•The silica-immobilized Pd-phosphine complex catalysts were prepared using a tripodal linker.•The tripodal linker was effective for preventing catalyst leaching for Suzuki coupling.•The capping of residual Si-OH on silica improved catalyst performance for Suzuki coupling.Silica-immobilized palladium phosphine complex catalysts bearing a tripodal linker unit were tested for their ability to facilitate the Suzuki–Miyaura coupling reactions of aryl chlorides. The catalyst containing the tripodal linker with a trimethylsilyl capping group on the residual surface silanol groups displayed better catalytic activities and lower palladium and phosphorus leaching levels than the catalysts bearing a conventional trialkoxy-type linker.

To clarify the effectiveness of a tripodal linker unit (3-bromopropyltris[3-(dimethylisopropoxysilyl)propyl]silane), which can be bound to a silica surface via three independent Si–O–Si bonds, silica-immobilized palladium amine complex catalysts employing the tripodal linker unit were prepared and applied toward the Suzuki–Miyaura coupling reaction. N-Functionalized (N = 3-methylaminopropyl, 3-dimethylaminopropyl, or N,N-dimethylethylenediaminopropyl) silica materials were prepared by grafting the tripodal linker unit onto mesoporous silica followed by treatment with the corresponding amine. A series of silica-immobilized amino-palladium complex catalysts were prepared by reacting N-functionalized silica materials with palladium acetate. A catalyst that included a methylamino ligand and a ligand-to-Pd molar ratio of 6:1 gave the best performance for the reaction between aryl bromides and phenylboronic acid in toluene. Moreover, catalysts containing the tripodal linker showed lower levels of palladium leaching after the reaction and better recyclability compared to catalysts having conventional trialkoxy-type linkers.Graphical abstractHighlights► The silica-immobilized Pd complex catalysts were prepared using a tripodal linker. ► The tripodal linker was effective for preventing Pd leaching for Suzuki coupling. ► The tripodal linker improved catalyst recyclability for Suzuki coupling.

The Pd phosphine complex catalysts immobilized onto polyethylene glycol (PEG)-modified silica were prepared in order to clarify the effect of the PEG modification on the Suzuki–Miyaura coupling reaction in organic solvents. For the reaction of ethyl p-bromobenzoate and phenylboronic acid in the presence of potassium carbonate in toluene, the PEG-modified silica-immobilized Pd catalysts exhibited much higher activities than the catalysts without PEG modification.

Various substituted nitroaromatics were successfully hydrogenated to the corresponding N-aryl hydroxylamines in excellent yields (up to 99%) using supported platinum catalysts such as Pt/SiO2 under a hydrogen atmosphere (1 bar) at room temperature. The key to the fast and highly selective formation of hydroxylamines is the addition of small amounts of amines such as triethylamine and dimethyl sulfoxide; amines promote the conversion of nitroaromatics, while dimethyl sulfoxide inhibits further hydrogenation of hydroxylamines to anilines. The promotive effect depends on which type of amine and primary amine was most effective. The hydrogenation efficiently proceeded in common organic solvents, including isopropanol, diethyl ether, and acetone. This methodology should extend the application range of conventional solid catalysts to fine chemicals synthesis.

The presence of the heterogeneous mesoporous Al-MCM-41 catalyst remarkably accelerated the cyanosilylation of various aldehydes and ketones with trialkylsilyl cyanide, giving the corresponding cyanohydrin silyl ethers in quantitative yields under mild reaction conditions.

The presence of the heterogeneous mesoporous Al-MCM-41 catalyst remarkably accelerated the cyanosilylation of various aldehydes and ketones with trialkylsilyl cyanide, giving the corresponding cyanohydrin silyl ethers in quantitative yields under mild reaction conditions.