Bis(difluoromethyl)trimethylsilicate Anion: A Key Intermediate in Nucleophilic Difluoromethylation of Enolizable Ketones with Me3SiCF2H  Chen, Dingben; Ni, Chuanfa; Zhao, Yanchuan; Cai, Xian; Li, Xinjin; Xiao, Pan; Hu, Jinbo* Angew. Chem., Int. Ed. 2016, 55, 12632 – 12636.

　　 

Abstract：

　　       A pentacoordinate bis(difluoromethyl)silicate anion, [Me₃Si(CF₂H)₂]^-, is observed for the first time by the activation of Me₃SiCF₂H with a nucleophilic alkali-metal salt and 18-crown-6. Further study on its reactivity by tuning the countercation effect led to the discovery and development of an efficient, catalytic nucleophilic difluoromethylation of enolizable ketones with Me₃SiCF₂H by using a combination of CsF and 18-crown-6 as the initiation system. Mechanistic investigations demonstrate that [(18-crown-6)Cs]⁺[Me₃Si(CF₂H)₂]^- is a key intermediate in this catalytic reaction.