The Enol Lactone Approach to Protected Hydroxy γ-Lactones (5-Hydroxy-dihydro-furan-2-ones)

Oxidation of 5-alkylidene-dihydro-furan-2-ones with dimethyldioxirane and opening of the resulting epoxide furnished γ-alkoxy and α-siloxy protected γ-lactones.     

Efficient Synthesis of α,β-Diamino Acid Derivatives by In(III)-Catalyzed Regioselective Addition of Amines to Aziridines

An efficient catalytic method for the synthesis of α, β-diamino acid derivatives has been developed via regioselective ring opening of aziridines by amines in the presence of indium(III) salt under very mild reaction conditions.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Tween-20: An Efficient Catalyst for One-Pot Synthesis of α-Aminophosphonates in Aqueous Media

Abstract

A green one-pot three-component synthesis has been developed for α-aminophosphonates by condensation of aldehydes, amines, and diethylphosphite by using nonionic surfactant Tween-20 as catalyst in aqueous media. The results showed that this synthetic route for α-aminophosphonates takes just 25–60 min for completion at 60 °C and affords 64%–91% yields depending on the nature of the amine substrates. The major advantages of this novel method are green reaction conditions with water as solvent, simple workup, less reaction times, and high to moderate yields.     

Gold Nanoparticle-based Colorimetric Assay for Determination of Lead(Ⅱ) in Aqueous Media

The authors presented a simple colorimetric assay for the detection of toxic heavy metal lead(Ⅱ) ion(Pb2+).Pentapeptide,cysteine-alanine-leacine-asparagine-asparagine(CALNN),functionalized gold nanoparticles(GNPs) were aggregated in the presence of the divalent metal ion in solution by an ion-templated chelation process,which caused an easily measurable change in the absorption spectrum of the particles.Typically,mono-dispersing GNPs exhibit an absorption band at 522 nm,corresponding to a red color solution,while aggregated GNPs have it at longer wavelengths,corresponding to a purple or blue color solution.The chelation/aggregation process is reversible via the addition of a strong metal ion chelator such as EDTA.Highly selective and sensitive detection of Pb2+ in aqueous solution is thus provided.A detection limit of 0.1 μmol/L of Pb2+ was demonstrated.     

An Efficient Approach to Spirosesquiterrenes. Synthesis of (±)β-Vetivone.

(±)β-Vetivone and (±) 10-epi-β-vetivone have been synthesized in 6 steps via an efficient spiroannelation-functionalization sequence.     

The First Efficient Approach from α-(-)-Santonin to Dihydroagarofuran Sesquiterpene

The naturally occurring dihydroagarofuran compounds have been demonstrated to show some important bioactive activities, such as insect antifeedant, antitumor activities.¹ Synthetic research of this kind of compounds have been attracting the increasing interest of organic chemists. Because a total synthesis of polyol skeleton involved too many steps,² our synthetic efforts are focusing on search for a short and efficient approach and thus, we begin with readily available α-(-)-santonin(1). The creative key steps include generation of C₅-OH, the stereochemical reversion at C-7 and the cyclization of tetrahydrofuran. A successful approach is shown in the following scheme.     

Microwave-Assisted Oxidation of α-Substituted Carbonyl Compounds to Carboxylic Acids in Aqueous Media

Carbonyl compounds containing electron-withdrawing substituents are efficiently oxidized by aqueous sodium hypochlorite in the absence of added organic solvents using microwaves.     

Zinc–Proline Complex: An Efficient,Reusable Catalyst for Direct Nitroaldol Reaction in Aqueous Media

Zinc–proline complex is an effective homogeneous catalyst for the nitroaldol reaction to afford 2‐nitro alcohols in high yields at room temperature in water. The catalyst is reused for several cycles with consistent activity.     

Ce(III)在辣根体中的迁移

应用放射性同位素示踪法, 即结合放射自显影和液体闪烁器检测及电镜放射自显影技术, 首次定性、定量地研究Ce(III)离子在辣根植物中的迁移. 结果表明: (1) Ce(III)离子能被辣根植物吸收并随时间发生迁移; (2)电镜放射自显影结果显示, Ce(III)离子迁移是通过质外体至共质体进入细胞的. Ce(III)离子在辣根植物体中的行为, 为稀土离子植物环境效应机理及辣根植物安全防护提供借鉴.     

Thermodynamic Features of the Complexation of Neodymium(III) and Americium(III) by Lactate in Trifluoromethanesulfonate Media

The protonation of lactate has been studied in a variety of electrolyte solutions using microcalorimetry to reveal a distinct medium influence imposed on the thermochemistry of the equilibrium. The thermochemistry of lactate protonation, when studied directly in 1.0 mol⋅L⁻¹ sodium lactate, agreed well with the studies performed in trifluoromethanesulfonate (triflate). This thermodynamic agreement suggests that the physical chemistry of lactate in the solutions applicable to the TALSPEAK process—a solvent extraction method for separating trivalent actinides from trivalent lanthanides within the scope of used nuclear fuel processing efforts—may be simulated in triflate solutions. Potentiometry, spectrophotometry and microcalorimetry have been subsequently used to study the thermodynamic features of neodymium and americium complexation by lactate using triflate as a strong background electrolyte. Three successive mononuclear lactate complexes were identified for Nd(III) and Am(III). The stability constants for neodymium, β ₁₀₁=2.60±0.01, β ₁₀₂=4.66±0.02 and β ₁₀₃=5.6±0.1, and for americium, β ₁₀₁=2.60±0.06, β ₁₀₂=4.7±0.1 and β ₁₀₃=6.2±0.2, were found to closely agree with the thermodynamic studies reported in sodium perchlorate solutions. Consequently, the thermodynamic medium effect, imposed on the TALSPEAK-related solution equilibria by the presence of strong background electrolytes such as NaClO₄ and NaNO₃, does not significantly impact the speciation in solution.     

Introducing the Chiral Transient Directing Group Strategy to Rhodium(III)-Catalyzed Asymmetric C−H Activation

The chiral transient directing group (TDG) strategy has been successfully introduced to the rhodium(III)-catalyzed asymmetric C−H activation. In the presence of a catalytic amount of a chiral amine and an achiral rhodium catalyst, various chiral phthalides were synthesized from simple aldehydes with high chemoselectivity, regioselectivity, and enantioselectivity (53 examples, up to 73 % yield and >99 % ee). It is noteworthy that the chiral induction model is different from the previously reported chiral TDG system using amino acid derivatives and palladium salts. The imino group generated in situ from chiral amine and aldehyde acts as the monodentate TDG to promote the C−H activation, stereoselectively generating the chiral rhodacycle bearing a chiral metal center. Moreover, the stereogenic center of the product is created and stereocontrolled during the Grignard-type addition of the C−Rh bond to aldehyde, rather than during the C−H activation step.     

Rhodium(III)-Catalyzed Asymmetric Access to Spirocycles through C−H Activation and Axial-to-Central Chirality Transfer

Axial-to-central chirality transfer is an important strategy to construct chiral centers, where the axially chiral reagents are mostly limited to atropomerically stable ones. Reported herein is a Rh^III-catalyzed enantioselective spiroannulative synthesis of nitrones. The coupling proceeds via C−H arylation to give an atropomerically metastable biaryl, followed by intramolecular dearomative trapping under oxidative conditions with high degree of chirality transfer.     

Ligand-Promoted Rhodium(III)-Catalyzed ortho-C−H Amination with Free Amines

Ligand development for rhodium(III)-catalyzed C−H activation reactions has largely been limited to cyclopentadienyl (Cp) based scaffolds. 2-Methylquinoline has now been identified as a feasible ligand that can coordinate to the metal center of Cp*RhCl to accelerate the cleavage of the C−H bond of N-pentafluorophenylbenzamides, providing a new structural lead for ligand design. The compatibility of this reaction with secondary free amines and anilines also overcomes the limitations of palladium(II)-catalyzed C−H amination reactions.     

Kinetics and Mechanism of Iridium(Ⅲ)-Catalyzed Oxidation of Ethanol Amine by Cerium(Ⅳ) in Sulfuric Acid Media

In this study, the kinetics and mechanism of the iridium(Ⅲ)-catalyzed oxidation of ethanol amine(EAN) by cerium(Ⅳ) in a sulfuric acid medium was investigated using titrimetric technique of redox in a temperature range of 298-313 K. It was found that the reaction is of first order with respect to Ce(Ⅳ) and Ir(Ⅲ), and a positive fractional order with respect to EAN. It was also found that the pseudo-first-order([EAN](》)[Ce(Ⅳ)]) rate constant kobs decreases with the increase of [H ] and [HSO-4]. Under the protection of nitrogen gas, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism was proposed. From the dependence of kobs on the concentration of hydrogen sulfate, Ce(SO4)2 was found to be the kinetically active species. The rate constants of the rate-determining step together with the activation parameters were evaluated.     

Co(III), Rh(III) & Ir(III)-Catalyzed Direct C−H Alkylation/Alkenylation/Arylation with Carbene Precursors

Metal carbenes play a pivotal role in transition-metal-catalyzed synthetic transfer reactions. The metal carbene is generated either from a diazo compound through facile extrusion of N₂ with a metal catalyst or in situ generated from other sources like triazoles, pyriodotriazoles, sulfoxonium ylides and iodonium-ylide. On the other hand, Co(III), Rh(III) & Ir(III)-catalyzed C−H functionalizations have been well established as a key synthetic step to enable the construction of various synthetic transformations. Interestingly, in recent years, merging of these two concepts C−H activation and carbene migratory insertion gained much attention, in particular group 9 metal-catalyzed arene C−H functionalizations with carbene precursors via carbene migratory insertion. In this review, we summarize recent advances in Co(III), Rh(III) & Ir(III)-catalyzed direct C−H alkylation/alkenylation/arylation with carbene precursors and also discuss key synthetic intermediates within the catalytic cycles.     

Studies on Micellization of a Polystyrene-b-poly(acrylic acid) Copolymer in Aqueous Media by Pyrene Fluorescence

The aggregation of amphiphilic block copolymers is a crucial phenomenon that controls various applications, and has been extensively treated in the literature1-3. Pyrene is a widely used fluorescence probe for the relative intensities of the vibrational fine structure (five bands) of its fluorescence spectra have been found to be sensitive to the polarity of its environment, the so-called Ham effect4. We report the studies of the aggregation properties of a PS-b-PAA copolymer using pyrene …     

Studies on Micellization of a Polystryene-b-poly(acrylic acid) Copolymer in Aqueous Media by Pyrene Fluorescence

Pryene probe and TEM have been employed to investigate the behavior of polystyrene-b-poly (acrylic acid)(PS-b-PAA) copolymer in aqueous solution.A significant annealing temperature effect on the I1/I3 ratio of pyrene was observed and was interpreted in terms of the morphological change of micellar cores.Annealing at a temperature higher than the glass transition temperature(Tg) of PS leads to densification of the hydrophobic core.     

Viscosity of Potassium Trioxalato Complexes of Al(III), Fe(III), Co(III), and Cr(III) in Aqueous Solution Between 15° and 35°C

The viscosity of dilute aqueous solutions of K₃[AI(ox)₃]·3H₂O, K₃[Fe(ox)₃]·3H₂O, K₃[Co(ox)₃]·3H₂O, and K₃[Cr(ox)₃]·3H₂O complexes, as well as K₂(ox)·H₂O, were measured between 15 and 35°C. Those of CoCl₂, 6H₂O, FeCl₃, A1₂(SO₄)₃·18H₂O, and CrCl₃·6H₂O were measured at 25°C. These data were analyzed by the Jones–Dole equation. The ionic B coefficients of the above complex anions were discussed in terms of ion–solvent interactions and the overall change in B associated with complex formation.     

Capillary Zone Electrophoresis of Iridium(III) and Ruthenium(II) Polypyridyl Complexes in Non‐Aqueous Solvents

Abstract

A method of non‐aqueous capillary zone electrophoresis has been optimised for the characterisation of five functionalised mixed‐ligand iridium(III) polypyridyl complexes and four functionalised ruthenium(II) bis‐terpyridine complexes. Their mobilities, the relation to their molar mass and the capillary lifetime (measured in number of injections) have been determined.