A Fluorescent Palladium-Ligand Platform for In Situ Monitoring and Bayesian Optimization of Sonogashira Coupling Reactions.

Palladium-catalyzed coupling reactions are indispensable tools for carbon-carbon bond formation, yet their optimization and real-time monitoring remain challenging in homogeneous catalytic systems. Herein, we report a multifunctional fluorescent ligand, (E)-N'-((1H-benzo[d][1,2,3]triazol-6-yl)methylene)-4-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)benzohydrazide (BTACB), which integrates palladium coordination, catalytic activity, and intrinsic fluorescence reporting within a single molecular framework. BTACB exhibits strong fluorescence emission at 518 nm and undergoes efficient and selective quenching upon coordination with Pd (II). The BTACB-Pd (II) complex is an effective catalyst for Sonogashira coupling. By combining the in situ fluorescence monitoring system with the Bayesian optimization-random forest model, the optimal reaction conditions can be quickly determined using the time-resolved fluorescence data derived from experiments. Under the optimized conditions, the coupling reaction continued with a yield as high as 99%. It is worth noting that the fluorescence of BTACB is strongly suppressed during the catalytic process and recovers after the reaction is completed, thus achieving continuous, noninvasive, and real-time monitoring of the catalytic process. This work presents a universal strategy in which the catalytically active fluorescent ligand serves as the reaction medium simultaneously. The in situ fluorescence monitoring and machine-learning-assisted optimization data interface provide a new paradigm for the intelligent regulation of palladium catalytic reactions.