Transition‐Metal‐Free Controllable Single and Double Difluoromethylene Formal Insertions into C−H Bonds of Aldehydes with TMSCF<sub>2</sub>Br
An Liu, Chuanfa Ni, Qiqiang Xie, Jinbo Hu
Abstract
Abstract We have developed a new strategy for controllable single and double difluoromethylene (CF 2 ) formal insertions into C−H bonds of aldehydes with nearly full selectivity under transition‐metal‐free conditions. The key to the success of controllable CF 2 insertions lies in the well‐defined formation of 2,2‐difluoroenolsilyl ether and 2,2,3,3‐tetrafluorocyclopropanolsilyl ether intermediates using difluorocarbene reagent TMSCF 2 Br (TMS=trimethylsilyl). These two intermediates can react with various electrophiles including proton sources and various halogenation reagents, allowing for the access to diverse arrays of ketones containing difluoromethylene (CF 2 ) and tetrafluoroethylene (CF 2 CF 2 ) units. The first synthesis of relatively stable 2,2,3,3‐tetrafluorocyclopropanolsilyl ethers has been achieved, which offers a new platform to explore other unknown chemical space.