The Use of Fluoride as a Leaving Group: SN2′ Displacement of a CF Bond on 3,3-Difluoropropenes with Organolithium Reagents To Give Direct Access to Monofluoroalkenes
Lithium is the key to activate the nucleofuge ability of fluoride in the title transformation (see scheme). This simple and straightforward approach not only provides a practical synthetic method for the preparation of monofluoroalkenes, an important fluorinated motif, but also demonstrates the ability of fluoride to act as a competent leaving group in nucleophilic substitution reactions.
The superior nucleofuge character of chlorine over fluorine was taken advantage of in the selective SN2′ substitution reaction of gem-chlorofluoropropenes, allowing for the clean formation of β-substituted monofluoroalkenes under metal-free conditions. Numerous N-, S-, O-, and C-nucleophiles behaved nicely in this system. Further synthetic transformations of selected monofluoroalkenes were also accomplished
在宝石-氯氟丙烯的选择性S N 2'取代反应中,利用了氯优于氟的核沉子特性,从而可以在无金属的条件下干净地形成β-取代的单氟烯烃。在该系统中,许多N-,S-,O-和C-亲核试剂表现良好。还完成了所选单氟烯烃的进一步合成转化。