Synthesis of Five-Membered Ring Systems Bearing <i>gem</i>-Difluoroalkenyl and Monofluoroalkenyl Substituents via Radical β-Bromo Fragmentation
Peng Xu, Constantin G. Daniliuc, Klaus Bergander, Colin Stein, Armido Studer
Abstract
Fluoroalkenes are useful scaffolds in several areas, including drug development, the design of functional materials, and crop protection. Considering the importance of these fluoroalkenes, significant effort has been devoted to their synthesis; however, fast access to structurally diverse fluoroalkenes still remains a challenge. Herein, we report a radical β-bromo fragmentation approach to fluoroalkene moieties from terminal alkynes and gem-dibromofluoroalkanes, applying a well-designed photoinduced sequential radical addition–translocation–cyclization–fragmentation process. A series of structurally diverse, highly substituted five-membered ring systems with gem-difluoroalkenyl and monofluoroalkenyl side chains were prepared using this approach. The reaction proceeds efficiently under an air atmosphere at room temperature and benefits from easily available starting materials, a broad scope, and a good functional group tolerance.