Synthesis of gem‐Difluoro Olefins through C−H Functionalization and β‐fluoride Elimination Reactions

A palladium catalyzed C−H functionalization and consecutive β‐fluoride elimination reaction between indole heterocycles and fluorinated diazoalkanes is reported. This approach provides for the first time a facile method for the rapid synthesis of gem‐difluoro olefins using fluorinated diazoalkanes under mild reaction conditions. Cyclopropanation products were obtained when N‐arylated rather than N‐alkylated indoles were applied in this reaction. Mechanistic studies reveal the importance of the β‐fluoride elimination step in this transformation. This method presents a new concept for the simple and direct transfer of a 1‐aryl‐(2,2‐difluorovinyl) group to access gem‐difluoro olefins.