A new and efficient synthesis of monotritiomethyl iodide

A new and efficient synthesis of high specific activity TCH2I containing one atom of tritium per molecule is reported. The precursors for this reagent, chloromethyl p-phenylbenzoate or bis-chloromethyl terephthalate, were prepared by the condensation of the corresponding acid chlorides with paraformaldehyde in the presence of zinc chloride. Tritiodehalogenation of the precursors with tritium gas and Pd-C(10%) in dimethylformamide afforded the desired tritioesters. Cleavage of the esters by lithium iodide at 1800C (SN2 type reaction), or by HI at 1400C gave mono tritium labeled methyl iodide in more than 95% yield. The reaction of the latter with a number of amines yielded tritium labeled N-methylated products readily as was shown by Radio-HPLC. The specificity of the labeling in the final products was confirmed by tritium nmr spectroscopy. (author)