Direct electrophilic fluorination using molecular fluorine gas is used in organic synthesis to create novel fluorine-containing compounds with potential beneficial activity that could not be obtained by nucleophilic substitution. In this paper, we report a novel electrophilic substitution of bromine by fluorine in an aromatic system. The mechanism of this type of fluorination was explored using the reaction between bromothymolsulfonphthalein (Bromothymol Blue) and dilute fluorine gas under acidic conditions. Substitution occurs in the bromine atoms located in the ortho-position relative to the hydroxyl group. A similar electrophilic fluorination of thymolsulfonphthalein (Thymol Blue) leads to a substitution of hydrogen atoms in the same position (ortho to hydroxyl). NMR spectroscopy was used to confirm the fluorination sites. NMR spectra of thymolsulfonphthalein and its derivatives under basic conditions can be explained by considering the absence of resonance between the two phenolic rings. Both dibromothymol blue and fluorobromothymol blue revealed intermolecular attenuate Cerenkov radiation selectively near their maximum absorbance in a pH dependent manner.

中文翻译：

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通过在芳族体系中用氟进行溴的亲电取代，合成用于切伦科夫成像的pH指示剂。

使用分子氟气的直接亲电氟化用于有机合成中，以产生具有潜在有益活性的新型含氟化合物，而亲核取代无法获得这种潜在的有益活性。在本文中，我们报道了芳香体系中氟对溴的新型亲电取代。使用溴百里酚磺酞（溴百里酚蓝）和稀氟气在酸性条件下的反应，探索了这种氟化的机理。取代发生在相对于羟基位于邻位的溴原子中。百里香酚酞（百里香酚蓝）的相似的亲电氟化导致相同位置（邻位为羟基）的氢原子取代。NMR光谱用于确认氟化位点。可以通过考虑两个酚环之间不存在共振来解释百里香酚酞及其衍生物在碱性条件下的NMR谱。二溴百里酚蓝和氟溴百里酚蓝都显示出分子间的切伦科夫辐射选择性地以最大pH依赖的方式接近其最大吸光度。