Fluorogenic Coumarins Activated via Bioorthogonal Reactions.

Fluorogenic bioorthogonal reagents enable facile detection in complex environments. While useful for real-time imaging, few such probes are available. Existing tools also exploit similar mechanisms for signal turn-on, precluding multiplexed applications. To address these gaps, we developed a palette of cyclopropenone (CpO) scaffolds that are activated by bioorthogonal phosphines to produce coumarins. The top CpO-phosphine pairs show strong fluorescent enhancements (up to 760-fold), high quantum yields, and stability in aqueous environments. The CpO fluorogens also exhibit unique reaction profiles, setting the stage for multicomponent labeling studies.