Routes to trans-Chrysanthemic Acid. III. Syntheses from (+)-Limonene and α-Terpineol

Conversion of limonene to cis-homocaronic acid and α-terpineol to Julia's bicyclic ketoxime has been achieved, the acid and the oxime are known precursors of trans-chrysanthemic acid.     

A note to the article “polarographic reduction of germanium” by A.K. Dasgupta and C.K.N. Nair

The nature of the two reduction waves of tetravalent germanium in ammonia-ammonium chloride buffer is described. Contrary to the statement of dasgup'ta and NAIR1 only the height of the first diffusion current should be used for analytical purposes. The second wave corresponds to a catalytic hydrogen evolution. The use of cthylenediaminetetra-acetic acid of pH 6–8 for the analysis of germanium is preferable².     

Structure and energetics of β-diketonates. XVI. Molecular structure and vibrational spectrum of zinc acetylacetonate according to gas-phase electron diffraction and quantum-chemical calculations

The molecular structure of zinc acetylacetonate was studied in a simultaneous electron diffraction and mass spectrometric experiment at 376(7) K and by quantum-chemical calculations. The Zn(acac)₂ molecule has a structure of D _2d symmetry with the chelate rings lying in mutually perpendicular planes. The main geometrical parameters of the molecule are r _h1(Zn-O) = 1.942(4) Å, r _h1(C-O) = 1.279(3) Å, r _h1(C-C_r) = 1.398(3) Å, r _h1(C-C _m ) = 1.504(5) Å, ∠(O-Zn-O) = 93.2(7)°, ∠(Zn-O-C) = 125.9(7)°, ∠(C-C_r-C) = 125.8(14)°, ∠(O-C-C _m ) = 115.2(9)°. The effective rotation angle of methyl groups is close to 30°, which is indicative of the free rotation of these groups. The vibration frequencies were obtained by quantumchemical calculations, and the IR spectrum of the Zn(acac)₂ molecule was interpreted.     

Preparation and Reactions of Thiazole-fused 3-Sulfolenes. Useful Precursors to o-Dimethylene Thiazoles

Thiazole-fused 3-sulfolenes 6 and 7 have been efficiently prepared from 4-bromo-3-sulfolanone 5 in one step. These 3-sulfolenes react as synthetic equivalents to o-dimethylene thiazoles.     

The Semi-ideal Solution Theory. 4. Applications to the Densities and Electrical Conductivities of Mixed Electrolyte and Nonelectrolyte Solutions

Densities and electrical conductivities were measured for the ternary systems NaCl–mannitol(C₆H₁₄O₆)–H₂O, KCl–glycine(NH₂CH₂COOH)–H₂O, KCl–mannitol–H₂O, and NaBr–mannitol–H₂O at 298.15 K. Densities of the binary systems KCl–H₂O, NaBr–H₂O, glycine–H₂O and conductivities of the binary system NaBr–H₂O at 298.15 K were also measured. The measured densities were used to check the predictions of the semi-ideal solution theory. A new approach for predicting the conductivity of ternary electrolyte−nonelectrolyte mixture solutions in terms of the properties of their binary solutions of equal water activity is presented and compared with the measured values. The results show that the semi-ideal solution theory can provide good predictions for the densities and conductivities of the tested ternary electrolyte−nonelectrolyte solutions from the properties of their binary subsystems.     

SUBJECT INDEX to Vol.16,2005

Analytical Chemistry A model-based phenomenological investigation of char combustion kinetics through thermogravimetry.….....Q. CHEN, R. HE, Z. G. LIANG, X. C. XU, C. H. CHEN 393 A Multiwall carbon nanotube-chitosan modified electrode for selective detection of dopamine in the presence of ascorbic acid……….……………….................………. …………………………………………..L. Y. JIANG, C. Y. LIU, L. P. JIANG, G. H. LU 229 A new approach for removal of nitrogen oxides …     

AUTHOR INDEX to Vol.16,2005

AI X. P. 947 AN B. L. 1405 AN D. G. 212 AN L. K. 7 AN L. K. 49 AN L. K. 1451 AN L. K. 1581 AN Y. 681 ANDO M. 736 AO L. 1189 BAI H. 11 BAI H. 457 BAI H. 997 BAI H. 1189 BAI S. Y. 1158 BAI X. L. 975 BAI X. Z. 846 BAI Y. F. 651 BAO Y. D. 49 BAO Z. Y. 1297 BAUDOIN O. 1279 BERG D. J. 4 BIAN Z. P. 1625 BU X. Z. 7 BU X. Z. 1451 BU X. Z. 1581 CAI B. 215 CAI B. 471 CAI C. 812 CAI C. 1313 CAI G. P. 405 CAI J. B. 1503 CAI J. C. 465 CAI J. C. 127…     

Coupling of Methanol and Isobutanol to Ethers over γ-Alumina Catalyst. Kinetic Studies

The kinetic of methanol (MeOH) and isobutanol (iBuOH) coupling to ethers has been studied. Catalytic tests were carried out in the gas phase in a fixed-bed flow microreactor, in the temperature range of 463-533 K, under atmospheric pressure, using -Al₂O₃ as the catalyst. The quasi-homogeneous model for the process was assumed. The reaction rates were described by simple kinetics.     

A study of the structure and energy of β-diketonates. XVIII. Molecular structure of chromium and cobalt tris-acetylacetonates according to quantum chemical calculations and gas electron diffraction

The molecular structure of chromium and cobalt tris-acetylacetonates is studied by the synchronous electron diffraction and mass spectrometric experiment and quantum chemically. It is found that molecules have the D ₃ symmetry with internuclear distances r _h1(Cr-O) = 1.960(4) Å r _h1(Co-O) = 1.893(4) Å. Quantum chemical calculations by the DFT methods with different basis sets yield a structure well consistent with that found in the experiment. Changes in the structural parameters of chromium and cobalt β-diketonate complexes whose ligands differ in ?CH₃, ?C(CH₃)₃, ?CF₃ substituents are considered.     

Ring-closing metathesis and palladium-catalyzed formate reduction to 3-methyleneoxepanes. Formal synthesis of (−)-zoapatanol

A sequence of ring-closing metathesis and palladium-catalyzed formate reduction was developed for preparing O-heterocycles with an exocyclic olefin and applied to the asymmetric synthesis of zoapatanol. The key vicinal stereocenters in zoapatanol were constructed from the l-malic acid-derived lactone by successive chelation-controlled addition of alkyl groups. The O-allylations to prepare the dienes for RCM were achieved with the tertiary alcohols bearing internal olefins. The ring opening of oxepane, a new reaction pathway for the Pd-formate reduction, is also reported.     

Wine,Polyphenols, and Mediterranean Diets. What Else Is There to Say?

A considerable amount of literature has been published claiming the cardiovascular benefits of moderate (red) wine drinking, which has been considered a distinguishing trait of the Mediterranean diet. Indeed, red wine contains relevant amounts of polyphenols, for which evidence of their biological activity and positive health effects are abundant; however, it is also well-known that alcohol, even at a low level of intake, may have severe consequences for health. Among others, it is directly related to a number of non-communicable diseases, like liver cirrhosis or diverse types of cancer. The IARC classifies alcohol as a Group 1 carcinogen, causally associated with the development of cancers of the upper digestive tract and liver, and, with sufficient evidence, can be positively associated with colorectum and female breast cancer. In these circumstances, it is tricky, if not irresponsible, to spread any message on the benefits of moderate wine drinking, about which no actual consensus exists. It should be further considered that other hallmarks of the Mediterranean diet are the richness in virgin olive oil, fruits, grains, and vegetables, which are also good sources of polyphenols and other phytochemicals, and lack the risks of wine. All of these aspects are reviewed in this article.     

The Reaction of α-Amino-Substituted Diphenylphosphine Oxides with Elemental Sulfur and Selenium. A New Route to Thio- and Selenoamides

Abstract

Lithiated α-amino-substituted diphenylphosphine oxides 1 showed an interesting reactivity towards sulfur and selenium, leading to the formation of thioamides 2 and selenoamides 3, which could be isolated in good yields. Two equivalents of the chalcogene were found to be needed for complete conversion of the phosphine oxide anions. In the case of sulfur, diphenylphosphinothioic acid 4 was isolated as a side product, thus explaining the stoichiometry of the reaction (Scheme 1).     

N. S. Kurnakov’s contribution to coordination chemistry

N.S. Kurnakov’s most important works in coordination chemistry are overviewed. Special attention is given to Kurnakov’s dissertation “On Complex Metal Bases,” to his understanding of the structure of coordination compounds, to the mutual effects of ligands, and to the key ideas in coordination chemistry developed by Chugaev and Chernyaev’s school. Kurnakov’s role in the foundation of the Soviet platinum industry is pointed out.     

Kinetics of the β-picoline oxidation to nicotinic acid over vanadia-titania catalyst. 2. Effect of dioxygen and β-picoline

The effect of the dioxygen and β-picoline concentrations on the oxidation of β-picoline to nicotinic acid was studied at 270°C over a 20% V₂O₅-80% TiO₂ (wt. %) catalyst. The study was performed in a differential reactor at constant concentrations of water and nicotinic acid. A considerable excess of dioxygen was shown to be necessary for the formation of nicotinic acid. It was found that the rates of β-picoline transformation into nicotinic acid, pyridine-3-carbaldehyde, pyridine-3-nitrile, pyridine and carbon oxides as well as selectivities to products and the catalyst state depend strongly on the ratio of dioxygen to β-picoline concentrations. The minimum admissible ratio of these concentrations under industrial conditions was determined.     

“Remote” dianions-I. Utility of 4-phenylsulfonylbutanoic acid in the mild conversion of aldehydes and ketones to lactones.

Ketones and aldehydes are converted to lactones in high yield by stepwise treatment with the dianion of 4-phenylsulfonylbutanoic acid and trifluoroacetic anhydride.