Chiral N-heterocyclic carbene-copper(I)-catalyzed asymmetric allylic arylation of aliphatic allylic bromides: steric and electronic effects on γ-selectivity.
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.
Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt.
Khalid B
KB
Selim
Hirotsugu
H
Nakanishi
Yasumasa
Y
Matsumoto
Yasutomo
Y
Yamamoto
Ken-ichi
K
Yamada
Kiyoshi
K
Tomioka
D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D004583:Electrons; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006842:Hydrocarbons, Brominated / Q000138:chemical synthesis* / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism
D006571:Heterocyclic Compounds; D006842:Hydrocarbons, Brominated; D009942:Organometallic Compounds; C030011:carbene; D003300:Copper; D008697:Methane