Steric tuning of C 2-symmetric chiral N-heterocyclic carbene in gold-catalyzed asymmetric cyclization of 1,6-enynes

Steric tuning of C 2-symmetric chiral N-heterocyclic carbene (NHC) was performed in Au(I)-catalyzed asymmetric cyclization of 1,6-enyne. Higher enantioselectivity was realized when chiral NHC-AuCl/AgSbF 6 catalysts whose N-substituent on the NHC overlays the Au-Cl bond was utilized. © 2012 Elsevier Ltd. All rights reserved.