A highly efficient and selective fluorescent probe for Pd (II) based on benzotriazole-coumarin derivative and its catalytic application in Sonogashira reaction

Palladium-catalyzed coupling reactions have become effective tools for forming new carbon–carbon bonds. In this work, a novel fluorescence active benzotriazole-coumarin derivative, (E)-N'-((1H-benzo[d][1,2,3]triazol-6-yl)methylene)-7-(diethylamino)-2-ox o-2H-chromene-3-carbohydrazide (BTANC), was synthesized as ligand in Pd(II) cation coordination. It is shown that BTANC has a strong fluorescent emission at 483 nm and Pd(II) can effectively quench the fluorescence of BTANC and BTANC shows excellent sensitivity and selectivity towards Pd (II) ions. Otherwise, the BTANC-Pd(II) complex was also tested in the Sonogashira coupling reaction of phenylacetylene and aryl halides. The desired product was obtained with high yield (up to 99%) under the optimized reaction conditions. More to that, Low fluorescence emission was observed during the Pd-catalyzed reaction process and the fluorescent emission of BTANC was recovered at the end of the Pd-catalyzed reaction because the oxidative addition of the aryl halide towards Pd (0) was shut down at the end of the Pd-catalyzed reaction. This fluorescence properties of BTANC indicates the feasibility of using fluorescence signal as a potential tool to monitor the completion of the Sonogashira coupling reaction.