallic Lewis Acid Relay Catalysis for Dehydrogenative Silylation/Hydrosilylation Reaction of Terminal Alkynes with Bis(hydrosilane)s

Abstract

AbstractWhen mixed with two different Lewis acid catalysts of zinc and indium, terminal alkynes were found to react with bis(hydrosilane)s to selectively provide 1,1‐disilylalkenes from among several possible products, by way of a sequential dehydrogenative silylation/intramolecular hydrosilylation reaction. Adding a pyridine base is crucial in this reaction; a switch as a catalyst of the zinc Lewis acid is turned on by forming a zinc−pyridine‐base complex. A range of the 1,1‐disilylalkenes can be obtained by a combination of aryl and aliphatic terminal alkynes plus aryl‐, heteroaryl‐, and naphthyl‐tethered bis(hydrosilane)s. The 1,1‐disilylalkene prepared here is available as a reagent for further transformations by utilizing its C−Si or C=C bond. The former includes Hiyama cross‐coupling, bismuth‐catalyzed ether formation, and iododesilylation; the latter includes double alkylation and epoxidation. Mechanistic studies clarified the role of the two Lewis acids: the zinc–pyridine‐base complex catalyzes the dehydrogenative silylation as a first stage, and, following on this, the indium Lewis acid catalyzes the ring‐closing hydrosilylation as a second stage, thus leading to the 1,1‐disilylalkene.magnified image