Catalyst‐Free Photoredox Addition–Cyclisations: Exploitation of Natural Synergy between Aryl Acetic Acids and Maleimide

Suitably functionalised carboxylic acids undergo a previously unknown photoredox reaction when irradiated with UVA in the presence of maleimide. Maleimide was found to synergistically act as a radical generating photoxidant and as a radical acceptor, negating the need for an extrinsic photoredox catalyst. Modest to excellent yields of the product chromenopyrroledione, thiochromenopyrroledione and pyrroloquinolinedione derivatives were obtained in thirteen preparative photolyses. In situ NMR spectroscopy was used to study each reaction. Reactant decay and product build‐up were monitored, enabling reaction profiles to be plotted. A plausible mechanism, whereby photo‐excited maleimide acts as an oxidant to generate a radical ion pair, has been postulated and is supported by UV/Vis. spectroscopy and DFT computations. The radical‐cation reactive intermediates were also characterised in solution by EPR spectroscopy.     

Disupersilylperoxo Radical Anion [tBu3SiOOSitBu3]⋅−: An Intermediate of Supersilanide Oxidation

In the oxidative process of the supersilanide anion [SitBu₃]^?, radical species are generated. The continuous wave (cw)‐EPR spectrum of the reaction solution of Na[SitBu₃] with O₂ revealed a signal, which could be characterized as disupersilylperoxo radical anion [tBu₃SiOOSitBu₃]^?? affected by sodium ions though ion‐pair formation. A mechanism is suggested for the oxidative process of supersilanide, which in a further step can be helpful in a better understanding of the oxidation process of isoelectronic phosphanes.     

Studies on Diels–Alder thermoresponsive networks based on ether–urethane bismaleimide functionalized poly(vinyl alcohol)

Thermoreversible networks obtained by the Diels–Alder cycloaddition reaction of poly(vinyl furfural) with urethane bismaleimides containing polyether chain were synthesized. The formation of the networks was confirmed by attenuated total reflectance in conjunction with Fourier transform infrared spectroscopy (ATR–FTIR). The materials thermal properties were investigated using differential scanning calorimetry (DSC) and a coupling of dynamic thermogravimetry with Fourier transform infrared spectroscopy and mass spectrometry (TG–FTIR–MS) for pyrolysis behaviour under nitrogen atmosphere. A thermal decomposition mechanism of the networks and poly(vinyl furfural) was discussed via evolved gas analysis. The thermoreversibility of the networks was demonstrated by the presence of the endothermic peak characteristic to the retrodienic process on the DSC heating curves and also the appearance of the exothermic peak, due to the dienic process, on the DSC cooling curve. The dynamic contact angle and free surface energy values of the networks were determined. Measures of the heterogeneity and roughness of the surfaces suggested that the surfaces of the networks’ films are more homogenous than the initial poly(vinyl furfural) surface. Dynamic water vapour sorption studies were conducted.     

Probing Mass Transfer in Mesoporous Faujasite‐Type Zeolite Nanosheet Assemblies

Pulsed field gradient nuclear magnetic resonance (NMR) diffusion studies are performed by using cyclohexane to probe transport properties in a NaX‐type zeolite with a hierarchical pore structure (house‐of‐cards‐like assemblies of mesoporous nanosheets), which is compared with a purely microporous sample. With guest loadings chosen to ensure saturation of the micropores, and the meso‐ and macropores left essentially unoccupied, guest diffusion is shown to be enhanced by almost one order of magnitude, even at room temperature. Diffusivity enhancement is further increased with increasing temperature, which may, therefore, be unambiguously attributed to the contribution of mass transfer in the meso‐ and macropores.     

Energetics of Spinels in the FeTiO System at the Nanoscale

The energetics of nanosized Fe/Ti spinel oxides was studied using high‐temperature oxide melt solution calorimetry. The mixing properties of the solid solution in the system were obtained, and through comparison to macroscopic materials the effect of particle size on the thermodynamics was assessed. The surface energies of the nanosized materials are similar within the errors regardless of the composition, and are consistent with those determined for other spinels. The enthalpies of oxidation to hematite plus rutile of the iron titanium spinels follow a linear trend with the Fe²⁺ content, which allows them to be calculated for any composition or particle size. The heat of formation of the macroscopic and nanosized titanomagnetites was fit as a polynomial function and the numerical coefficients are presented. The enthalpies of mixing in the titanomagnetite and titanomaghemite solid solutions are similar at the macroscopic and nanoscale.     

Photonic crystals obtained by soap-free emulsion terpolymerization

This paper presents the use of soap-free emulsion terpolymerization to obtainphotonic crystals (PCs). Monodisperse latexes resulted from the polymerization of styrene (ST) with 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) at different compositions defined as system A, B and C respectively. The water solubility of the macroradicals determined different nucleation mechanisms in all three cases. The micellar nucleation mechanism was more predominant for generating system A, whereas the homogeneous nucleation was specific for system C. For system B, both nucleation mechanisms werepossible with the same probability. The latexes and the resulted PCs were characterized by optical microscopy (OM), dynamic light scattering (DLS), gel permeation chromatography (GPC) and UV-VIS spectroscopy.      

Solvent-free mechanochemical chlorination of hydrocarbons with CuCl2

Solvent-free chlorination of biphenyl and naphthalene was performed under mechanochemical stressing by high-energy ball milling (HEM) of a mixture of CuCl₂ (95 wt %) and the hydrocarbon (5 wt %). The reactivity of the selected hydrocarbons towards CuCl₂ during HEM partially correlates with their ionisation potentials (IP): hexadecane (9.91 eV) > biphenyl (8.27 eV) > naphthalene (8.14 eV).     

A new fluorescent double-cavity calix[4]arene: synthesis and complexation studies toward nitroanilines

A novel bicyclic calix[4]arene (4) molecular receptor has been synthesized, and its sensory abilities toward noxious aromatic nitroamines evaluated in apolar media. Molecular host–guest interactions examined through fluorescence and ¹H NMR spectroscopies showed the formation of 1:1 type endo-inclusion complexes with all the nitroaniline guests. The potential of 4 as a chemical sensor is established.     

THE CHEMISTRY OF (ECN)2 (E = S,Se) AND RELATED COMPOUNDS

The psuedohalogens (ECN)₂ (E = S, Se) have been prepared by reaction of AgNCS with bromine and AgNCSe with iodine respectively. (SCN)₂ spontaneously polymerises to give polythiocyanogen a polymer of unknown structure with empirical formula (SCN)_x. A series of late transition metal complexes bearing the ambidentate psuedohalide ligands (ECN) (E = S, Se) have been synthesised. In addition we have prepared a series of late transition metal complexes of the cyanodithioimidocarbonate ion [C₂N₂S₂]^2? and the first transition metal complexes of the cyanodiselenocarbonate ion [C₂N₂Se₂]^2?.     

C-Phosphorylation of Electron-Rich Heterocycles by Trivalent Phosphorus Halides

Abstract

Convenient methods for introducing dihalogenphosphinogroup at of pyrrole and hran rings have been developed. It was found that dibromphosphinogroup migrated from the second to the third position of the N-methylpyrrole. Convenient methods for phosphorylation of N- alkylcarbazole and iminostilbene have been developed.