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首页> 外文期刊>Chemistry: A European journal >Unexpected Behavior of the Heaviest Halogen Astatine in the Nucleophilic Substitution of Aryliodonium Salts
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Unexpected Behavior of the Heaviest Halogen Astatine in the Nucleophilic Substitution of Aryliodonium Salts

机译：最重的卤素A在Aryliodonium盐的亲核取代中的意外行为

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摘要

Aryliodonium salts have become precursors of choice for the synthesis of F-18-labeled tracers for nuclear imaging. However, little is known on the reactivity of these compounds with heavy halides, that is, radioiodide and astatide, at the radiotracer scale. In the first comparative study of radiohalogenation of aryliodonium salts with I-125(-) and At-211(-), initial experiments on a model compound highlight the higher reactivity of astatide compared to iodide, which could not be anticipated from the trends previously observed within the halogen series. Kinetic studies indicate a significant difference in activation energy (E-a=23.5 and 17.1kcalmol(-1) with I-125(-) and At-211(-), respectively). Quantum chemical calculations suggest that astatination occurs via the monomeric form of an iodonium complex whereas iodination occurs via a heterodimeric iodonium intermediate. The good to excellent regioselectivity of halogenation and high yields achieved with diversely substituted aryliodonium salts indicate that this class of compounds is a promising alternative to the stannane chemistry currently used for heavy radiohalogen labeling of tracers in nuclear medicine.
机译：金盏花盐已成为合成用于核成像的F-18标记示踪剂的首选前体。然而，在放射性示踪剂规模上，这些化合物与重卤化物，即放射性碘化物和a化物的反应性知之甚少。在用I-125（-）和At-211（-）进行芳基碘鎓盐的放射性卤代作用的第一个比较研究中，对模型化合物的初步实验突出了a素比碘化物具有更高的反应性，这不能从以前的趋势中预测到在卤素系列中观察到。动力学研究表明，活化能存在显着差异（分别为I-125（-）和At-211（-）的E-a = 23.5和17.1kcalmol（-1）。量子化学计算表明，stat化通过碘鎓络合物的单体形式发生，而碘化通过异二聚碘鎓中间体发生。用不同取代的芳基碘鎓盐实现的卤代区域选择性良好且产率高，表明此类化合物是目前用于核医学示踪剂重放射性卤素标记的锡烷化学的有前途的替代品。

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