Palladium complexes supported on hybrid organic-inorganic zirconium phosphite: selectivity in the Heck reaction

Use of a new hydrophilic phosphine: DPPPA. Rapid and convenient Heck reaction in aqueous medium under microwave irradiation

A new water soluble phosphine-ligand: diphenylphosphinyl) phenylphosphonic acid (DPPPA) was used in Heck reaction. The Heck reaction is efficiently and rapidly achieved by a palladium-catalysed reaction in water performed in a Teflon autoclave under microwave irradiation with a commercial microwave oven. The log P was used for correlating the solubility of the aryl iodide in water with the observed yield.

Rapid and efficient palladium catalysed reduction of aryl halides by triethylsilane under microwave irradiation

Triethylsilane in presence of catalytic amount of palladium chloride is an efficient and selective system for reductive dehalogenation of aryl halides under microwave irradiation.

Pd Catalysis on Dendronized Solid Support: Generation Effects and the Influence of the Backbone Structure

Recent studies revealed that catalysts, prepared on dendronized support, frequently exhibit enhanced activity and selectivity as compared to their non-dendronized analogues. Regretfully, in early studies of the supported dendritic catalysis, no particular attention was paid to the coordinative nature of the dendritic backbone. In this study, we functionalized Wang polystyrene support with three types of dendritic templates: poly(aril benzyl ether), poly(aryl benzyl thioether), and poly(aryl benzyl amine). These dendronized resins were further decorated with phosphine ligands on the periphery and complexed with a Pd(0) catalytic precursor. The catalysis of the Heck and Suzuki reactions of bromobenzene with the first to third generation supported dendritic catalysts was examined and compared to that of the non-dendritic analogues. All of the examined reactions revealed a positive dendritic effect, reflected in up to 5-fold increase in yield, in the most prominent case. The reasons for the observed effect are the proximity of the ligating sites translated into reduced cross-linking and, probably, the increased distance of the catalyst from the polymer matrix. We proved, however, that the latter could not be achieved with a linear spacer. Although the Suzuki reaction was rather insensitive to the backbone structure, the Heck reaction catalysis at 80 degrees C exhibited substantial sensitivity to the nature of the dendritic backbone, with the polyether structure demonstrating the best outcome. This is the first demonstration of the influence of the coordinative ability of the backbone on the activity of a supported dendritic catalyst.

Remarkable dendritic effect in the polymer-supported catalysis of the Heck arylation of olefins

[reaction: see text] Phosphine-palladium complexes, immobilized on polystyrene, demonstrated a remarkable increase in catalytic activity and selectivity in the Heck reaction upon the introduction of a dendritic spacer between the support and phosphine. For some reactions an up to 5-fold increase in yield is observed.