Regio- and Stereoselective Addition to gem -Difluorinated Ene-Ynamides: Access to Stereodefined Fluorinated Dienes.

The first synthesis of gem -difluorinated ene-ynamides is presented via deprotonation of trifluoromethylated N -allenamides and δ extrusion of fluorine. These highly reactive building blocks, owing to their dual functional groups, offer a unique entry to difluorinated dienes and to stereodefined, monofluoro-substituted dienes. Stereoselective addition to the ynamide moiety led to difluorinated dienes. A stereocontrolled domino δ elimination reaction followed by an addition/elimination sequence from trifluoromethylated N -allenamides provided exclusively stereodefined monofluorinated ene-ynamides.