Hydrogenation of m-xylene catalyzed by a silica-supported polysilazane–platinum complex

A new kind of inorganic polymer, silica-supported polysilazane (Si–N), and its platinum complex (Si–N–Pt) were prepared and characterized by X-ray photoelectron spectroscopy. It was found that Si–N–Pt can catalyze hydrogenation of m-xylene under mild conditions (30–50°C, 1 atm). The products of the reaction were cis- and trans-1,3-dimethylcyclohexane. The formation of trans-1,3-dimethylcyclohexane may be adequately explained according to the “roll-over” model. The stereoselectivity was influenced by temperature and catalyst concentration, the proportion of the cis isomer decreasing with an increase in each of the two factors. The effects of other reaction parameters, such as the N/Pt mole ratio in the complex, solvents and reaction time, etc., on the hydrogenation of m-xylene were also studied. The Si–N–Pt catalyst is very stable in reaction and turnover numbers amount to 520 in 70 hr.     

Hydrogenation of aldehydes and ketones catalyzed by a polysulfosiloxane–platinum complex

An acidic inorganic polymer, polysulfosiloxane, has been prepared and used as ligand for preparing a polysulfosiloxane–platinum complex. It has been found that such a complex could catalyze the hydrogenation of aldehydes and ketones to alcohols, giving as much as 100% yield at room temperature and under atmospheric pressure. Temperature, S/Pt molar ratio in the complex and solvents greatly influenced the reaction. This complex was very stable and could be used several times without any change in catalytic activity.     

Hydrogenation of ketones and olefins via hydrogen transfer catalyzed by rhodium and iridium phosphine complexes

The reduction of ketones and olefins by hydrogen transfer from isopropanol is catalyzed by tertiary phosphine complexes of rhodium and iridium. The influence of the nature of the ligands and of the reaction conditions on the catalytic activity has been investigated. The reduction of the carbonyl group in the presence of olefins is also reported.     

Hydrogenation of nitroarenes catalyzed by a dipalladium complex

A dipalladium complex [Pd₂( L )Cl₂](PF₆)₂ ( 2 ), via the substitution of (PhCN)₂PdCl₂ with 5‐phenyl‐2,8‐bis(6′‐bipyridinyl)‐1,9,10‐anthyridine ( L ) followed by the anion exchange, was found to be a good pre‐catalyst for the reduction of nitroarenes to yield the corresponding anilines under atmospheric pressure of hydrogen in methanol. This method provides a straightforward access to a diverse array of functionalized anilines, exhibiting a possible application in synthetic chemistry. The catalytic activity of this complex is enhanced by the di‐metallic system via the synergistic effect.     

Highly enantioselective carbonyl-ene reactions catalyzed by a hindered silyl-salen-cobalt complex

We report here the enantioselective carbonyl-ene reactions of various 1,1-disubstituted and trisubstituted alkenes with ethyl glyoxylate. The reactions are catalyzed by a new Co-salen complex, in which bulky triisobutylsilyl (TIBS) substituents occupy the positions ortho to the phenolic oxygens. This complex catalyzes the reactions under nearly ideal conditions - at room temperature and using catalyst loadings as low as 0.1 mol % - and provides the chiral, homoallylic alcohol products in excellent yields, enantioselectivities, and diastereoselectivities.     

Hydrogenation of nitroarenes on silica-supported copper catalyst

A 9% Cu/SiO₂ catalyst prepared by the deposition– precipitation technique was active in the hydrogenation of substituted nitrobenzenes at 170 °C and 13 atm H₂ in a batch reactor. Nitro groups were selectively reduced to NH₂ groups except for the case of 5-bromo-1,3-dinitrobenzene. The selectivity of the overall process is somewhat suppressed by inevitable formation of azo compounds and traces of tars due to the reactions of the obtained amines with nitroso intermediates.     

Aquametric microdetermination of sterically hindered ketones

Conclusions The previously developed aquametric micromethod for determining carbonyl compounds also gives reliable results when most of the sterically hindered ketones studied by us are analyzed. The determination error is ±0.3%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 942–944, April, 1972.     

Enantioselective cyanosilylation of ketones catalyzed by a chiral oxazaborolidinium ion

The chiral oxazaborolidinium salt 1 (X = TfO) is an excellent catalyst for the cyanosilylation of methyl ketones promoted by trimethylsilyl cyanide and diphenylmethyl phosphine oxide as co-reactants (to generate Ph(2)MePOTMS(N=C:) as a reactive intermediate). The face selectivity of this reaction parallels that previously observed for the corresponding reaction of aldehydes. A unifying and rational mechanistic explanation is provided for these enantioselective reactions. Evidence is presented to support the importance of alpha-C-H...O hydrogen bonding, pi,pi-interaction of the complexed ketonic carbonyl with the mexyl group of 1, and an early transition state for high enantioselectivity. The cyanosilylation reaction described herein provides access to many useful chiral compounds.     

水溶性Rh-BISBIS配合物对阿维菌素催化加氢的研究

The hydrogenation of avermectin catalyzed by [RhCl(COD)]_2-BISBIS[COD:1,5-cyclooctadiene,BISBIS:sulfonated 1,1'-bis(diphenylphosphino Methyl-2,2'-biphenyl)] in situ in aquenous/organic two-phase system was studied.The influence of various parameters,such as the surfactant concentration,the molar ratio of rhodium to phosphine,the reaction temperature and pressure on this hydrogenation were investigated.The results showed that the hydrogenation activities of diphosphine was higher that of monophosphine.     

Oxidation of methanol catalyzed by silica-supported polystannazane–copper complex

Silica-supported polystannazane–copper complex has been prepared and used as a catalyst for the oxidation of methanol. The results showed that the catalyst could catalyze the oxidation of methanol to formaldehyde at a high yield and selectivity at 30°C and under 1 atm mild conditions. The N/Cu mole ratio in the complex, temperature and the amount of NaOH additive had much influence on the catalytic activity. The complex was stable during the reaction and could be used repeatedly.     

Selective hydrogenation of chloronitrobenzenes catalyzed by palladium complex of silica-supported chitosan

A palladium complex of silica-supported chitosan has been found to catalyze the hydrogenation of p-, m- and o-chloronitrobenzene, and of 4-chloro-1,3-dinitrobenzene to p-, m- and o-chloroaniline, and 4-chloro-3-aminoaniline in 100% yield, respectively, at room temperature and under atmospheric pressure, and the side reaction, dechlorination, has not been observed. This catalyst was very stable, the turnover numbers (p-chloronitrobenzene to p-chloroaniline cycles / palladium atom) reached 9000 in 17 hours.     

Transfer hydrogenation of ketones catalyzed by ruthenium complexes

Oxidation of 1,3,5- and 1,2,4-trimethylbenzenes using heteropoly vanadomolybdate as catalyst in the presence of hydrogen peroxide under homogeneous conditions has been investigated. Phenol formation in the case of 1,2,4-trimethylbenzene and only side chain oxidation in the case 1,3,5-trimethylbenzene were observed. This behavior is explained in terms of the charge densities on different centers of both substrate molecules calculated by the MNDO method.