Mechanistic Insight into the (NHC)copper(I)-Catalyzed Hydrosilylation of Ketones

(NHC)­copper­(I)
hydride catalyzed ketone hydrosilylation is an efficient
method for the enantioselective synthesis of secondary alcohols. Herein,
we represent a computational study of this reaction using density
functional theory (DFT) on realistic model systems. This study is
supported by kinetic investigations, using in situ FTIR measurements.
The calculations validate the previously proposed reaction mechanism
and explain the high activity of (OR1)xR23–xSi–H
types of silanes. Experimental evidence in favor of the monomeric
(NHC)­CuH form of the catalyst is also given. Combining experimental
and theoretical results furthermore highlights a Lewis base activation
of the hydrosilane, leading to a modified suggestion for the mechanistic
scheme of the catalytic cycle.