| Autor: |
Keddie NS; School of Chemistry, Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom., Champagne PA; PROTEO, CCVC, Département de chimie, 1045 Avenue de la Médecine, Université Laval, Québec, QC G1V 0A6, Canada., Desroches J; PROTEO, CCVC, Département de chimie, 1045 Avenue de la Médecine, Université Laval, Québec, QC G1V 0A6, Canada., Paquin JF; PROTEO, CCVC, Département de chimie, 1045 Avenue de la Médecine, Université Laval, Québec, QC G1V 0A6, Canada., O'Hagan D; School of Chemistry, Biomedical Sciences Research Complex, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom. |
| Abstrakt: |
In recent years, the highly polar C-F bond has been utilised in activation chemistry despite its low reactivity to traditional nucleophiles, when compared to other C-X halogen bonds. Paquin's group has reported extensive studies on the C-F activation of benzylic fluorides for nucleophilic substitutions and Friedel-Crafts reactions, using a range of hydrogen bond donors such as water, triols or hexafluoroisopropanol (HFIP) as the activators. This study examines the stereointegrity of the C-F activation reaction through the use of an enantiopure isotopomer of benzyl fluoride to identify whether the reaction conditions favour a dissociative (S N 1) or associative (S N 2) pathway. [ 2 H]-Isotopomer ratios in the reactions were assayed using the Courtieu 2 H NMR method in a chiral liquid crystal (poly-γ-benzyl-L-glutamate) matrix and demonstrated that both associative and dissociative pathways operate to varying degrees, according to the nature of the nucleophile and the hydrogen bond donor. |
