New method for the synthesis of difficultly available sterically hindered tritium-labeled pyridinium derivatives

Direct phenylation of the nitrogen atom in pyridines was noted in a study of the ion-molecule reactions of free nucleogenic phenyl cations generated by β-decay of tritium in labeled benzene. A one-step synthesis of unreported biologically active tritium-labeled N-phenyl-2,6-lutidinium and 2,4,6-collidi-nium salts. Steric factors, which significantly reduce the yield in the case of sym-collidine, play a major role in the direct phenylation of nitrogen.