Microwave-assisted Claisen Rearrangement of 1-Allyloxy-4-hydroxybenzene in the Presence of Metal Salt

: Microwave-assisted Claisen rearrangement of allyloxybenzene with a hydroxyl group was conducted in the presence of metal salts. The rearrangement was promoted in the presence of an alkali metal salt, because the reaction substrate was converted to a phenoxide-type ion, which can efficiently absorb microwaves. In contrast, a Lewis acid was strongly coordinated to the ethereal oxygen, and this structure could also absorb microwaves efficiently.

Cs2CO3 as a source of carbonyl and ethereal oxygen in a Cu-catalysed cascade synthesis of benzofuran [3,2-c] quinolin-6[5-H]ones

Simultaneous construction of C–C, C–O, and C–N bonds utilizing Cs2CO3 as a source of carbonyl (CO) and ethereal oxygen and a cascade synthesis of benzofuro[3,2-c]quinolin-6(5H)-one are achieved using a combination of Cu(OAc)2 and Ag2CO3.

Synthesis, crystal structure and properties of [Co(L)2](ClO4)2 (L=1,3-bis(1H-benzimidazol-2-yl)-2-oxapropane)

The reaction of 1,3-bis(1H-benzimidazol-2-yl)-2-oxapropane (L) with Co(ClO4)2?6H2O in absolute ethanol produces di[1,3-bis(1H-benzimidazol-2-yl)-2-oxapropane-k2N,N?]cobalt(II)diperchlorate chelate complex ([Co(L)2](ClO4)2, 1). The complex 1 was characterized by elemental analysis, magnetic moment, molar conductivity, thermogravimetric analysis, FT-IR, UV-visible, mass spectrometry, and its solid state structure was determined by single crystal X-ray diffraction. According to the thermogravimetric analysis data, there is no any water coordinated or uncoordinated in 1 as well as elemental analysis. The complex 1 has 1:2 M:L ionic characteristic according to the molar conductivity. In the complex, the distances between the cobalt and the ethereal oxygen atoms (Co1-O2: 2.805(3); Co2-O1: 2.752(2) ?) show the semi-coordination bonding and the Co(II) ion is six-coordinated with a N4O2 ligand set, resulting in a distorted octahedron.

Comparison of Water Adsorption Characteristics of Oligo and Polysaccharides of α-Glucose Studied by Near Infrared Spectroscopy

The adsorption properties of water molecules on oligo and polysaccharides are attributed to the OH groups of the glucose rings in the molecules. The water molecules are adsorbed onto OH groups by hydrogen bond formation. Near infrared spectroscopic and gravimetric techniques were used in analysing the adsorption characteristics of malto-oligosaccharides and some polysaccharides. Near infrared spectra of the dry oligo and polysaccharides were acquired during the adsorption of water molecules at a relative humidity of 50-55%. The amounts of water adsorbed by the samples were also recorded by an analytical balance. Second derivative techniques were used in decomposing the OH combination frequencies of the adsorbed water molecules in the region 5300-5000 cm -1.The results indicate that the water molecules are adsorbed on to C2 and C3-OH groups at a higher rate compared to the adsorption onto C1-OH groups in the molecules. Adsorption also takes place onto the ethereal oxygen atoms in the glucose rings in malto-oligosaccarides. The gravimetric results show that the adsorption of water molecules increases with the number of glucose units in the malto-oligosaccharides except maltotriose which has the highest adsorption over a period of 75 minutes. Furthermore, the adsorption characteristics of amylose and amylopectin are similar.

Chemical Basis for High Activity in Oxygenation of Cyclohexane Catalyzed by Dinuclear Iron(III) Complexes with Ethereal Oxygen Containing Ligand and Hydrogen Peroxide System

The crystal structures of two binuclear iron(III) complexes with linear μ-oxo bridge, Fe2OCl2 (tfpy)2 (ClO4)2 ·2CH3CN and Fe2OCl2(epy)2(ClO4)2 were determined, where (tfpy) and (epy) represent N,N-bis(2-pyridylmethyl)-tetrahydrofurfurylamine and N,N-bis(2-pyridylmethyl)-2-ethoxyethylamine, respectively. Their structural features are essentially the same as that of the corresponding linear binuclear complex with (tpa)-complex, Fe2OCl2(tpa)2(ClO4)2, where (tpa) is tris(2-pyridylmethyl)amine; the ligands (tfpy) and (epy) act as a tetradentate tripod-like ligand, and Fe-O (ethereal oxygen atom; these are located at the trans-position of bridging oxo-oxygen atom) distances are 2.209(4) and 2.264(2) Å for (tfpy) and (epy) compounds, respectively. These two (tfpy) and (epy) complexes exhibited much higher activity for the oxygenation of cyclohexane in the presence of hydrogen peroxide than that of the (tpa) complex. In contrast to this, the former two complexes exhibit negligible activity for the decomposition of hydrogen peroxide, whereas the catalase-like function of the (tpa) compound is remarkable. These are indicating that an active species for oxygenation of cyclohexane, which is assumed to be an iron(III)-hydroperoxide adduct with η1-coordina­tion mode, should be different from that is operating for decomposition of hydrogen perox­ide; for the latter case formation of a (μ-η1:η1-peroxo)diiron(III) species being stressed. The EHMO calculation showed that electronic interaction between the monodentate hydroperox­ide adduct of the binuclear iron(IIl)-(tfpy) compound and the tetrahydrofuran ring of the ligand system may lead to facile peroxide-tetrahydrofuran linkage formation, and the interac­tion described above should promote the O-O cleavage of the peroxide ion heterolytically. Based on these discussions, it was concluded that heterolytic O-O bond cleavage of the iron(III)-hydroperoxide adduct caused by electronic interaction with organic moiety contain­ing an ethereal-oxygen and by approach of the substrate which donates electron to the perox­ide adduct should play an important role in producing a high-valent iron-oxo species in these systems. In the case of (tpa) complex, formation of a hydroperoxide adduct linking with the ligand system seems to be unfavorable because of both the steric and electronic reasons.