Heck Heterocoupling within a Dendritic Nanoreactor

Abstract

Palladium nanoparticles (2−3 nm in diameter) have been prepared within covalently functionalized poly(propylene imine) (PPI) dendrimers, and the resulting composite materials are shown to be effective for Heck coupling reactions. Two novel concepts are demonstrated in this report. The first concept involves the incorporation of Pd 0 nanoparticles into PPI dendrimers covalently functionalized with perfluorinated polyether chains on their periphery. The second concept involves the first example of a carbon−carbon coupling reaction catalyzed by a dendrimer-templated nanomaterial, specifically, the catalytic heterocoupling between nonactivated aryl halides and n-butylacrylate mediated by the dendrimer-encapsulated catalysts. These reactions were carried out in a homogeneous fluorous/organic reaction phase at elevated temperature, and the catalyst was recovered by cooling to room temperature and concomitant phase separation. The catalyst was found to be catalytically active at a reaction temperature of only 90 °C in the absence of toxic phosphines, and it was 100% selective for the production of n-butyl-trans-formylcinnamate with unoptimized isolated yields up to 70%. The recovered catalysts retained a significant fraction of the original activity, comparable to coordination complex catalysts that use a similar catalyst recovery system.

Dendrimer-Encapsulated Metal Nanoparticles: Synthesis, Characterization, and Applications to Catalysis

“…9 The second illustrates the use of perfluoroether groups covalently linked to the exterior of PPI dendrimers to carry out a carbon-coupling Heck reaction. 7 In both cases the fluorous-soluble, dendrimer-based catalyst was recyclable. Moreover, the reactions resulted in selectivities and products that might reflect the unique nanoenvironment of the reaction volume defined by the dendrimer interior.…”

Recent Advances in the Liquid‐Phase Synthesis of Metal Nanostructures with Controlled Shape and Size for Catalysis

“…Ex situ prepared stabilized colloidal Pd (6,(134)(135)(136)(137) and Ru (138) nanoparticles have gained considerable attention due to their high activity and recyclability. Pd equidimensional nanoparticles of mean sizes from 1.7 to 3.7 nm stabilized by PVP were used as a catalytic probe to study structure sensitivity of Heck coupling of p-bromobenzaldehyde with butyl acrylate (25).…”

Synthesis of Highly Functionalized Fluorinated Porphyrins

“…These fluorinated macromolecules can be utilized, for example, as surfactants in biphasic systems [2], phase transfer catalysts [3], and nanoreactors [4]. In the field of material science they have been used as electron transport materials for organic lightemitting diodes [5], materials for non-linear optic [6] and, in the field of biomedicinal chemistry, as drug delivery systems [7].…”

“…The mixture was cooled to -78 °C and LiAlH 4 (1 M solution in diethyl ether, 9 mg, 237 µmol) was slowly added. Then, the cooling bath was removed and the mixture was stirred at laboratory temperature for 1 h. The reaction was quenched with MeOH (2 mL), diluted with water (50 mL) and mixture was extracted with diethyl ether (3×50 mL).…”