Stereoselective Ring-Opening of gem-Difluorocyclopropanes: An Entry to Stereo-defined (E,E)- and (E,Z)-Conjugated Fluorodienes.

The ring-opening of gem-difluorocyclopropyl acetaldehydes producing selectively (E,E)- and (E,Z)-conjugated fluorodienals is described. Two stereo-divergent methods are presented to access both stereoisomers from a common precursor, in high yield and selectivity. The mechanistic aspect of these transformations is discussed.