One-pot enantioselective formation of eight-membered rings from alkenyl Fischer carbene complexes and ketone enolates

Eight-membered carbocycles with up to five new stereogenic centers are enantioselectively obtained following a one-pot procedure that involves the coupling of three components: an alkenyl Fischer carbene complex, a ketone enolate, and allyl lithium.     

On the biological importance of the hydrogen bond breaking potency of fluorocarbons

Fluorocarbons containing higher halogens have the potency of breaking certain hydrogen bonds in solutions. The relative strength of this potency varies in the series F < Cl < Br < I and the presence of hydrogen atoms in the fluorocarbon increases it. There is a striking parallelism between the hydrogen bond breaking and the anaesthetic potency of these molecules. It is suggested that the breaking of hydrogen bonds is an important step in the mechanism of anaesthesia.     

Über die Möglichkeit der Ausrichtung der Schwärzungskurve

Zusammenfassung Nach Besprechung der bestehenden Möglichkeiten zur geradlinigen Transformation der Schwärzungskurve wird auf Grund der Ergebnisse zahlreicher Messungen eine Gleichung entwickelt, mit deren Hilfe über einen größeren Gradationsbereich eine Skala transformierter Schwärzungswerte aufgestellt wird. Es wird ein Apparat beschrieben, der eine rasche Verwendung dieser Skala gestattet. Die praktische Bedeutung dieser theoretischen Überlegungen wird an den Beispielen der Bestimmung von Bor in Stahl sowie von Silber und Kupfer in reinem Blei beschrieben.     

Stereospecific uncatalyzed alpha-O-glycosylation and alpha-C-glycosidation by means of a new D-Gulal-derived alpha vinyl oxirane

The reaction of alpha vinyl oxirane 5, prepared through a new route to the d-gulal system, with O-nucleophiles (alcohols and di-O-isopropylidene-alpha-d-monosaccharides) and C-nucleophiles (lithium alkyls) affords, in a completely stereoselective way, the corresponding 2-unsaturated alpha O- and C-glycosides having the same configuration as the starting epoxide.     

氢化物发生—分光光度法测定染发剂中的微量铅

本文提出了用铁氰化钾将铅氧化至高价,再用氢化物发生-分光光度法测定铅的一种新方法。该法灵敏度高,简便快速,用于分析染发剂中的铅,取得了较好的效果。     

Oxidation of organophosphorus compounds—IV : Kinetics and mechanism of the oxidation of diarylphosphine oxides by t-butyl hydroperoxide,hydrogen peroxide and p-nitroperoxybenzoic acid in alkaline media

The influence of OH⁻ concentration, in the solvent medium dioxane-water 40:60 at 25·0, on the oxidation rates of diphenylphosphine oxide (DPPO) by t-BuOOH, H₂O₂ and p-nitroperoxybenzoic acid, and of bis-p-tolylphosphine oxide by t-BuOOH has been investigated. For the oxidation of the phosphorus substrates by the hydroperoxides above, the rate law found (R = k₂″[Ar₂PHO] [ROO⁻]) differs from the rate law confirmed to hold for the oxidation of DPPO by peroxyacids in alkaline media, i.e.: R = (k₂″ + k₃[OH−])[Ar₂PHO] [RCO₃⁻]. This is interpreted on the basis of one common reaction mechanism involving formation of an intermediate of similar structure, wherein a change in the rate controlling step is likely to occur on passing from p-O₂N·C₆H₄CO₃⁻ to t-BuOO⁻. In the same solvent medium, pK_a′ values for t-BuOOH and H₂O₂ have been estimated.     

New phosphite-oxazoline ligands for efficient Pd-catalyzed substitution reactions

We have designed and synthesized a new family of readily available highly modular phosphite-oxazoline ligands for the Pd-catalyzed asymmetric allylic substitution reactions. The introduction of a pi-acceptor flexible bulky biphenyl phosphite moiety in the ligand design is highly adventitious in the product outcome. Thus, this ligand series affords excellent reaction rates (TOF's up to >2400 mol.(mol.h)-1) and enantioselectivities (ee's up to >99%) and, at the same time, shows a broad scope for different substrate types.     

Complexation of an acrylic resin by tertiary amines: synthesis and characterisation of new binders for antifouling paints

Antifouling coatings are the most reliable way to prevent biofouling of immersed surfaces. As concerning the high toxicity of organotin paints, the tendency is the development of coatings, which do not present environmental risks. In this work, we prepare binders from modification of acrylic copolymers containing free carboxylic acid groups. Biocides chosen are tertiary ammonium salts; alkyl chain substituents with different length are considered. The chemical modifications of resins are carried out via a single step reaction. Modification extents are monitored through proton nuclear magnetic resonance and thermogravimetric analysis and the modified resins are characterised by Fourier transform infrared spectroscopy. The glass transition temperature of the acrylate systems is assessed by dynamical mechanical analysis (pin point method) and compared with data obtained by differential scanning calorimetry. The erosion and antifouling properties of the binders are followed during an exposure to marine environment by a visual observation.     

Asymmetric Synthesis of α-Substituted-γ-butyrolactone Empolying Prolinol Type of Auxiliaries

Eleven (S)-(-)-bishydrocarbyl-(l-alkanoylpyrrolidin-2_yl)_methanol derivatives of three types were synthesized from L-proline.asymmtncally selective alkylation products were obtained oy LDA treatment and alkylation using methyl 2-bromoethyl ether, and three types of chiral α-Substituted-γ-butyrolactones were obtained by hydrolyzing the alkylation products, with %e.e. beijing up to 89 percent.     

丝氨酸织组膜电极的研究

利用猪肝组织膜配合氨气敏电极,研制了丝氨酸生物催化传感电极。丝氨酸浓度的测定范围为5.1×10~(-5)～3.2×10~(-3)mol/L,检出限为3.1×10~(-5)mol/L。研究和讨论了电极的最佳工作条件,并测定了实验条件下酶催化反应的米氏常数Km。该电极用于合成样品分析,效果满意。