Gallic acid-derived palladium(0) nanoparticles as in situ-formed catalyst for Sonogashira cross-coupling reaction in ethanol under open air

A simple and eco-friendly protocol using gallic acid-derived palladium(0) nanoparticles as in situ-formed catalyst for Sonogashira reactions in ethanol under optimum thermal conditions have been developed. Excellent yields were obtained with the addition of a small amount of gallic acid (1 mol%) to the reaction mixture. The formation of the PdNPs was confirmed by using UV/Vis spectroscopy, and their size and morphology were determined by TEM and XRD analysis. Both aliphatic and aromatic terminal alkynes displayed efficient reactivity with the catalytic system. Moreover, the reaction condition is highly compatible with less reactive aryl bromides at moderate temperature, and further can be reused repeatedly up to four cycles. Since gallic acid is a non-toxic naturally abundant phytochemical, the present method provides an efficient alternative route for Sonogashira reaction with natural feedstock as additive.