Electrosynthesis of cinnamic acid by electrocatalytic carboxylation of phenylacetylene in the presence of [NiII(Me4-NO2Bzo[15]tetraeneN4)] complex: An EC′CCC′C mechanism

A Ni(II) complex, [Ni^II(Me₄-NO₂Bzo[15]tetraeneN₄)], was used for electrocatalytic reduction of CO₂ in acetonitrile solvent. Then, the reduced form of CO₂ (CO₂^?) was used for selective carboxylation of phenylacetylene to produce cinnamic acid at room temperature. The potential of the process is significantly less negative in comparison with those reported earlier. Using sacrificial magnesium electrode as anode, controlled potential coulometry was carried out in an undivided glass cell. The spectral characterizations of FTIR, ¹H NMR, and ¹³C NMR demonstrated that cinnamic acid was the main product of the electrolysis. With respect to other catalysts, which have been previously reported in the literature, application of the Ni(II) complex in carboxylation of unsaturated compounds has three advantages: (1) the selectivity in the production of cinnamic acid; (2) more increase in the reduction current indicating that the carboxylation of phenylacetylene is fast; and (3) the potential shift of electrocatalytic reduction of CO₂ to less negative values showing that the Ni(II) complex has an excellent electrocatalytic activity for CO₂ reduction. According to the voltammetric and coulometric results, an EC′CCC′C mechanism was proposed for the electrocatalytic synthesis of cinnamic acid.     

Surface-imprinted polymers in microfluidic devices

Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction sites for the noncovalent bonds become "frozen" in the cross-linking polymer and maintain their shape even after the template is removed. The resulting cavities reproduce the size and shape of the template and can selectively reincorporate the template when a mixture containing it flows over the imprinted surface. In the last few decades the field of molecular imprinting has evolved from being able to selectively capture only small molecules to dealing with all kinds of samples. Molecularly imprinted polymers (MIPs) have been generated for analytes as diverse as metal ions, drug molecules, environmental pollutants, proteins and viruses to entire cells. We review here the relatively new field of surface imprinting, which creates imprints of large, biologically relevant templates. The traditional bulk imprinting, where a template is simply added to a prepolymer before curing, cannot be applied if the analyte is too large to diffuse from the cured polymer. Special methods must be used to generate binding sites only on a surface. Those techniques have solved crucial problems in separation science as well as chemical and biochemical sensing. The implementation of imprinted polymers into microfluidic chips has greatly improved the applicability of microfluidics. We present the latest advances and different approaches of surface imprinting and their applications for microfluidic devices.     

Studying of antifungal activity of functionalized multiwalled carbon nanotubes by microwave‐assisted technique

In this paper, we reinforced the antifungal activity of multi‐walled carbon nanotubes (MWCNTs) using an effective technique. Covalent functionalization of MWCNTs was performed by lysine and arginine under microwave radiation. To prove functionalization phenomenon, the grafted chemical groups on the surfaces of MWCNTs were analyzed by Fourier transform infrared and Raman spectroscopy. Antifungal activities of functionalized MWCNTs as well as pristine MWCNTs were tested against different fungal species based on minimal inhibitory concentration (MIC) and radial diffusion assay. MIC results showed that the antifungal activity of MWCNTs‐lysine, in comparison to pristine MWCNTs against fungi, including Aspergillus niger, Aspergillus fumigatus, Candidate albicans, Penicillium chrysogenum, Saccharomyces cerevisiae, Fusarium culmorum, Microsporum canis, Trichophyton mentagrophytes, Trichophyton rubrum and Penicillium lilacinum were increased 1.92, 2.36, 2.35, 1.3, 1.5, 1.1, 2.54, 1.23, 1.42 and 2.1 times, respectively. Similarly, the antifungal activity of MWCNTs‐arginine was increased 1.98, 2.40, 2.55, 1.8, 1.9, 1.7, 2.64, 1.36, 2.1 and 2.55 times, respectively. On the basis of the results of this study, it is clearly indicated that covalent groups of lysine and arginine could improve the antifungal activity of MWCNTs. Copyright © 2012 John Wiley & Sons, Ltd.     

KF/Al2O3 as a Highly Efficient,Green, Heterogeneous,and Reusable Catalytic System for the Solvent-Free Synthesis of Carboacyclic Nucleosides via Michael Addition Reaction

KF/Al₂O₃ acts as an efficient catalytic system for the synthesis of carboacyclic nucleosides via Michael addition of pyrimidine and purine nucleobases to α,β-unsaturated esters under solvent-free and microwave conditions. Using this method, the title compounds are produced in good to excellent yields and short reaction times.     

Reductive Amination of Aldehydes and Ketones Under Heterogeneous and Solvent-Free Conditions Using Sodium-Borohydride and Silica-Gel–Supported Sulfuric Acid

A regioselective and convenient procedure for preparation of amines by reductive amination of aldehydes and ketones using sodium borohydride in the presence of sulfuric acid supported on silica gel as an active, inexpensive, and recoverable catalyst under heterogeneous and solvent-free conditions at room temperature is described.     

MOF‐promoted Three‐component Synthesis of Functionalized Pyrano[3,2‐c]chromen under Mild Conditions

A convenient and efficient route for synthesis of various derivatives of 3‐benzoyl‐4‐phenyl‐2‐(trifluoromethyl)pyrano[3,2‐c]chromen‐5(4H)‐one has been used via tandem Knoevenagel condensation–Michael addition and intramolecular cyclization sequence. These products have been synthesized in the presence of catalytic amount of metal–organic framework (MOF) and potassium carbonate as one‐pot, three‐component reaction. MOF catalyst has been separated easily with external magnet, and high purity of products has been obtained after washing with ethanol. This protocol has advantages of simplicity, mild condition, and high yield. More importantly, MOF has been easily recycled for three times.     

Synthesis,characterization and application of nano-N,N,N′,N′-tetramethyl-N-(silica-n-propyl)-N′-sulfo-ethane-1,2-diaminium chloride as a highly efficient catalyst for the preparation of N,N′-alkylidene bisamides

Research on Chemical Intermediates - A novel mesoporous nanomaterial, namely nano-N,N,N′,N′-tetramethyl-N-(silica-n-propyl)-N′-sulfo-ethane-1,2-diaminium chloride...     

Convenient Ultrasound-Promoted Regioselective Synthesis of Fused 6-Amino-3-methyl-4-aryl-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile

A multicomponent, catalyst-free reaction for the synthesis of fused 6-amino-3-methyl-4-aryl-1H-pyrazolo [3,4-b] pyridine-5-carbonitrile from 3-amino-5-methylpyrazole, malononitrile, and substituted aldehydes under ultrasound irradiation in short reaction times (8–10 min) with good yields (85–98%) is reported.

Molybdate sulfonic acid: preparation, characterization, and application as an effective and reusable catalyst for octahydroxanthene-1,8-dione synthesis

Molybdate sulfonic acid (MSA) as a highly efficient catalyst was synthesized and employed for the synthesis of octahydroxanthene-1,8-dione derivatives. MSA efficiently catalyzed condensation of a wide range of aryl aldehydes and cyclohexane-1,3-diones to obtain octahydroxanthene-1,8-diones. It was characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), and FT-IR spectroscopy. This catalyst can be recovered and reused several times in other reactions maintaining its high activity. This novel and green method is very cheap and has many advantages such as excellent yields, the use of recoverable and eco-friendly catalysts, and a simple work-up procedure.     

Interaction Modes and Absolute Affinities of α‐Amino Acids for Mn2+: A Comprehensive Picture

Manganese is involved as a cofactor in the activation of numerous enzymes as well as the oxygen‐evolving complex of photosystem II. Full understanding of the role played by the Mn²⁺ ion requires detailed knowledge of the interaction modes and energies of manganese with its various environments, a knowledge that is far from complete. To bring detailed insight into the local interactions of Mn in metallopeptides and proteins, theoretical studies employing first‐principles quantum mechanical calculations are carried out on [Mn‐amino acid]²⁺ complexes involving all 20 natural α‐amino acids (AAs). Detailed investigation of [Mn‐serine]²⁺_, [Mn‐cysteine]²⁺, [Mn‐phenylalanine]²⁺, [Mn‐tyrosine]²⁺, and [Mn‐tryptophan]²⁺ indicates that with an electron‐rich side chain, the most stable species involves interaction of Mn²⁺ with carbonyl oxygen, amino nitrogen, and an electron‐rich section of the side chain of the AA in its canonical form. This is in sharp contrast with aliphatic side chains for which a salt bridge is formed. For aromatic AAs, complexation to manganese leads to partial oxidation as well as aromaticity reduction. Despite multisite binding, AAs do not generate strong enough ligand fields to switch the metal to a low‐ or even intermediate‐spin ground state. The affinities of Mn²⁺ for all AAs are reported at the B3LYP and CCSD(T) levels of theory, thereby providing the first complete series of affinities for a divalent metal ion. The trends are compared with those of other cations for which affinities of all AAs have been previously obtained.