A simple and efficient Suzuki reaction catalyzed by palladium-modified nanopore silica under solvent-free conditions

In this paper our recent results of the Suzuki reaction using [Pd(NH3)4]2+-modified nanopore silica under solvent-free conditions are described. [Pd(NH3)4]2+-modified nanopore silica was prepared by impregnation using an aqueous solution of [Pd(NH3)4]Cl2 in water or in acetonitrile. The BET surface area, BJH mean pore diameter and pore volume are 138.8 m2/g, 8.7 nm, and 0.34 cm3/g, respectively, and the pore size distribution shows a single peak at around 5 nm in diameter. It has been shown that the Suzuki reaction is performed in excellent yield by using Pd-modified nanopore silica under solvent-free conditions heated at 90–100 °C for 3–5 h. It has been found that aryl bromides can be coupled with aryl boronic acids in excellent yield under solvent-free condition. Phenyl iodide was also coupled with phenyl boronic acids in excellent yield, whereas phenyl chloride gave product in poor yield. And KF, CsF or Bu4NF were also found to be a convenient base additive.