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  • Open access
  • 47 Reads
Highly asymmetric reduction of new benzofuryl and benzothiophenyl α-amino ketones

Heterocyclic compounds play an important role in the medicinal chemistry and occupy a central position in synthetic organic chemistry. Both benzofuran and benzothiophene are considered as very important structures due to their diverse biological and pharmacological profile. Many of the clinically approved drugs are synthetic and naturally occurring substituted benzofuryl and benzothiophenyl derivatives in conjunction with other heterocycles. Therefore a new series of α-amino ketones (containing various azole rings) derivatives of benzofuran and benzothiophene were synthesized and subjected to the transfer hydrogenation with formic acid, catalyzed by RhCl[(R,R)-TsDPEN](C5Me5). The corresponding optically active β-amino alcohols were obtained in high yields and excellent enantioselectivities (93-99%), as determined by chiral HPLC. The absolute configuration of the products was confirmed by means of ECD spectroscopy supported by theoretical calculations.

  • Open access
  • 81 Reads
Removal of Hg2+ heavy metal ion using a highly stable metal-organic framework

The zirconium-based metal-organic framework with 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) linker known as PCN-221 was successfully synthesized by the solvothermal method. Characterization of the MOF was performed using various techniques, such as FT-IR, XRD, UV-Vis, and SEM analysis. The MOF has then applied to rapidly and efficiently adsorption of mercury (Hg2+) ions using an ultrasonic bath. Different parameters such as initial metal ion concentration, contact time, solution pH and adsorbent dose were investigated. The presence of a nitrogen-functionalized group in the porphyrin ligand in PCN-221 structure contributed to the absorption of mercury ions. The adsorption capacity of 233 mg g-1 was obtained for this adsorbent in less than 30 minutes at pH = 7. The experimental adsorption data for the PCN-221 MOF are well suited with the pseudo-second-order kinetic model (R2 = 0.99), and adsorption isotherms of Pb2+ metal ions are in good agreement with the Langmuir model.

  • Open access
  • 80 Reads
An amine/azine functionalized MOF as a new fluorescent probe for selective sensing of metal ions

Metal-organic frameworks are a class of attractive materials for fluorescent sensing. Here, we report the exploration of fluorescent Zn-based amine/azine-functionalized MOF, TMU-17-NH2, ([Zn(NH2-BDC)(4-bpdb)].2DMF; NH2-BDC = amino-1,4-benzenedicarboxylic acid, 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-2,3-butadiene) for highly selective and sensitive detection of Fe3+ in DMF solution. TMU-17-NH2 shows fast recognition of Fe3+ ion with a response time of <1 min and a detection limit of 0.7 µM (40 ppb), and the luminescence is completely quenched in 10-3 M DMF solution of Fe3+. Furthermore, the static quenching constant is calculated to be upper than 41000 M-1 by the fluorescence titration experiment in low concentration of Fe3+. No interferences from 250 μM As3+, Cd2+, Zn2+, Co3+, Ni2+, Cu2+, Pb2+, Mn2+ and Al3+ were found for the detection of Fe3+. The efficient fluorescent quenching effect is attributed to the photoinduced electron transfer between Fe3+ ions and the amino-functionalized ligand in this MOF. Moreover, the introduced azine N donors in the 4-bpdb ligand of TMU-17-NH2 additionally donate their lone-pair electrons to the Fe3+ ions, leading to significantly enhanced detection ability. Furthermore, the regenerated TMU-17-NH2 still has high selectivity for Fe3+ ions, which suggests that the functionalized TMU-17-NH2 is a promising luminescent probe for selectively sensing iron ions.

  • Open access
  • 27 Reads
Synthesis of 2-amino-apopinan-3-ol and applications of its derivatives in asymmetric reduction of ketones

Monoterpenes are optically active compounds which occurs in nature. This fact makes them interesting precursors for the synthesis of optically active ligands, which can be applied in various asymmetric reactions.

In this work, we present the synthesis of optically pure 2-amino-apopinan-3-ol from (–)-α-pinene. Next, the obtained amino alcohol was used as a precursor of oxazaborolidines, which were used as catalysts in the asymmetric reduction of aryl-alkyl ketones with borane. In the second part, we transformed 2-amino-apopinan-3-ol into PHOX ligand in a three-step reaction. The complex of ruthenium precursor with PHOX ligand was used as a catalyst in the asymmetric transfer hydrogenation of aryl-alkyl ketones. Alcohols with enantiomeric excesses of up to 97% were isolated using both ketone reduction methods.

  • Open access
  • 160 Reads
Efficient Fluorescence detection of Fe3+, Cd2+, and CH2Cl2 based on an azine-Functionalized Zn-Metal-Organic Framework

The design and synthesis of sensitive and selective luminescent materials as chemical sensing agents is a fundamental goal in fluorescence assays. Considering high porosity, large surface area, excellent photoluminescence property of metal-organic frameworks (MOFs), luminescent properties of a microporous azine-functionalized MOF, TMU-16, dispersed in different metal ions and solvents have been investigated systematically. The TMU-16 displays superb luminescence emission, and it can detect Fe(III) and Cd(II) ions with high selectivity, excellent sensitivity, and short response time (<1 min). The emission intensities of TMU-16 were quenched upon the addition of Fe(III) and increased upon the addition of Cd(II). The effect of other metal ions on the fluorescence intensity of the MOF was also studied and other metal ions showed low interference response in recognition of Fe(III) and Cd(II). More importantly, this is the first example of MOF-based luminescent sensor as efficient multifunctional fluorescence material which can use for selective sensing of Fe(III) and Cd(II) ions and small molecules such as CH2Cl2.

  • Open access
  • 84 Reads
Synthesis of an Adamantane-based Tetralactam and its Complexation with Dicarboxamides

Tetralactam macrocycles are suitable candidates to be employed as synthetic receptors for charged or neutral guests. In the sensing of neutral molecules non polar solvents such as chloroform or dichloromethane are usually employed since the hydrogen-bonded interactions can be established. Thus one of its main limitations of the studied macrocycles is their low solubility in these solvents.

Herein we describe the synthesis of an adamantane-based tetralactam macrocycle which is partially soluble in chlorinated solvents. For this purpose, by following a clipping methodology, we firstly synthesized a kinetically stable pseudorotaxane having a removable tetraalkylfumaramide thread and the desired macrocycle. A subsequent thermal dethreading straightforwardly yielded the adamantane-based macrocycle. Afterwards the affinity of the adamantane-derived macrocycle for a series of symmetric and non-symmetric fumaramides and succinamides guests was studied, calculating the association constants when the corresponding [2]pseudorotaxanes are assembled.

  • Open access
  • 113 Reads

Cancer is one of the most researched areas nowadays due to the increasing incidences of cancer patients and unavailability of cheap and highly efficient drugs. Cancer is the uncontrolled proliferation of the body’s own cell. The cancer cells are dedifferentiated and lose their normal function. We are aware of the fact that the cancer cells differ from normal cells in many aspects. One such aspect is pH of cancer cells. The cancer cell has a pH lower than that of the normal cells of the body. In this research, we have prepared target-specific and pH-sensitive bioactive polymer using a combination of different natural polymer like polyvinyl alcohol, sodium alginate in a different ratios. Since, these polymers are pH sensitive, they will release the loaded drug only at the cancer site thus reducing the various side effects of the drug and drug toxicity.

  • Open access
  • 73 Reads
New magnetic periodic mesoporous organosilica functionalized 3-propyl amine (Fe3O4@PMO-ICS-PrNH2) as highly efficien and recyclable catalysts in one-pot synthesis of imidazopyrimidine derivatives

The catalytic application of a novel magnetic periodic mesoporous organosilica functionalized 3-propylamine(Fe3O4@PMO-ICS-PrNH2) in the synthesis of imidazopyrimidine derivatives was investigated. At first, the Fe3O4@PMO-ICS-PrNH2 nanocatalyst was prepared and characterized by N2 adsorption-desorption isotherms techniques, field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer (VSM). Then, the catalyst was shown to be a efficient recyclable and highly active catalyst and used in the three-component synthesis of 2-aminobenzaldehyde with aromatic aldehydes various and dimedone/malononitrile under H2O solvent conditions. Also, imidazopyrimidine products were obtained in mild reaction conditions, good to excellent yields and at short reaction times. Moreover, the catalyst was recovered and successfully reused at least five times without considerable reduction in its activity.

  • Open access
  • 78 Reads

Bimolecular nucleophilic substitution (SN2) reaction is one of the most frequently process choose as mechanism model to introduce undergraduate chemistry students in the computational chemistry methodology.

In this work, we performed a computational analysis for the ionic SN2 reaction, where the nucleophile charged (X-; X=F, Cl, Br, I) attacks the carbon atom of the substrate (CH3Cl) through a backside pathway and simultaneously the leaving group is displaced (Cl-). The calculations were performed applying DFT methods with the Gaussian09 program, the B3LYP functional, the 6-31+G* basis set for all atom except iodine (6-311G*) and the solvents effect (acetonitrile and cyclohexane) were evaluated with the PCM model. We evaluated the potential energy surface (PES) for the mentioned reaction considering the reactants, the formation of an initial complex between the nucleophile and the substrate, the transition state, a final complex where the leaving group is still bound to the substrate and the products. We analyzed the atomic charge (ESP) and the bond distance throughout the process. Gas phase and solvent studies were performed in order to analyze the solvation effects on the reactivity of the different nucleophiles. We observed that increasing solvent polarity, decreases reaction rates.

On the other hand, we thought it would be enriching, to carry out a reactivity analysis from the point of view of molecular orbitals. So, we analyzed the OM HOMO and the OM LUMO of the different stationary states on PES, both in a vacuum (gas phase) and in acetonitrile as the solvent.