Aminophosphine Palladium Pincer-Catalyzed Carbonylative Sonogashira and Suzuki-Miyaura Cross-Coupling with High Catalytic Turnovers.

Abstract

This work documents the first palladium pincer complex-catalyzed carbonylative Sonogashira (CS) and carbonylative Suzuki–Miyaura (CSM) cross-coupling. Compared to previous protocols, which employ hazardous and toxic solvents, the aminophosphine pincer complex {[C6H3-2,6-(NHP{piperidinyl}2)2]Pd(Cl)} (III) catalyzes both the cross-coupling reactions in propylene carbonate, an eco-friendly and sustainable polar aprotic solvent. Advantageously, employing III allows the CS cross-coupling to be carried out at a palladium loading of 10–4 mol % and the CSM cross-coupling to be carried out at 10–6 mol %, thus resulting in catalytic turnovers of 105 and 107, respectively. Relative comparison of the pincer complex with conventional palladium precursors Pd(OAc)2 and PdCl2(PPh3)2 shows the efficiency and robustness of the pincer complex in effecting higher catalytic activity at low palladium loadings.