α-Methoxy Ketones by the Reaction of Trimethylsilyl Enol Ethers with Lead Tftraacetate in Methanol

Trimethylsily1 enol ethers of acetophenone, 2-acetylthiophene and 2-acetylfuran react with lead tetraacetate in methanol at room temperature to give the α-methoxy ketones in good yields.     

An Improved Synthesis of Ethyl Azodicarboxylate and 1,2,4-Triazoline-3,5-Diones Using Hypervalent Iodine Oxidation

ARSTRACT: Hypervalent iodine oxidstion of 1,2-dicarhethoxy hydrazine (1) and 4-substituted urazoles (3) using iodobenzene diacetate or pentafluoroiodobenzene bis-trifluoroacetate in CH₂Cl₂ at room temperature proceeds smoothly to yield ethyl azodicarboxylate (2) and 4-substituted 1,2,4-triazoline-3,5-diones (4) in excellent yields.     

Synthesis of ent-kaurane diterpene monoglycosides

Synthesis of two ent-kaurane diterpene glycosides, steviol 19-O-β-D-glucopyranosiduronic acid (steviol glucuronide, 5), and 13-hydroxy ent-kaur-16-en-19-oic acid-β-D-glucopyranosyl ester (7) has been achieved from a common starting material, steviol, using phase transfer catalyst. Also, synthesis of an additional 17-nor-ent-kaurane glycoside, namely 13-methyl-16-oxo-17-nor-ent-kauran-19-oic acid-β-D-glucopyranosyl ester (10) was performed using the starting material isosteviol and similar synthetic methodology. Synthesis of all three steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR as well as mass spectral (MS) data.     

Separation of aromatic solvents from oil refinery reformates by a newly designed ionic liquid using gas chromatography with flame ionization detection

The aim of this study was to determine whether the new ionic liquid, N,N‐dimethyl‐2‐oxopyrrolidonium iodide, synthesized in our laboratory is a suitable solvent for the separation of aromatic components benzene, toluene, ethylbenzene, and xylenes from petroleum mixtures (reformates) in liquid–liquid extraction. In pursuance of the above aim, a method to extract all components of a mixture, containing four aromatic components simultaneously, was developed. A new ionic liquid and a previously used liquid were compared for their extraction abilities. These ionic liquids were, respectively, N,N‐dimethyl‐2‐oxopyrrolidinium iodide and 1‐ethyl‐3‐methyl imidazolium ethyl sulfate. The concentrations of each benzene, toluene, ethylbenzene, and xylenes component in the extract and raffinate phases were measured by gas chromatography with flame ionization detection as volume percent to determine the extraction ability of the ionic liquids. The results obtained for both the reformate samples and model mixtures indicated that the new ionic liquid was effective as an extracting solvent for the recovery of aromatic components from reformates. Also the analysis results, using gas chromatography with flame ionization detection, for the reformate samples were as good as the results obtained by a local oil refinery. The extraction results also show that the developed method is very suitable for the separation and analysis of aromatic components in reformates.     

Steric effects in the hypervalent iodine oxidation of ketones

Oxidation of 3-cholestanone (1) with C₆H₅I(OAc)₂ or o-OIC₆H₄COOH or C₆H₅IO₂ in KOH/MeOH yields 2 α-carbomethoxy-A-norcholestane (2). This result is interpreted on mechanistic grounds and compared with the course of the reaction with other sterically hindered ketones such as friedelin, 3-keto, 12-keto, 17-keto steroids, and 2,2,6,6-tetramethyl-4-piperidone.     

Electrochemical behaviour of zinc in alkaline solutions

The cathodic and anodic polarization of zinc in different concentrations of alkaline solutions has been studied under constant-current conditions. The changes of zinc electrode-potential with reference to a Hg/HgO/KOH system have been measured both in KOH and zincate solutions using a “Luggin” capillary and a specially designed cell, current being drawn from an electronic current stabilizer. Time-potential curves have been plotted and it is found that the anodic zinc passivates at a certain stage showing a sudden rise in potential by as much as 3–4 volts. Before the passivation, the main electrode reaction is the formation of Zn⁺⁺, while after the passivation it changes to gas evolution. No definite relationship as previously suggested by Muller, between the current density and the passivation time was found, perhaps due to migration and non-linear diffusion effects and other reasons discussed in the paper. It has been found that the behaviour of zinc differs in concentrated alkaline solutions (i.e., 0·5 N to 5 N) from that in dilute solutions (0·2 N to 0·01 N), in which case the open circuit rest-potential of zinc is indefinite and may vary by as much as 500–600 mV., while the maximum passivation jump in potential is about 2 volts only. Also the passivation and the decay of current on breaking the circuit are found to be slower than in the case of concentrated solutions. Colour changes of the zinc electrode, during the polarization, are also briefly described and discussed.