KCN-Catalyzed C–C Bond Formation between Imine and gem-Difluoroalkene Moieties: A Facile Synthesis of 2,4-Disubstituted 3-Fluoroquinolines

Intramolecular cyclization of (beta),(beta)-difluoro-o-methyleneaminostyrenes leading to 3-fluoroquinolines is efficiently promoted by a catalytic amount of KCN and a small excess of K2CO3. The reaction proceeds via (i) the generation of intramolecular carbon nucleophiles from imine moieties and (ii) the cyclization by their substitution for the vinylic fluorine.