Kachur Alexander V, Arroyo Alejandro D, Bryan Nikaela W, Saylor Sarah J, Popov Anatoliy V, Delikatny E James
Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Department of Chemistry and Biochemistry, Misher College of Arts and Sciences, University of the Sciences, Philadelphia, PA 19104.
J Fluor Chem. 2017 Aug;200:146-152. doi: 10.1016/j.jfluchem.2017.06.017. Epub 2017 Jul 5.
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 -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 ( 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.
在有机合成中，使用分子氟气进行直接亲电氟化反应，以制备具有潜在有益活性的新型含氟化合物，而这些化合物无法通过亲核取代反应获得。在本文中，我们报道了在芳香体系中氟对溴的一种新型亲电取代反应。利用溴百里酚磺酞（溴百里酚蓝）与稀氟气在酸性条件下的反应，探索了这类氟化反应的机理。取代反应发生在相对于羟基处于邻位的溴原子上。对百里酚磺酞（百里酚蓝）进行类似的亲电氟化反应，会导致相同位置（相对于羟基）的氢原子被取代。利用核磁共振光谱法确认了氟化位点。在碱性条件下，百里酚磺酞及其衍生物的核磁共振光谱可通过考虑两个酚环之间不存在共振来解释。二溴百里酚蓝和氟溴百里酚蓝在其最大吸收波长附近均选择性地呈现出分子间衰减切伦科夫辐射，且该辐射与pH值有关。
