The Suzuki-Miyaura coupling is one of the most frequently used reactions in organic synthesis. However, there have been several attempts to develop palladium-free conditions because of its cost and toxicity. The sensitivity of these reactions towards parts per billion amounts of Pd present in the reaction mixture makes it difficult to overrule the presence of an active Pd species. We developed a simple and general methodology for the identification of trace Pd impurities and their role in reactions for both industrial applications and academic integrity. This step-by-step purification strategy combined with the fluorometric quantification of Pd confirmed the linear correlation between trace palladium impurity and reaction rate in a reported amine-catalyzed cross-coupling reaction. Also, our mass spectroscopic analysis of the arylamine revealed the presence of a palladium-phosphine complex. When Pd(OAc)<sub>2</sub> was used as a catalyst for the same Suzuki-Miyaura coupling, we found that tricyclohexylphosphine ligand was detrimental to the coupling and that the arylamine played negligible role. This study demonstrates the utility of the fluorometric technology for catalysis research.

Fluorometric study on the amine-catalyzed Suzuki-Miyaura coupling

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