Co3O4−CeO2 Nanocomposites for Low-Temperature CO Oxidation

In an effort to combine the favorable catalytic properties of Co₃O₄ and CeO₂, nanocomposites with different phase distribution and Co₃O₄ loading were prepared and employed for CO oxidation. Synthesizing Co₃O₄-modified CeO₂ via three different sol-gel based routes, each with 10.4 wt % Co₃O₄ loading, yielded three different nanocomposite morphologies: CeO₂-supported Co₃O₄ layers, intermixed oxides, and homogeneously dispersed Co. The reactivity of the resulting surface oxygen species towards CO were examined by temperature programmed reduction (CO-TPR) and flow reactor kinetic tests. The first morphology exhibited the best performance due to its active Co₃O₄ surface layer, reducing the light-off temperature of CeO₂ by about 200 °C. In contrast, intermixed oxides and Co-doped CeO₂ suffered from lower dispersion and organic residues, respectively. The performance of Co₃O₄-CeO₂ nanocomposites was optimized by varying the Co₃O₄ loading, characterized by X-ray diffraction (XRD) and N₂ sorption (BET). The 16–65 wt % Co₃O₄−CeO₂ catalysts approached the conversion of 1 wt % Pt/CeO₂, rendering them interesting candidates for low-temperature CO oxidation.     

Synthesis and Cytotoxic Activity of 1‐{3‐[1‐(5‐Organylsilylfuran‐2‐yl)silinan‐1‐yl]propyl}amines and Some Trimethylgermyl Analogues

New highly cytotoxic 1‐{3‐[1‐(5‐organylsilyl‐furan‐2‐yl)silinan‐1‐yl]propyl}amines and some trimethylgermyl analogues (IC₅₀ 1–7 μg mL^?1) have been synthesized by a hydrosilylation reaction of aliphatic and heterocyclic N‐allylamines in the presence of Speier’s catalyst. The effects of the silacycle, the element‐organic substituent in position 5 of the furan ring, and the structure of the amine on the cytotoxicity of the new compounds have been studied.     

Pricing caps with HJM models: The benefits of humped volatility

In this paper we compare different multifactor HJM models with humped volatility structures, to each other and to models with strictly decreasing volatility. All the models are estimated on Euribor and swap rates panel data maximizing the quasi-likelihood function obtained from the Kalman filter. We develop the analysis in two steps: first we study the in-sample properties of the estimated models, then we test the pricing performance on caps. We find the humped volatility specification to greatly improve the model estimation and to provide sufficiently accurate cap prices, although the models has been calibrated on interest rates data and not on cap prices. Moreover, we find the two-factor humped volatility model to outperform the three-factor models in pricing caps.     

Synthesis and conversions of 2-acetyl-5-methyl-4-nitrofuran. Isomerization and beckman rearrangement of the oxime

2-Acetyl-5-methyl-4-nitrofuran and 3,5-dinitro--methylfuran were obtained by the reaction of 70% nitric acid with 2-acetyl-5-methylfuran, its oxime and semicarbazone in concentrated H₂SO₄. -Bromonitro ketone and a series of 5-methyl-4-nitro-2-furyl-substituted azaheterocyclic compounds based on it were obtained.Latvian Institute of Organic Synthesis, Riga LV-1006; e-mail: elmira@osi.lanet.lv. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1619–1626, December, 1999.     

Silyl Modification of Biologically Active Compounds. 7. Synthesis, Structure, Physicochemical and Biological Properties of Some Silicon-containing “3+1” Oxorhenium(V) Complexes

With the aim of studying the structure-physicochemical properties-biological activity relation, we have synthesized a series of organosilicon neutral oxorhenium(V) complexes with mixed ligands and we have determined their lipophilicity. X-ray diffraction has been used to establish the molecular structure of (3-triphenylsiloxypropanethiolato)(3-thiapentane-1,5-dithiolato)oxorhenium(V), (2-trimethylsiloxy- and 2-hydroxyethanethiolato)[3-(N-methyl)azapentane-1,5-dithiolato]oxorhenium(V). We have studied the neurotropic properties and acute toxicity of the synthesized complexes in vivo and their dependence on the nature of the monodentate and tridentate ligands. We have established that all the studied compounds have pronounced sedative action (they prolong the life of mice under hypoxia conditions, they are phenamine antagonists, they exhibit anticonvulsive action and prevent retrograde amnesia).     

Synthesis of 2-(pyridylazo)-2-furyl-and 2-(pyridylazo)-2-thienylmethines and other heterocyclic Schiff bases in the presence of molecular sieves

The reactions of 2-furaldehyde, 2-thiophenecarbaldehyde, and their 5-methyl derivatives with 2-aminopyridines and some other amines in the presence of molecular sieves as a dehydrating agent and acid catalyst have been studied. A series of new heterocyclic azomethines was synthesized. Proposals were made for the mechanism of the condensation involving 2-aminopyridines and the structure of the intermediates in these processes.Latvian Institute of Organic Synthesis, Riga LV-1006, Latvia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 890–897, July, 2000.     

Synthesis and Structure of Some 2-Trifluoromethyl-substituted Hetarylmethylidene(or propylidene)anilines

The reaction of furan, thiophene, pyridine, and also furylacryloyl aldehydes with 2-trifluoromethylanilines has been studied in the presence of molecular sieves and a series of new heterocyclic aldimines has been synthesized. The molecular and crystalline structure of some of them were determined by X-ray structural analysis.     

Diastereoselective addition of trimethylsilyl cyanide to chiral O‐, S‐ and N‐heterocyclic aldimines

Systematic investigation of asymmetric trimethylsilylcyanation of heterocyclic azomethines has been realized. The addition of trimethylsilyl cyanide to optically active furan, thiophene and pyridine aldimines, derived from (R)‐ and (S)‐1‐phenylethylamine, was studied in the presence of Lewis acids, and a series of the corresponding α‐amino nitriles was obtained in fair to good yields (up to 91%). Unsaturated nitriles were also formed from pyridine imines. The sense of asymmetric induction and the degree of diastereoselectivity in the synthesis of α‐amino nitriles were determined by means of ¹H NMR. The stereochemical outcome is a result of the same sense of asymmetric induction: Re face attack to the (S)‐imines and Si face addition to the (R)‐imines took place. The (R,R)‐ (up to 81%) or (S,S)‐ (up to 87%) α‐amino nitriles predominated in the products obtained from the all furan, thiophene and pyridine (R)‐ or (S)‐imines respectively. Copyright © 2002 John Wiley & Sons, Ltd.