Chloride ion-catalyzed generation of difluorocarbene for efficient preparation of gem-difluorinated cyclopropenes and cyclopropanes

A chloride ion-catalyzed generation of difluorocarbene from a relatively non-toxic and inexpensive precursor, Me(3)SiCF(2)Cl (1), under mild and neutral conditions leads to an efficient preparation of gem-difluorocyclopropenes and difluorocyclopropanes through [2 + 1] cycloaddition reactions with alkynes and alkenes, respectively.