Jiajian Peng

Asymmetric zinc-catalyzed hydrosilylation of ketones and the effect of carboxylate on the enantioselectivity.

Several chiral ligands containing (R,R)-diaminocyclohexane moieties and pyrrole, furan, or benzene have been synthesized. These ligands were tested in enantioselective zinc-catalyzed hydrosilylation reactions; excellent enantioselectivities were obtained when the ligands containing (R,R)-diaminocyclohexane moieties and furan rings were used. For comparison, zinc chloride combined with different potassium carboxylate salts and ligands were also tested for catalytic hydrosilylation reactions.

Hydrosilylation catalysed by a rhodium complex in a supercritical CO2/ionic liquid system

The hydrosilylation of alkenes in a supercritical CO2 (scCO2)/ionic liquid (IL) system was investigated. Rh(PPh3)3Cl exhibited excellent catalytic activity and selectivity. KOtBu was used as an additive, and no hydrogenation by-product (alkane) was detected in the scCO2/IL system. During hydrosilylation in the scCO2/IL system, the reactants were possibly transferred into the IL phase by scCO2, in which the catalyst was dissolved. The products can be flushed with scCO2 after the reaction and the catalyst/IL system reused.

Use of functionalized PEG with 4-aminobenzoic acid stabilized platinum nanoparticles as an efficient catalyst for the hydrosilylation of alkenes

A catalyst containing functionalized polyethylene glycol with 4-aminobenzoic acid (PEG-AMB) stabilized platinum nanoparticles has been synthesized and characterized, and its application in the hydrosilylation of alkenes investigated. It is shown that the functionalized PEG-stabilized Pt nanoparticles form a very efficient catalyst for the hydrosilylation of alkenes. The Pt nanoparticles can be fully immobilized in the PEG-AMB and recycled at least nine times without any obvious loss of catalytic activity.

Rapid Selective Defunctionalization of the Carbonyl Group of α,β-Unsaturated Ketones with Trialkoxylsilane/ZnX2

Abstract Reduction of the carbonyl group of ketones to a methylene unit is widely applied in organic syntheses. In this article, we report that trialkoxylsilane/Zn-based catalyst systems may be applied in the reduction of the carbonyl groups of α,β-unsaturated ketones to methylene units under very mild conditions. In comparison with other Zn-based catalysts, excellent rates and high conversions of α,β-unsaturated ketones to methylene units are obtained using trialkoxylsilane/ZnI2 or ZnCl2. And the same time, the hydrosilylation reaction product could only be detected when using CuI, CuCl, or FeCl3. No reaction could be conducted by using trialkoxylsilane/CoCl2 or NiCl2, in comparison with Zn-based catalysts. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT

Functional Polyethylene Glycol with Carboxyl-supported Platinum as an Efficient Catalysis System for the Hydrosilylation of Alkenes *

Abstract A series of carboxylated long chain polyethylene glycols (abbreviated as PEGCOOH) has been synthesized and used to support chloroplatinic acid. These supported catalysts were then tested for their efficiency in the hydrosilylation of alkenes. The factors affecting their catalytic properties, e.g. relative molecular mass of polyethylene glycol, reaction temperature, platinum content, and type of alkenes, have been studied. It was found that the activity of the platinum catalyst decreased with increasing length of the polyethylene glycol chain, and increased with reaction temperature. Moreover, these catalysts could be reused several times without a noticeable decrease in activity or selectivity. The reaction pathway leading to excellent selectivity for the β-adduct of hydrosilylation of alkenes with triethoxysilane catalyzed by this catalysis system was discussed.

Hydrosilylation Catalyzed with Rh(PPh3)3Cl/Ionic-Liquid–Functionalized SiO2

Ionic liquid–modified silica has been prepared by a “one-pot” reaction of activated silica, 3-chloropropyltriethoxysilane, and alkylimidazole or pyridine. It was found that the catalytic activity and β-adduct selectivity of the supported catalyst Rh(PPh3)3Cl/ionic-liquid–modified-SiO2 for the hydrosilylation reaction of alkenes with triethoxysilane was significantly improved. Furthermore, the catalyst system could be recovered easily.

Rh(PPh3)3Cl/Tetrakis(Dialkylamino)Phosphonium Salts as Thermoregulated and Recyclable Catalytic System for Hydrosilylation Reaction

Abstract Eleven tetrakis(dialkylamino)phosphonium salts have been prepared and were used as “soft” catalyst supports for the hydrosilylation reaction of styrene with triethoxysilane catalyzed by Rh(PPh3)3Cl. Among the Rh(PPh3)3Cl/tetrakis(dialkylamino)phosphonium salts tested, the best catalytic activity and selectivity in favor of the β-adduct were obtained when {[(C4H9)2N]3[(C8H17)2N]P}PF6 was used as the support, and Rh(PPh3)3Cl/ {[(C4H9)2N]3[(C8H17)2N]P}PF6 catalyst system can be reused more than 10 times without noticeable loss of catalytic activity and selectivity. GRAPHICAL ABSTRACT

The catalytic activity of alkali metal alkoxides and titanium alkoxides in the hydrosilylation of unfunctionalized olefins

Abstract The catalytic activities of titanium alkoxides and alkali metal alkoxides for hydrosilylation of unfunctionalized olefins have been studied. Titanium(IV) alkoxides showed excellent catalytic activity, while alkali metal alkoxides have low catalytic activity for the hydrosilylation of olefins. However, by using titanocene dichloride as an additive, alkali metal alkoxides showed also excellent catalytic property for hydrosilylation. In comparison with titanium alkoxides, no α-adduct was obtained by using alkali metal alkoxides/Cp2TiCl2 as catalysts. GRAPHICAL ABSTRACT

Titanium-catalyzed hydrosilylation of olefins: A comparison study on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4 catalyst system

Abstract Hydrosilylation of olefins catalyzed by Cp2TiCl2/Sm (Cp = cyclopentadienyl) under solvent free conditions have been investigated. By using Cp2TiCl2/Sm as catalyst system, β-adducts and hydrogenation products were detected. Hydrosilylation of olefins catalyzed by Cp2TiCl2/LiAlH4 under room temperature has also been studied. The influence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4, respectively, indicated that hydrosilylation of olefins catalyzed with Cp2TiCl2/Sm went through a free radical reaction pathway while a coordination mechanism was applied for Cp2TiCl2/LiAlH4 catalyst system. GRAPHICAL ABSTRACT

N-heterocyclic carbene platinum complexes functionalized with a polyether chain and silyl group: Synthesis and application as a catalyst for hydrosilylation

GRAPHICAL ABSTRACT ABSTRACT The synthesis and characterization of new N-heterocyclic carbene platinum(II) complexes functionalized with a polyether chain and silyl group are described. In addition, their application towards the catalytic hydrosilylation of unsaturated carbon–carbon bonds, including alkenes, alkynes, vinyl ether, and unsaturated esters, is reported. These new complexes exhibit both excellent catalytic activity and selectivity for hydrosilylation. The catalytic system can be recycled >27 times.