10.1021/jo102386s.s001 Khalid B. Selim Khalid B. Selim Hirotsugu Nakanishi Hirotsugu Nakanishi Yasumasa Matsumoto Yasumasa Matsumoto Yasutomo Yamamoto Yasutomo Yamamoto Ken-ichi Yamada Ken-ichi Yamada Kiyoshi Tomioka Kiyoshi Tomioka Chiral N-Heterocyclic Carbene−Copper(I)-Catalyzed Asymmetric Allylic Arylation of Aliphatic Allylic Bromides: Steric and Electronic Effects on γ-Selectivity American Chemical Society 2011 carbene ligand aryl group selectivity aryl Grignard reagents aliphatic allylic bromides Aliphatic Allylic Bromides 2011-03-04 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Chiral_N_Heterocyclic_Carbene_Copper_I_Catalyzed_Asymmetric_Allylic_Arylation_of_Aliphatic_Allylic_Bromides_Steric_and_Electronic_Effects_on_Selectivity/2686627 Chiral N-heterocyclic carbene ligands were electronically and sterically tuned to improve γ-selectivity in copper(I)-catalyzed asymmetric allylic arylation of aliphatic allylic bromides with several aryl Grignard reagents. High γ-selectivity was realized when either the aryl group of the Grignard reagent or the aryl group on the N-substituent of the carbene ligand was electron-deficient or when either the carbene ligand or allylic bromide was bulky. The results indicated that electron deficiency and steric hindrance of the initially formed σ-allyl copper intermediate enhance the rate of the reductive elimination to give γ-products as major isomers.