Water mediated Heck and Ullmann couplings by supported palladium nanoparticles: importance of surface polarity of the carbon spheres

Abstract

Heterogeneous palladium nanoparticle catalysts that are supported on amphiphilic carbon spheres (Pd@CSP) have been utilized for water-mediated Heck coupling reactions of aryl halides with different alkenes under phosphine free as well as aerobic conditions. Furthermore, a variety of Heck coupling reactions using different bases and solvents, including organic polar and non-polar solvents, have been explored. Aryl bromides are also well activated in Heck coupling reactions in organic polar solvent and as well as in water. In addition, Ullmann coupling reactions of aryl iodides have been catalyzed in water with the aid of phase transfer catalysts (PTC) in moderate yields. A plausible mechanism for the catalytic activity of Pd@CSP in the case of the Ullmann reaction is also established. It has been demonstrated that the hydrophobic effects of the catalyst surface play an important role in catalyst activity in water. In addition, the E-factor analysis verified that our present protocol is significantly comparable with other catalytic systems and explains the improved greenness. Moreover, the catalyst described in this process is not only greener, but also retains its significant activity for up to four catalytic cycles for the Heck coupling reactions. The surface polarity of the amphiphilic carbon spheres results in higher activity under these conditions. † Electronic supplementary information (ESI) available. See

Efficient C--C cross-coupling reactions by (isatin)-Schiff base functionalized magnetic nanoparticle-supported Cu(II) acetate as a magnetically recoverable catalyst

“…48 At the end of the reaction, the mixture was cooled to room temperature and the catalyst was isolated by magnetic decantation. The recovered catalyst was thoroughly rinsed with ethyl acetate and distilled water, dried at room temperature, and used without any pretreatment for the next runs.…”

Synthesis and catalytic properties of highly branched palladium nanostructures using seeded growth

“…In industry, palladium is used extensively as a heterogeneous catalyst, especially for the reduction of automobile emissions, 1 and for carbon-carbon cross-coupling reactions such as Suzuki, [2][3][4][5] Heck, 6,7 and Stille coupling. 8,9 Suzuki cross-coupling reactions are one of the most widely implemented methods used in the formation of carbon-carbon bonds, and are also very efficient under heterogeneous catalysis conditions.…”

Recyclable glucose-derived palladium(0) nanoparticles as in situ-formed catalysts for cross-coupling reactions in aqueous media

“…Importantly, it was not necessary to wash the aqueous mixture to remove excess salts or base. 39 This study showed that the in situ formed palladium nanoparticles were recyclable for up to three cycles without significant loss of catalytic activity. A fifth reaction catalysed by the same palladium(0) nanoparticles gave the product in 61% yield.…”