Metal-free synthesis of gem -difluorinated heterocycles from enaminones and difluorocarbene precursors.

A cascade strategy to synthesise gem -difluorinated 2 H -furans from reactions of BrCF 2 CO 2 Et with enaminones has been described. The reactions tolerate a wide variety of functional groups under metal-free conditions. An active aminocyclopropane is proposed to be a key intermediate through the cyclopropanation of difluorocarbene with enaminones, which further triggers a regioselective C-C bond cleavage in situ to afford the corresponding gem -difluorinated 2 H -furans.