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.   第一作者简介： 陈定奔，台州学院副教授，从2014年9月开始，在本课题组进行博士后研究。主要研究亲核氟烷基化反应及其机理。