An efficient and new protocol for the Heck reaction using palladium nanoparticle-engineered dibenzo-18-crown-6-ether/MCM-41 nanocomposite in water

Palladium nanoparticle-incorporated mesoporous organosilica (MCM-41-Crown.Pd) was synthesized via the grafting of dibenzo-18-crown-6-ether moieties on the MCM-41 surface, followed by reaction of the nanocomposite with palladium acetate and then its reduction in ethanol. The cavity of the immobilized dibenzo-18-crown-6 as host material can stabilize the palladium nanoparticles effectively and prevent their aggregation and separation from the surface. The structure of the nanocomposite was characterized using various techniques. The catalytic properties of the nanocomposite in the Heck coupling reaction, one of the most useful transformations in organic synthesis, between aryl halides and olefins in water were also explored. The main advantages of the method are low cost, high yields, easy work-up and short reaction time. The nanocatalyst can be easily separated from a reaction mixture and was successfully examined for seven runs, with a slight loss of catalytic activity.