Carbonothioate‐Triggered Cascade Cyclization Enables High‐Specificity Fluorescence Imaging of Hydrogen Polysulfides

Hydrogen polysulfides (H 2 S n ; n > 1) are critical redox signaling molecules. While the biological functions of H 2 S n have received much attention, their exact action mechanisms are still poorly understood due to the lack of reliable detection methods. In this context, fluorescent probes for H 2 S n are emerging as powerful chemical tools to aid in unraveling its contributions to biology. Currently, most available H 2 S n probes are prone to interference from biothiols or hydrogen sulfide (H 2 S). To address this challenge, herein, we report a unique carbonothioate‐based trigger utilizing a cascade cyclization reaction for specific detection of H 2 S n . Using this strategy, eight new fluorescent probes ( CTP 1–8 ) were prepared and evaluated. Among them, CTP‐8 not only enables highly sensitive and selective detection of H 2 S n but also allows visualization of H 2 S n fluctuations in living cells and mice. Significantly, we demonstrate for the first time the fluorescence imaging of endogenous H 2 S n dynamics in insulin‐resistant cells and type 2 diabetes mellitus (T2DM) mice. Besides, this carbonothioate‐based trigger could also be potentially utilized in other fluorescent dye scaffolds that possess an optically tunable phenolic hydroxyl group. This work provides a useful approach for further investigations of H 2 S n biology as well as future probe development.