Abstract The enantioselective, organocatalytic aziridination of small, medium and macro- cyclic enals is reported using (S)-2-(fluorodiphenyl methyl)-pyrrolidine. Central to the reaction design is the reversible formation of a β-fluoroiminium ion intermediate, which is pre- organised on account of the fluorine-iminium ion gauche effect. This conformational effect positions the fluorine substituent synclinal-endo to the electropositive nitrogen centre thus ...
