Catalytic dehalogenation of aromatic halides using isotopic hydrogen gas is an important strategy for labelling pharmaceuticals, biochemicals, environmental agents and so forth. To extend, improve and further understand this process, studies have been carried out on the scrambling of deuterium isotope with protium during the catalytic deuterodehalogenation of model aryl chlorides using deuterium gas and a palladium on carbon catalyst in tetrahydrofuran solution. The degree of scrambling was greatest with electron‐rich chloroarene rings. The tetrahydrofuran solvent and the triethylamine base were not the source of the undesired protium; instead, it arose, substantially, from the water content of the catalyst, though other sources of protium may also be present on the catalyst. Replacement of the Pd/C catalyst with one prepared in situ by reduction of palladium trifluoroacetate with deuterium gas and dispersed upon micronised polytetrafluoroethylene led to much reduced scrambling (typically 0–6% compared with up to 40% for palladium on carbon) and to high atom% abundance, regiospecific labelling. The improved catalytic system now enables efficient polydeuteration via the dehalogenation of polyhalogenated precursors, making the procedure viable for the preparation of MS internal standards and, potentially, for high specific activity tritium labelling.

中文翻译：

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在钯催化剂上用氘气脱卤芳族氯化合物过程中氢同位素扰乱的研究。

使用同位素氢气对芳族卤化物进行催化脱卤是标记药物、生物化学品、环境试剂等的重要策略。为了扩展、改进和进一步了解这一过程，在四氢呋喃溶液中使用氘气和钯碳催化剂对模型芳基氯进行催化氘代脱卤过程中，对氘同位素与氚的扰乱进行了研究。富电子氯芳烃环的加扰程度最大。四氢呋喃溶剂和三乙胺碱不是不想要的朊的来源；相反，它主要来自催化剂的水含量，尽管其他来源的朊也可能存在于催化剂上。用一种制备的催化剂代替 Pd/C 催化剂通过用氘气原位还原三氟乙酸钯并分散在微粉化聚四氟乙烯上，可显着减少乱序（通常为 0-6%，而碳载钯最高可达 40%）和高原子百分比丰度，区域特异性标记。改进后的催化系统现在可以通过多卤化前体的脱卤实现高效的多氘化，使该过程可用于制备 MS 内标，并可能用于高比活性氚标记。