gem-Difluorination of aminoalkynes via highly reactive dicationic species in superacid HF-SbF5:: Application to the efficient synthesis of difluorinated Cinchona alkaloid derivatives

A variety of alkynylated amines, amides, and imides are reacted in the superacid system HF-SbF5 to give regioselectively new beta-gem-difluoroamines. The reaction, which is not observed in pure HF, is consistent with the formation of a dicationic intermediate (i.e., both vinylic and adjacent protonated N-ammonium cations). Application to the regioselective and efficient synthesis of difluorinated cinchona alkaloid derivatives is described.