A GENERAL-SYNTHESIS OF VERY HIGH SPECIFIC ACTIVITY TRITIOMETHYL IODIDE

A general synthesis of highly tritiated or deuteriated methyl iodide has been elaborated. Tritio-dehalogenation of trichloromethyl biphenyl-4-yl ether with tritium gas over Pd/C in ethyl acetate yields the corresponding tritiomethyl biphenyl-4-yl ether of very high specific activity. Reaction of this [3H]product with hydroiodic acid hydrolyses the ether, and quantitatively liberates tritiomethyl iodide. Alkylation of a secondary amine with freshly generated tritiomethyl iodide gives a high yield, and demonstrates the utility of the reagent. Radio-HPLC analysis of the intermediate labelled ether and the amine product showed complete radiochemical purity with full retention of specific activity, and the specificity of labelling was confirmed in both products by 3H NMR spectroscopy. Preparatory chemistry was performed with deuterium gas and the deuteriated reaction products, and analogous analyses performed by HPLC and 2H NMR spectroscopy.