Efficient synthesis of 2-thioxo-1,3-thiazolanes from primary amines, CS2, and ethyl bromopyruvate

An efficient synthesis of 2-thioxo-1,3-thiazolanes is described via reaction of carbon disulfide, ethyl bromopyruvate, and primary amines. Correspondence: Issa Yavari, Chemistry Department, Tarbiat Modares University, PO Box 14115-175, Tehran, Iran.     

Toward efficient functionalization of polystyrene backbone through ketene chemistry: Synthesis,characterization, and DFT study

In this study, polystyrene was functionalized with Meldrum's acid toward the introduction of the ketenes (CCO) system to its backbone for producing a dramatically reactive intermediate. Meldrum's acid, as a ketene source, was reacted by poly(styrene-co-p-chloromethyl styrene) through a simple nucleophilic reaction to synthesize poly(styrene-co-styryl Meldrum's acid). Then, the pendant Meldrum's acid under thermal treatment converted to ketene intermediate resulting in highly reactive polystyrenes derivatives, which rapidly reacted by nucleophilic reagents to afford ultimate organic building blocks. The polystyrene derivatives were characterized using elemental analysis, FT-IR, high-resolution solid-state NMR, thermogravimetric analysis (TGA), and differential thermogravimetric analysis (DTG). To clarify the evolutionary mechanisms of polystyrene products, density functional theory (DFT) method B3LYP with the 6–311++G(2d,p) basis set was used. We studied the preparation of polystyrene model compounds through Meldrum's acid thermolysis and nucleophilic substitution. The kinetic and thermodynamic parameters in all reactions and the structural and electronic properties of all molecules were calculated. These data exhibited that based on Gibbs Free energy values, the structure of syndiotactic polystyrene is more stable than that of isotactic polystyrene. Furthermore, it was found that the presence of an electron donor or acceptor substituent on the polystyrene structure affects the electronic bandgap.     

Poly(4-vinylpyridinium tribromide) as metal-free and recoverable oxidizing agent for the selective oxidation of alcohols, and oxidative deprotection of trimethylsily ethers

Poly(4-vinylpyridinium tribromide) was found to be an efficient oxidizing polymer for the chemoselective oxidation of a wide range of alcohols into aldehydes and ketones. In addition it was used for the oxidative deprotection of trimethylsilyl ethers into alcohols or carbonyl compounds depending on the structure of trimethylsilyl ether.     

Theoretical study on thermal behavior of passively Q-switched microchip Nd:YAG laser

This study deals with the thermal characterization of a continuous wave (CW-) and end-pumped passively Q-switched microchip Nd:YAG laser crystal by solving the rate and heat transfer equations in the laser cavity. In this approach, a parametric study has been performed to investigate the influence of the pumping parameters, cooling metal dimension and also the crystal dimension and doping concentration on the thermal behavior of the laser crystal. Obtained results reveal a closed correlation between the mentioned parameters and the thermal behavior of the crystal indicating that a proper selection of the laser parameters is essential to control the crystal's temperature and improve the performance of the laser accordingly.     

Nanoparticle using parallel split rings and implementation of chain for creating Fano resonance with polarization independence for energy harvesting in mid-infrared

In optical devices, the polarization of the incident wave affects the Nano particle characteristics. Therefore, designing a polarization-independent device is significant in the process of designing optical structures. On the other hand, the concept of Fano resonance and dark mode has been utilized for achieving more energy enhancement. In this paper, we have developed a symmetrical Nano antenna by employing Fano resonance, which is independent of the incident wave polarization. The proposed Nano antenna is modified in mid infrared regime for biosensing and energy harvesting applications. The designed metamaterial antenna is made by Nano split ring resonators with etched capacitive gaps, which are utilized for concentrating energy. The introduced Nano antenna has a bright and dark mode with a weak enhancement of electric field. The effect of the incident wave polarization is investigated at wave incident angles between 0° and 45° to illustrate the independency of the polarization due to the symmetrical shape of the Nano antenna. In order to trigger the dark mode and enhance the electric field, a Nano chain is incorporated in the final structure. This arrangement has led to increasing of electric field drastically. Furthermore, the figure of merit has been calculated as an advantageous factor in sensing the surrounding materials with various refractive indices. Our findings illustrated that the chain arrangement has caused a peak in the linear form of the extinction cross section of the Nano antenna. This in turn has resulted in the appearance of Fano resonance with no impact on the resonance frequency that has been originally adjusted by capacitive gaps and inductive strips.     

Naphthoflavone propargyl ether inhibitors of cytochrome P450

Cytochrome P450 enzymes protect the body from foreign substances through a mechanism that involves oxidation of those substances into more readily excretable polar compounds. It has been shown that some naphthoflavones function as substrates of certain P450 enzymes (CYP1A1 and CYP1B1) and with appropriate structural changes may become inhibitors. Moreover, propargyl ether derivatives of adamantane have been shown to function as selective inactivators of some P450 enzymes (CYP2B1 and CYP2B5). In an attempt to improve the potency and selectivity of inhibition, we have designed and synthesized a series of naphthoflavone propargyl ethers. We report here the synthesis, X-ray crystal structures, and inhibition data (IC₅₀ of EROD inhibition in CYP1A1 and CYP1B1 enzymes) of α-naphthoflavone 2′-propargyl ether, β-naphthoflavone 2′-propargyl ether, α-naphthoflavone 4′-propargyl ether, and β-naphthoflavone 4′-propargyl ether. Crystallographic data: α-naphthoflavone 2′-propargyl ether, , a=7.775(1) ?, b=8.062(1) ?, c=13.110(1) ?, α=84.32(1)°, β=75.42(1)°, γ=86.56(1)°, V=790.8(2) ?³; β-naphthoflavone 2′-propargyl ether, , a=7.605(2) ?, b=7.793(1) ?, c=14.167(2) ?, α=77.06(1)°, β=75.41(1)°, γ=89.54(1)°, V=790.9(2) ?³; α-naphthoflavone 4′-propargyl ether, P21/n, a=14.595(2) ?, b=4.708(1) ?, c=24.745(6) ?, β=106.31(2)°, V=1631.8(7) ?³; β-naphthoflavone 4′-propargyl ether, P1, a=4.8871(5) ?, b= 7.9597(7) ?, c=21.788(3) ?, α=81.771(9)°, β=89.918(10)°, γ=72.223(8)°, V= 797.9(2) ?³.     

Polyvinyl amine as a modified and grafted shell for Fe3O4 nanoparticles: As a strong solid base catalyst for the synthesis of various dihydropyrano[2,3-c]pyrazole derivatives and the Knoevenagel condensation

In this work, we reported one-step deposition of polyacrylamide on nano-magnetite surface via a simple and in situ polymerization of acryl amide to form n-Fe₃O₄/PAM nanocomposite. The amide (–CONH₂) groups could be converted easily to amine (–NH₂) groups through Hofmann degradation to introduce n-Fe₃O₄/PVAm as a highly efficient heterogeneous base catalyst. The obtained organic-inorganic nanocomposite exhibited high catalytic activity for the solvent-free syntheses of various dihydropyrano[2,3-c]pyrazole derivatives and the Knoevenagel condensation in high to excellent yields and in the following, a plausible mechanism for the synthesis of them has been proposed. Because of the polymer layer coated Fe₃O₄ nanoparticles, the catalyst has many catalytic units, and acceptable thermal stability and recyclability. Titration, FT-IR, SEM, TGA, VSM, and XRD analysis were used for characterization of the catalyst. Also, the nanocomposite can be easily recovered by a magnetic field and reused up to 9 times without distinct deterioration in catalytic activity.