Photoinitiated atom transfer radical polymerization: Current status and future perspectives

In macromolecular and material science, atom transfer radical polymerization (ATRP) has intensely influenced the research strategies facilitating fabrication of a wide range of polymers with well‐defined structures and functions and their conjugation with biomolecules. Recently, the required copper (I) catalyst for ATRP process is generated by photoinduced redox reactions involving the in situ reduction of Cu(II) to Cu(I). Photochemically initiated reactions provide several distinct advantages, including temporal and spatial controls, rapid and energy efficient activation. The process is based on photoredox reactions of copper catalysts under various radiation sources with or without various photoinitiators. This Highlight focuses on the historical development, mechanistic aspects, limitations, and opportunities of photoinitiated ATRP along with selected examples. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2878–2888     

Ring-opening reactions of oxetanes: A review of methodology development and synthetic applications

Ring-opening reactions of oxetanes yield important functionalized products depending upon the nature of nucleophiles as well as substitution pattern on the oxetane ring. Ring opening of oxetanes can be carried out under a variety of reaction conditions. In this review article, an up-to-date overview of major synthetic methodologies involved in the ring opening of oxetanes as well as their synthetic applications has been presented.     

Phenacyl Ethyl Carbazolium as a Long Wavelength Photoinitiator for Free Radical Polymerization

A new phenacyl‐type photoinitiator based on ethyl carbazole as a long wavelength photo­initiator is developed for free radical polymerization. Phenacyl ethyl carbazolium hexafluoroantimonate (PECH) photoinitiator is synthesized in a two‐step, one‐pot manner by quaternizing ethyl carbazole with phenacyl bromide and subsequent ion exchange reaction with potassium hexafluoroantimonate. Under irradiation, PECH tends to undergo homolytic bond cleavage bringing about initiating free radicals. However, as evidenced by cyclic voltammetry and real‐time photobleaching studies, formation of initiating cationic species is highly unlikely as the photochemically formed charged carbazole units tend to couple.

     

Synthesis and characterization of manganese ferrite nanoparticles by thermal treatment method

Cubic structured manganese ferrite nanoparticles were synthesized by a thermal treatment method followed by calcination at various temperatures from 723 to 873 K. In this investigation, we used polyvinyl pyrrolidon (PVP) as a capping agent to control the agglomeration of the nanoparticles. The characterization studies were conducted by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The average particle sizes of manganese ferrite nanoparticles were determined by TEM, which increased with the calcination temperature from 12 to 22 nm and they had good agreement with XRD results. Fourier transform infrared spectroscopy confirmed the presence of metal oxide bands at all temperatures and the absence of organic bands at 873 K. Magnetic properties were demonstrated by a vibrating sample magnetometer, which showed a super-paramagnetic behavior for all samples and also saturation magnetization (M_s) increases from 3.06 to 15.78 emu/g by increasing the calcination temperature. The magnetic properties were also confirmed by the use of electron paramagnetic resonance spectroscopy, which revealed the existence of unpaired electrons and also measured peak-to-peak line width, resonant magnetic field and the g-factor.     

Structure-based design,synthesis and biological evaluation of β-glucuronidase inhibitors

Using structure-based virtual screening approach, a coumarin derivative (1) was identified as β-glucuronidase inhibitor. A focused library of coumarin derivatives was synthesized by eco-benign version of chemical reaction, and all synthetic compounds were characterized by using spectroscopy. These compounds were found to be inhibitor of β-glucuronidase with IC₅₀ values in a micromolar range. All synthetic compounds exhibited interesting inhibitory activity against β-glucuronidase, however, their potency varied substantially from IC₅₀ = 9.9–352.6 µM. Of twenty-one compounds, four exhibited a better inhibitory profile than the initial hit 1. Interestingly, compounds 1e, 1k, 1n and 1p exhibited more potency than the standard inhibitor with IC₅₀ values 34.2, 21.4, 11.7, and 9.9 µM, respectively. We further studied their dose responses and also checked our results by using detergent Triton ×-100. We found that our results are true and not affected by detergent.     

Synthesis of Fluorescent 2,6‐Dicyano‐3,5‐Disubstituted Anilines Using Cellulose Sulfuric Acid in Aqueous Media

The synthesis of some fluorescent 2,6‐dicyano‐3,5‐disubstituted anilines using cellulose sulfuric acid (Cellulose‐SA) as an environmentally benign catalyst in H₂O is described. The one‐pot reaction of 1,3‐diketone and three equiv. of malononitrile was carried out in the presence of one equiv. of a secondary amine, Cellulose‐SA as catalyst, and H₂O as solvent. The photophysical properties (λ_Abs., λ_Flu.) of the synthesized compounds in CH₂Cl₂, MeCN, and MeOH have been measured. The emission spectra of the new compounds in the solid state are also reported.     

An in silico approach to design peptide mimetics based on docking and molecular dynamics simulation of EGFR–matuzumab complex

Epidermal growth factor receptor (EGFR) plays an essential role in anticancer therapy. Matuzumab is an antibody for the treatment of colorectal, lung and stomach cancer. Matuzumab binds efficiently to EGFR and blocks its phosphorylation. The recent clinical successes have established application of peptides for cancer treatment. The present contribution introduces an in silico approach to design peptides based on molecular dynamics simulation (MDs) of the matuzumab-EGFR complex in water environment. Moreover, principal component analysis has been used to select multiple conformations of the complex in MDs for designing the peptides. The paratope and epitope in each conformation of the complex were determined, and the alanine scanning was used to identify the hot spots of EGFR conformers. The conformations of the peptides were optimized using PEP-FOLD server and MDs. The selected conformations were analyzed in a docking study to realize the binding site of the EGFR. Finally, pharmokinetics properties of the peptides were calculated. The designed oligopeptides were EWRSYYYWH, YYYWHNEWN, YYYWHNEWS and HNHSRNYGS with a higher affinity to the EGFR relative to the previously reported peptides. The newly designed peptides were investigated for their in vivo toxicities on rats, and all of them were non-toxic.     

Catalytic polymerization of ethylene by non-metallocene Zirconium(IV) calix[4] pyrrole complexes

Some zirconium compounds containing chelating diamido dipyrrole or tetra-amido tetra-pyrrole ligands were synthesized and used as polymerization catalyst with high polymerization activity of ethylene at 40 °C and 1 bar, in presence of MAO or B(C₆F₅)₃ as co-catalyst. The maximum catalytic activity reached 1100 Kg/mol bar h for ethylene polymerization by Zr₂(octa-phenyl calix[4]pyrrolidine)Cl₄. These results reveal that half-zirconocene like complexes including four terminal chlorine and one calix[4]pyrrolidine in middle with both π and σ-interaction have the highest ethylene polymerization turnover (compounds 13, 14).