Capturing the Monomeric (L)CuH in NHC-Capped Cyclodextrin: Cavity-Controlled Chemoselective Hydrosilylation of α,β-Unsaturated Ketones.

The encapsulation of copper inside a cyclodextrin capped with a N -heterocyclic carbene (ICyD) allowed both to catch the elusive monomeric (L)Cu-H and a cavity-controlled chemoselective copper-catalyzed hydrosilylation of α,β -unsaturated ketones. Remarkably, ( α -ICyD)CuCl promoted exclusively the 1,2-addition, while ( β -ICyD)CuCl produced the totally reduced product. The chemoselectivity is controlled by the size of the cavity and weak-interactions between the substrate and internal C-H of the cyclodextrin.