Influence of quaternary onium salts,crown ethers and cryptands on olefin epoxidations promoted by HOCl/ClO− in the Presence of Mn(III)-tetrakis(2,6-dichlorophenyl)porphyrin chloride

Reaction rates of alkene epoxidations, promoted by aqueous NaOCl and catalyzed by Mn(III)-tetrakis(2,6-dichlorophenyl)porphyrin chloride1 (P) in the presence of a lipophilic axial ligand (L) (e.g.N-hexylimidazole) and carried out under H₂O/CH₂Cl₂ two phase conditions at 0°C, are strongly enhanced by lowering the pH of the aqueous phase from 12.7 to 9.5. Under these conditions, a further relevant increase in the reaction rates can be achieved by adding phase-transfer catalysts (PT), e.g. quaternary ammonium salt 3, lipophilic crown ether4 or cryptand5, provided that the amount of L is very small (L/P=1 for very reactive alkenes, e.g. cyclooctene, and 10 for poorly reactive ones, e.g. 1-dodecene). In the case of cyclooctene epoxidation, the use of 0.006–0.03 mol. equiv. of PT completes the reaction in 1–10 min., the initial rates being up to 600 turnovers/min. with (2.2.2,C₁₀) cryptand. In the absence of the axial ligand, the quaternary ammonium salt3 and cryptand5 show an inhibitory effect. Such an effect is due to the formation of the poorly reactive Mn(P)CI species, by Cl– extraction to the organic phase. However, dibenzo crown ether 4 does not show this effect. In the presence of 4, and with L/P =1, the 1-dodecene epoxidation reaches 94% in 1 min. The unique behavior of crown ethers can be explained by their ineffectiveness in extracting alkali chlorides, providing a very low concentration of Cl– in the organic phase and thus avoiding the Mn(III)-porphyrin deactivation.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

On triviality of the Kashiwara–Vergne problem for quadratic Lie algebras

We show that the Kashiwara–Vergne (KV) problem for quadratic Lie algebras (that is, Lie algebras admitting an invariant scalar product) reduces to the problem of representing the Campbell–Hausdorff series in the form $\ln (e^x{e}^y)=x+y+[x,a(x,y)]+[y,b(x,y)]$, where $a(x,y)$ and $b(x,y)$ are Lie series in x and y. This observation explains the existence of explicit rational solutions of the quadratic KV problem, whereas constructing an explicit rational solution of the full KV problem would probably require the knowledge of a rational Drinfeld associator. It also gives, in the case of quadratic Lie algebras, a direct proof of the Duflo theorem (implied by the KV problem). To cite this article: A. Alekseev, C. Torossian, C. R. Acad. Sci. Paris, Ser. I 347 (2009).     

Synthesis and Reactivity of bis-Lactamic Compounds

A preparation of bis-lactams is described from α-ketols and bis-cyanamides in the presence of sodium ethoxide at room temperature. One of these compounds leads to an unsaturated derivative by condensation with furfural, or to a saturated analogue via catalytic hydrogenation.     

Nachweis und Bestimmung des Bleis

Ohne Zusammenfassung     

Characterisation of protease activity in extracellular products secreted by Giardia duodenalis trophozoites treated with propolis

Results from our laboratory revealed propolis activity on Giardia trophozoites proliferation. Since therapeutic agents can inhibit the activity of proteases related to relevant biologic and physiologic processes of parasites, this study was undertaken to characterise the proteolytic activity of excretory/secretory products (ESP) of trophozoites treated with propolis. ESP was obtained from culture supernatants of trophozoites exposed to 250 and 500 μg mL(-1) of propolis. ESP were tested in sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the protein profiles and the protease activity was assayed in gelatin-containing gels. Synthetic inhibitors were used to characterise the protease classes. Treated and non-treated ESP showed a similar protein and hydrolysis pattern. A simple pattern of protein composed by five evident bands of approximately 167, 132, 79, 61 and 51 kDa was found, and the zymograms comprised hydrolysis zones distributed from >170 to 23 kDa. No inhibition was seen on protease activity of propolis-treated trophozoites, whose hydrolysis pattern was similar to control. One may conclude that both ESP degraded gelatin and the activity was predominantly due to cysteine proteases. Although propolis had no effect on the proteolytic activity, further studies could identify the active constituents responsible for propolis antigiardial activity and their mechanisms of action.     

Alkylation directe de cetones et d'aldehydes en presence de potasse solide en suspension

Dehydrated solid KOH, suspended in aprotic solvents, is used as a base for ketone and aldehyde alkylation. The best solvent as regards yields and selectivity is DME. The quantity of KOH depends on the carbonyl compound acidity. This method gives as good results as less convenient homogeneous conditions.     

Kontsevich Deformation Quantization and Flat Connections

In Torossian (J Lie Theory 12(2):597–616, 2002), the second author used the Kontsevich deformation quantization technique to define a natural connection ω _n on the compactified configuration spaces [`(C)]_n,0{\overline{C}_{n,0}} of n points on the upper half-plane. Connections ω _n take values in the Lie algebra of derivations of the free Lie algebra with n generators. In this paper, we show that ω _n is flat.