Chiral N-Heterocyclic Carbene−Copper(I)-Catalyzed Asymmetric Allylic Arylation of Aliphatic Allylic Bromides: Steric and Electronic Effects on γ-Selectivity
Khalid B. Selim
Hirotsugu Nakanishi
Yasumasa Matsumoto
Yasutomo Yamamoto
Ken-ichi Yamada
Kiyoshi Tomioka
10.1021/jo102386s.s001
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.
2011-03-04 00:00:00
carbene ligand
aryl group
selectivity
aryl Grignard reagents
aliphatic allylic bromides
Aliphatic Allylic Bromides