β‑Cyclodextrin–NHC–Gold(I) Complex (β-ICyD)AuCl: A Chiral Nanoreactor for Enantioselective and Substrate-Selective Alkoxycyclization Reactions

NHC-capped β-cyclodextrin (β-ICyD) was used as a ligand for gold-catalyzed alkoxycyclization reactions. The cavity was found to be responsible for a triple selectivity: (i) the asymmetric shape of the cavity of β-ICyD induced highly stereoselective cyclizations, (ii) the shape of the interior favored the formation of a six-membered ring in the absence of a nucleophile, and finally, (iii) the encapsulation of the metal inside the cavity disfavored the addition of sterically hindered alcohols. Highly enantioselective and substrate-selective alkoxycyclizations of enynes are therefore promoted by the cavity-based molecular reactor (β-ICyD)­AuCl.