Copper-catalyzed functionalization of enynes

The copper-catalyzed functionalization of enyne derivatives has recently emerged as a powerful approach in contemporary synthesis. Enynes are versatile and readily accessible substrates that can undergo a variety of reactions to yield densely functionalized, enantioenriched products. In this perspective, we review copper-catalyzed transformations of enynes, such as boro- and hydrofunctionalizations, copper-mediated radical difunctionalizations, and cyclizations. Particular attention is given to the regiodivergent functionalization of 1,3-enynes, and the current mechanistic understanding of such processes.

The copper-catalyzed functionalization of enynes is a powerful approach to yield densely functionalized products. This review covers various transformations, such as boro- and hydrofunctionalizations, copper-mediated radical difunctionalizations, and cyclizations.     

Tridentate Schiff base and 4,4′-bipyridine coordinated di/polynuclear Cu (II) complexes: Synthesis,crystal structure,DNA/protein binding and catecholase activity

4,4′-bipyridine bridged two Cu (II) complexes, [Cu₂L¹₂(4,4′-bipy)(H₂O)₂](ClO₄)₂ ( 1 ) and [Cu₂L²₂(4,4′-bipy)]_n·(2H₂O)_n ( 2 ) (where, HL¹ = 2-[(3-methylamino-propylimino)-methyl]-phenol, H₂L² = 3-[(2-hydroxy-3-methoxy-benzylidene)-amino]-propionic acid, and 4,4′-bipy = 4,4′-bipyridine) have been synthesized and characterized by single crystal structure determination, mass spectrometry, FT-IR, electronic absorption, and emission spectroscopy. Complex 1 is dinuclear cationic compound and counter balanced by perchlorate anion, whereas complex 2 possesses 1D poly-nuclear structure. Both the complexes crystallize in monoclinic system with P2₁/c space group and the copper centers possess square pyramidal geometry. H-bonding, C-H···π, π···π interactions results the formation of two dimentional supramolecular structure for both the complexes. Interactions of complexes with bovine serum albumins (BSA) and human serum albumins (HSA) have been studied by using electronic absorption and emission spectroscopic technique. The calculated values of binding constants (K_b) are (9.22 ± 0.26) × 10⁵ L mol⁻¹ ( 1 -BSA), (7.19 ± 0.16) × 10⁵ L mol⁻¹ ( 1 -HSA), (5.05 ± 0.20) × 10⁵ L mol⁻¹ ( 2 -BSA) and (3.56 ± 0.25) × 10⁵ L mol⁻¹ ( 2 -HSA). The mechanism of serum albumins-complex interactions have been investigated by fluorescence lifetime measurement. Fluorescence spectroscopic studies indicate that both the complexes interact with calf thymas-DNA. Catecholase activity of the complexes has been studied in methanol using 3,5-di-tert-butylcatechol (3,5-DTBC) as substrate and the result show that both the complexes are active for catalytic oxidation of 3,5-DTBC to 3,5-di-tert-butylquinone (3,5-DTBQ) in presence of molecular oxygen. Calculated values of turnover numbers are 71.81 ± 1.04 h⁻¹ and 69.45 ± 0.74 h⁻¹ for 1 and 2 , respectively.     

The water‐promoted Diels–Alder reaction in quaternary ammonium salts

Prevailing classification of salts based on their effect in solubility and stability of proteins in aqueous solution predicts that tetraalkylammonium salts, guanidinium chloride (GnCl), LiClO₄ act as salting‐in (S/I) and LiCl, NaCl act as salting‐out (S/O) in aqueous conditions. In the same context the behaviour of GnCl, LiClO₄ and LiCl are contradictory in polar solvents like ethylene glycol and formamide. In these solvents, expected salt effect shows just opposite nature from their usual expectation. However, in the aqueous solution salts like tetraalkylammonium halide (R₄NX, R = alkyl group, X = Br group) behave like salting‐in salts. The physicochemical origin of the salting in effect of R₄NX type of salts has been discussed elaborately in the present work. The role of cations in terms of substitution of various alkyl groups on R₄NX has been systematically presented here on the basis of experimental kinetic and thermodynamic studies. The abnormal behaviour of R₄NX salts in aqueous solution has also been explained by the Setschenov equation (k_s) and Δμ_solvation values, which highlights their individual nature out of common properties of R₄NX. Copyright © 2015 John Wiley & Sons, Ltd.     

求解复杂湍流的非线性涡黏性系数模型和代数应力模型

非线性涡黏性系数模型和代数应力模型联系了线性涡黏性系数湍流模型和完整的微分 雷诺应力模型.随着它们受到日益关注,其形式也越来越多样化.本篇综述的目的是对这些模 型加以总结并比较它们之间的共同点及不同之处,指出它们与完整微分雷诺应力模型之间的 关系,以及相对于线性涡黏性系数模型而言它们在预报流场上所具有的优势.     

From Glucose to Polymers: A Continuous Chemoenzymatic Process

Efforts to synthesize degradable polymers from renewable resources are deterred by technical and economic challenges; especially, the conversion of natural building blocks into polymerizable monomers is inefficient, requiring multistep synthesis and chromatographic purification. Herein we report a chemoenzymatic process to address these challenges. An enzymatic reaction system was designed that allows for regioselective functional group transformation, efficiently converting glucose into a polymerizable monomer in quantitative yield, thus removing the need for chromatographic purification. With this key success, we further designed a continuous, three-step process, which enabled the synthesis of a sugar polymer, sugar poly(orthoester), directly from glucose in high yield (73 % from glucose). This work may provide a proof-of-concept in developing technically and economically viable approaches to address the many issues associated with current petroleum-based polymers.     

Sulfonated polysulfone-preparative routes and applications in membranes used for pressure driven techniques

There is much enthusiasm now-a-days for efforts to improve membrane performances. Membrane modification is one of the critical approaches needed for the development of membrane science and technology. The beauty of research in this orientation is that it is a dynamic process that moves forward slowly and recommendations are made based on the science available. In this regard sulfonation of polysulfones is an excellent move. The present review demonstrates different sulfonation strategies of polysulfones as well as promoting applications in pressure driven separation sciences (viz. salt, macromolecule, organic separation from water). It shows that marked path is promising one.     

A turn on ESIPT probe for rapid and ratiometric fluorogenic detection of homocysteine and cysteine in water with live cell-imaging

5(Benzothiazol-2-yl)-4-hydroxyisophthalaldehyde (BHI), an intense ESIPT containing molecule in mixed media loses its properties due to resonance-assisted H-bond (RAHB) in absolute water. Due to resonance-assisted H-bond the o-aldehyde is more reactive than the other one. With addition of cysteine/homocysteine into this solution the o-aldehyde group gets transformed into thiazolidine/thiazine ring, respectively, and the phenolic proton becomes free enough for transfer to nitrogen of the benzothiazole ring in excited state, that is, the ESIPT of BHI is turned on. Thus we can detect cysteine/homocysteine in water as well as in live cells.     

Invoking Pairwise Interactions in Water‐Promoted Diels–Alder Reactions by using Ionic Liquids as Cosolvents

Rate constants and derived activation parameters of organic reactions in aqueous media, in particular Diels–Alder reactions, are sensitive to the presence of cosolvents in water. To enhance the solubility window of water, we introduced ionic liquids as cosolvents in the aqueous Diels–Alder reaction between anthracene‐9‐carbinol and N‐ethylmaleimide. The reactive potentials of the organic compounds are parameterized by using semi‐empirical quantum chemical methods. The principle of Savage–Wood additivity of group interactions is used to quantify the pairwise group interactions among chemically inert ionic liquids and organic reactants, both at initial and transition states of the reaction. The present approach shows promise, as the use of simple calculations from easily available kinetic data can help researchers to understand the versatility of green ionic‐liquid alternatives to volatile organic solvents.