Palladium nanoparticles, stabilized by lignin, as catalyst for cross-coupling reactions in water

Palladium nanoparticles of a definite shape (spherical) and dimension (8–14 and 16–20 nm) were prepared employing two water soluble lignin samples as both reducing and stabilizing agent in definitely green experimental conditions, namely aqueous solution, aerobic conditions, moderate temperature, short times. The above nanoparticles were employed as catalyst for a series of carbon–carbon coupling reactions carried out in water at mild conditions. Heck and Suzuki reactions were performed for several substrates, by changing the nature of halogen, the substituents at the aromatic ring, the bases employed and the temperature. Product yields were satisfactory and selectivities very good. Other two cross-coupling reactions, namely Sonogashira and Stille, were also tested: iodine derivatives showed always the best reactivity, while chlorine derivatives did not react.