Monitoring electrophilic intermediates in reactions of thiols in aqueous solution directly with F NMR.

Mechanistic studies of thiol reactivity can be challenging because electrophilic reaction intermediates, such as sulfenic acids (RSOH) and sulfenyl chlorides (RSCl), are generally too reactive to be observed directly. Herein we report the design and synthesis of a sterically-encumbered fluorinated triptycene thiol which enables direct observation of reaction intermediates in aqueous buffer by F NMR, as demonstrated in reactions with hydrogen peroxide and hypochlorous acid. Reactions with HO resulted in the formation of a persistent RSOH species, which was subsequently converted to a sulfinic acid (RSOH) and then a sulfonic acid (RSOH), while RSCl was found to be the intermediate in reactions with HOCl.