A rapid and effective synthesis of propylene carbonate using a supercritical CO2-ionic liquid system

The synthesis of propylene carbonate from propylene oxide and carbon dioxide under supercritical conditions in the presence of 1-octyl-3-methylimidazolium tetrafluoroborate was achieved in nearly 100% yield and 100% selectivity within 5 minutes, whose TOF value is 77 times larger than those so far reported.     

Determination of aluminum oxide in and on high-purity aluminum by a phenol dissolution method

A simple rapid determination of aluminum oxide in aluminum is described. Aluminum reacts with phenol at 180°C forming aluminum phenoxide but aluminum oxide does not. After the reaction, the aluminum oxide is filtered off and brought into aqueous solution by fusion with potassium hydrogensulfate for determination by atomic absorption spectrometry or by the 8-quinolinol spectrophotometric method. The reaction between aluminum and phenol is stoichiometric. The procedure is applicable to the determination of aluminum oxide in commercial aluminum metals of various forms. The method is relatively rapid and appears to be superior to the conventional bromine—methanol method.     

Sodium borosilicate glasses prepared by the sol-gel process

A sodium borosilicate gel of composition 80SiO₂·15B₂O₃·5Na₂O (wt%) was prepared from tetraethyl orthosilicate, trimethyl borate, sodium methylate, H₂O, and HCl as the catalyst. Variation of specific surface area and porosity as a function of heating temperature indicated that closed pores were opened at temperatures lower than 400°C and collapsed above 450°C. From TG and DTA curves, about 19% Si and B atoms are evaluated to have −OH bonds. X-ray diffraction patterns indicated crystallization of low-cristobalite out of the gel when it was heated at 700°C for 5 h, showing a difference from a melt-quenched glass of the same composition.     

One-Pot Preparation of 1-Substituted Imidazole-2-thione from Isothiocyanate and Amino Acetal

Isothiocyanates were treated with amino acetal and conc. HCl (0.5 eq.) successively in one-pot to afford 1-substituted imidazole-2-thiones in good yields.     

Amdigenol A,a long carbon-backbone polyol compound,produced by the marine dinoflagellate Amphidinium sp

A polyol compound, amdigenol A, was isolated from the dinoflagellate Amphidinium sp. that adhered to the surface of the marine alga Digenea simplex. A structural elucidation was performed by 2D-NMR spectroscopy, degradation with a second generation Hoveyda–Grubbs catalyst and ESI-CID-MS/MS analyses. Amdigenol A consists of a C₉₈-linear carbon backbone including two core structures of amphidinol analogs and is likely formed linearly by two amphidinol analogs.     

Microwave-assisted direct transformation of amines to ketones using water as an oxygen source

Retro-reductive aminations, direct transformations of amines to ketones, were catalyzed by Pd/C in water under microwave irradiation.     

The effect of various substances on the suppression of the bitterness of quinine-human gustatory sensation,binding, and taste sensor studies

The purpose of this study was to quantify the degree of suppression of the perceived bitterness of quinine by various substances and to examine the mechanism of bitterness suppression. The following compounds were tested for their ability to suppress bitterness: sucrose, a natural sweetener; aspartame, a noncaloric sweetener; sodium chloride (NaCl) as the electrolyte; phosphatidic acid, a commercial bitterness suppression agent; and tannic acid, a component of green tea. These substances were examined in a gustatory sensation test in human volunteers, a binding study, and using an artificial taste sensor. Sucrose, aspartame, and NaCl were effective in suppressing bitterness, although at comparatively high concentrations. An almost 80% inhibition of bitterness (calculated as concentration %) of a 0.1 mM quinine hydrochloride solution required 800 mM of sucrose, 8 mM of aspartame, and 300 mM NaCl. Similar levels of bitterness inhibition by phosphatidic acid and tannic acid (81.7, 61.0%, respectively) were obtained at much lower concentrations (1.0 (w/v)% for phosphatidic acid and 0.05 (w/v)% for tannic acid). The mechanism of the bitterness-depressing effect of phosphatidic acid and tannic acid was investigated in terms of adsorption and masking at the receptor site. With phosphatidic acid, 36.1% of the bitterness-depressing effect was found to be due to adsorption, while 45.6% was due to suppression at the receptor site. In the case of 0.05 (w/v)% tannic acid, the total bitterness-masking effect was 61.0%. The contribution of the adsorption effect was about 27.5% while the residual masking effect at the receptor site was almost 33%. Further addition of tannic acid (0.15 (w/v)%), however, increased the bitterness score of quinine, which probably represents an effect of the astringency of tannic acid itself. Finally, an artificial taste sensor was used to evaluate or predict the bitterness-depressing effect. The sensor output profile was shown to reflect the depressant effect at the receptor site rather well. Therefore, the taste sensor is potentially useful for predicting the effectiveness of bitterness-depressant substances.     

Dioxygen activation and substrate oxygenation by a p-nitrothiophenolatonickel complex: unique effects of an acetonitrile solvent and the p-nitro group of the ligand

The nickel(II) complex [Ni(Tp(Me2)) (SC(6)H(4)NO(2))] [1a; Tp(Me2) = hydrotris(3,5-dimethylpyrazol-1-yl)borate] reacts with O(2) to form the ligand oxygenation product ArSO(2)(-) in MeCN, and also 1a catalyzes the oxygenation of external substrates such as triphenylphosphine. The reactivity may correlate to the unique quinoid-like resonance structure of the thiophenolate ligand. The structure is stabilized by a p-nitro group and induced by coordination of MeCN.     

Total synthesis and absolute stereochemistry of (+)-batzellaside B and its C8-epimer, a new class of piperidine alkaloids from the sponge Batzella sp.

The first total synthesis of (+)-batzellaside B and its C8-epimer was completed from a known l-arabinose-derived tribenzyl ether in 22 steps with overall yields of 3.9% and 5.4%, respectively. The absolute configuration of (+)-batzellaside B was unambiguously determined to be 1S,3S,4S,5R,8S by the Mosher analysis of a synthetic intermediate prepared through a separate route.