Synthesis of deuterium and tritium labeled 2‐acetamido‐ 5,6‐dimethylbenzimidazole

Abstract Synthesis of 2‐acetamido‐5,6‐dimethylbenzimidazole, labeled with deuterium and tritium at the 4‐ and 7‐Dositions of the benzimidazole ring system, is described. 4,5‐Dimethyl‐O‐phenyl‐enediamine is deuterated and tritiated in the 3‐ and 6‐positions by means of exchange with deuterated and tritiated water. These relatively labile labels are rendered stable after formation of the benzimidazole rinq system. The stability of the labels in 2‐acetamido‐5,6‐dimethyl[4,7‐3H]benzimidazole is ascertained.