Heteroatom Chemistry最新文献

Multidefence antioxidants represent a valuable solution for the protection against oxidative stress. From the planned synthesis of a catechol-tocopherol hybrid, we isolated a catechol-hydroquinone hybrid through a BBr₃-mediated benzochromene-fluoren-1-ol transposition. The compound prepared showed a remarkable chain-breaking antioxidant in the catechol portion, while the very sensitive hydroquinone moiety revealed to be an efficient generator of hydroperoxyl radicals.

Iron complex-catalyzed dehydrogenative Sn–E (E = S, Se) bond formation of hydrostannane with thiol and selenol was achieved. All new compounds were fully characterized using ¹H, ¹³C{¹H}, ⁷⁷Se{¹H}, and ¹¹⁹Sn{¹H} NMR measurements and elemental analyses. The structure of 1,1′-(1,3-dithia-2,2-dibutylstanyl)-[3]ferrocenophane was confirmed by single-crystal X-ray diffraction.

The self-assembly of sulfur-containing heterocyclic compounds, 5,6,11,12,17,18-hexathia-5,6,11,12,17,18-hexahydrotrinaphthylene and 5,7,12,14-tetrathiapentacene having octyloxy groups 1 and 2, was examined. Sulfides 1 and 2 self-assembled to form fibrous materials. The methylation reactions of 1 and 2 proceeded to give monomethylated sulfonium salts 3 and 4, and the self-assembly of 3 and 4 was also studied. Fibrous materials of sulfonium salts 3 and 4 were formed in hexane/CHCl₃ solution. The structure of the fibrous material of 3 might be similar to that of the fibrous material of 1. The aggregation behavior of 1 and 3 in cyclohexane-d₁₂ was studied by VT ¹H NMR measurements at various concentrations. VT ¹H NMR measurements revealed that the stacking structure of 1 was different from that of 3.

In an experimental and statistical study, the effects of five synthesis parameters on the degree of order of nano-sized Al-MCM-41 were basically investigated. In a series of designed experiments, hydrothermal conditions (temperature and time), Si/Al, NaOH/Si, and cetyltrimethylammonium bromide/Si molar ratios were studied each at three levels. Degree of order of mesoporous channels was evaluated using small angle XRD. Nitrogen adsorption-desorption technique, scanning and transmission electron microscopy (SEM-TEM), and field-emission SEM were also applied to detect the textural properties and the morphology of prepared nanoparticles. Energy-dispersive X-ray spectroscopy and mapping (EDS-Map), inductively coupled plasma-optical emission spectroscopy, and small angle X-ray scattering were provided as complementary analyses. An accurate reduced quadratic equation was proposed as a function of effective terms in good agreement with the experimental results. Based on the analysis of variance, the amount of aluminum incorporated, sodium hydroxide, and the hydrothermal treatment duration was found to possess more dramatic effects on the degree of order than the other factors. The optimum conditions for the synthesis of a well-ordered Al-MCM-41 were also obtained with the lowest template and the minimum hydrothermal duration verified by two validation tests.

1-Aminopyrimidine-2-one derivatives (1a-c) were prepared in two steps from furan-2,3-diones and semicarbazones in toluene/benzene. Pyrimidin-[1(2H)-yl] acetamide derivatives and isophthalimide derivatives were synthesized from the nucleophilic acyl substitution reactions of compounds 1a-c with chloroacetyl chloride. The structures of compounds 2a-f were verified by IR, ¹H NMR, ¹³C NMR and elemental analyses. The obtained final organic compounds were tested as catalysts in the Mizoroki-Heck coupling reaction. They mostly exhibited very high catalytic activity results for the coupling reaction of styrene with different aryl bromide derivatives.

A series of tris[2-(4′-substituted butoxyphenyl)]phosphine oxides [2-X(CH₂)₄OC₆H₄]₃PO (X = OAc (2), OH (3), OSO₂Me (4), Br (5), and N₃ (6)) useful as precursors of new tripodal ligands have been prepared. Alkylation of initial tris(2-hydroxyphenyl)phosphine oxide (1) resulted in triacetate 2, which was deprotected to triol 3. The latter has been converted into trimesylate 4, which has been treated with LiBr or NaN₃ to give the corresponding tribromo or triazido derivatives 5 and 6, respectively. According to X-ray diffraction, the molecules of compounds 2, 5, and 6 in crystal adopt conformation where two side arms are oriented to the same direction as the P=O group, while the third side arm is oriented in the opposite manner.

The synthesis, aromaticity, and optical and electrochemical properties of zinc(II) complexes of 10,15,20-triaryl-15-aza-5-oxaporphyrin (TriAAOP) were investigated. Metal-templated cyclization of a zinc(II) 1,19-dichloro-5,10,15-triaryl-10-azatetrapyrrin complex with an oxygen source afforded 20π TriAAOP in the neutral form. Oxidation of 20π TriAAOP with silver (I) hexafluorophosphate generated the 19π radical cation or 18π dication depending on the content of oxidant used. The interconversion between the three oxidation states (18π, 19π, and 20π) resulted in distinct changes in the aromaticity and optical properties of the 15-aza-5-oxaporphyrin π-system. Nuclear magnetic resonance spectroscopy of 20π TriAAOP revealed its antiaromatic character, whereas that of the 18π TriAAOP dication showed its aromatic character. The combined effect of the two meso-heteroatoms was directly reflected in the redox properties of the porphyrin ring; TriAAOP was reduced more easily and more difficult to oxidize than the zinc(II) complex of 5,10,15,20-tetraaryl-5,15-diaz-aporphyrin (TADAP). In the ultraviolet-visible-near–infrared spectra of the materials, the lowest-energy electronic excitations of the 19π and 18π TriAAOP derivatives were considerably red-shifted compared with those of the isoelectronic TADAP derivatives. Based on the results of density functional theory calculations, it was concluded that the observed differences between TriAAOP and TADAP would arise from the high electronegativity of oxygen; specific frontier orbitals of the TriAAOP π-systems were energetically stabilized relative to those of the TADAP π-system. The present findings corroborate that the meso-modification of a porphyrin rings with different kinds of heteroatoms is a promising strategy to fine tune their light-response properties that are switchable by reversible single electron transfer processes.

Stable conjugated oligomer dications 1²⁺ and 2²⁺ composed of 2,5-di(2-thienyl)-N-methylpyrrole (DTP) units at the both ends of the π-systems with methoxy substituents at the 3-position of thienyl units and methylthio end-capping group and benzo[2,1-b:3,4-b′]dithiophene (BDT) unit(s) at the central part with sterically demanding phenyl substituents were synthesized. From DFT calculations and ESR experiments, it was concluded that the diradical character in 1²⁺ and 2²⁺ was reduced in comparison with the radical character of their reference compound 3^·+ composed of one DTP and one BDT units. In addition, the shorter 1²⁺ was considered to have a further lower diradical character than that of 2²⁺. Nevertheless, judging from the results of VT-UV-vis-NIR measurements, both 1²⁺ and 2²⁺ showed a comparable π-dimerization ability at the DTP moiety in dichloromethane solution with 3^·+.

New activated indolylpyrrolidones—their methylthiopyrrolinium salts—in the reactions with several CH-acids were studied. 2-Nitromethylene- and 2-dicyanomethyleneindolylpyrrolidines were obtained from 5-indolyl-2-methylthiopyrrolinium salts with good yields. The reduction in these nitro compounds yields the respective aminomethylpyrolidines. The rigid structure of the starting compounds has significant stereoelectronic requirements of nucleophilic agents.

We have designed and synthesized tetraferrocenyloligothiophenes, namely, 4,4′5,5′-tetraferrocenyl-2,2′-bithiophene (TFBT) and 4,4″,5,5″-tetraferrocenyl-2,2′:5′,2″-terthiophene (TFTT). By using an electrochemical technique, we revealed that tetraferrocenyloligothiophenes show multi-redox reactions derived from four ferrocene fragments and one α-oligothiophene spacer, and a number of the thiophene rings in the α-oligothiophene spacer can be attuned to the redox potentials and the multiple electron transfer process. Consequently, we have succeeded in the construction of different types of multi-step multi-electron redox systems by constructing four organometallic redox-active ferrocenes and one organic redox-active α-oligothiophene differing in the number of thiophene rings.