Structural characterization of some substituted azolidine molecules: UPS photoelectron spectroscopic studies

The He(I) photoelectron spectra of some heterocyclic penta-atomic rings containing carboamido, thiocarbamido or selenocarbamido groups are reported. Ab initio and CNDO/2 computational methods have been used to assign the first four ionized molecular orbitals, by comparison with previously studied related molecules. Structural effects in homologous series of compounds, particularly conjugation between N and the CY (Y = O, S, Se) moiety, and the through-space interaction between ring heteroatoms are analysed.     

Difluoroacetaldehyde N-Triftosylhydrazone (DFHZ-Tfs) as a Bench-Stable Crystalline Diazo Surrogate for Diazoacetaldehyde and Difluorodiazoethane

Despite the growing importance of volatile functionalized diazoalkanes in organic synthesis, their safe generation and utilization remain a formidable challenge because of their difficult handling along with storage and security issues. In this study, we developed a bench-stable difluoroacetaldehyde N-triftosylhydrazone (DFHZ-Tfs) as an operationally safe diazo surrogate that can release in situ two low-molecular-weight diazoalkanes, diazoacetaldehyde (CHOCHN₂) or difluorodiazoethane (CF₂HCHN₂), in a controlled fashion under specific conditions. DFHZ-Tfs has been successfully employed in the Fe-catalyzed cyclopropanation and Doyle–Kirmse reactions, thus highlighting the synthetic utility of DFHZ-Tfs in the efficient construction of molecule frameworks containing CHO or CF₂H groups. Moreover, the reaction mechanism for the generation of CHOCHN₂ from CF₂HCHN₂ was elucidated by density functional theory (DFT) calculations.     

Highly Ordered TiO2 Nanotubes for Electrochemical Sensing of Hair Dye Basic Brown 17

Self‐organized Ti/TiO₂ nanotubular array electrodes were prepared by electrochemical anodization and used to monitor the reduction of the hair dye basic brown 17 (BB17) at a potential of ?0.60 V vs. Ag/AgCl. Analytical curves were obtained from 1.0×10^?6 to 8.0×10^?5 mol L^?1 with a detection limit of 1.3×10^?7 mol L^?1 by using the best experimental conditions, linear scan voltammetry at pH 6, scan rate=60 mV s^?1, and accumulation time=5 min. The detection system performance was not interfered by other hair dyes and successfully used to determine the dye in tap water samples.     

First total synthesis of labeled EPA and DHA-derived A-type cyclopentenone isoprostanoids: [D2]-15-A3t-IsoP and [D2]-17-A4t-NeuroP

A-type cyclopentenone isoprostanoids are abundantly formed in vivo by radical peroxidation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are consumed daily for the prevention of cardiovascular and neurological pathologies. To facilitate in depth studies concerning the effects of these oxidized isoprostanoids on human health, labeled derivatives are necessary. In this paper, we have accomplished the first total synthesis of labeled A-type cyclopentenone isoprostanoids, namely 17,18-[D₂]-15-A_3t-IsoP and 19,20-[D₂]-17-A_4t-NeuroP. The two enantioselective routes are highly convergent, stemming from a common intermediate, readily available by a Julia–Kocienski reaction, and feature the semihydrogenation of an alkyne moiety for the installation of the labeled lower side chain.     

Physicochemical study of spiropyran-terthiophene derivatives: photochemistry and thermodynamics

The photochemistry and thermodynamics of two terthiophene (TTh) derivatives bearing benzospiropyran (BSP) moieties, 1-(3,3″-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4″-didecyloxy-2,2':5',2″-terthiophene-3'-acetate (BSP-2) and 1-(3,3″-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4″-didecyloxy-2,2':5',2″-terthiophene-3'-carboxylate (BSP-3), differing only by a single methylene spacer unit, have been studied. The kinetics of photogeneration of the equivalent merocyanine (MC) isomers (MC-2 and MC-3, respectively), the isomerisation properties of MC-2 and MC-3, and the thermodynamic parameters have been studied in acetonitrile, and compared to the parent, non-TTh-functionalised, benzospiropyran derivative, BSP-1. Despite the close structural similarity of BSP-2 and BSP-3, their physicochemical properties were found to differ significantly; examples include activation energies (E(a(MC-2)) = 75.05 kJ mol(-1), E(a(MC-3)) = 100.39 kJ mol(-1)) and entropies of activation (ΔS = 43.38 J K(-1) mol(-1), ΔS = 37.78 J K(-1) mol(-1)) for the thermal relaxation from MC to BSP, with the MC-3 value much closer to the unmodified MC-1 value (46.48 J K(-1) mol(-1)) for this latter quantity. The thermal relaxation kinetics and solvatochromic behaviour of the derivatives in a range of solvents of differing polarity (ethanol, dichloromethane, acetone, toluene and diethyl ether) are also presented. Differences in the estimated values of these thermodynamic and kinetic parameters are discussed with reference to the molecular structure of the derivatives.     

One-pot consecutive reactions based on the synthesis of conjugated enones by the re-catalysed meyer-schuster rearrangement

Re catalysis in one-pot reactions: An atom-economical, one-pot strategy that involves alkyne deprotonation and a subsequent rhenium(V)-catalysed Meyer-Schuster rearrangement of the alkynol to provide α,?-unsaturated enones in high yield has been developed. Subsequent in situ hydride reduction or Diels-Alder reaction of the enones provided products in good-to-high overall yields.     

Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co_1.1−x Zn _x Ge_0.1Fe_1.2O₁ spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co²⁺ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.