Effects of quaternary ammonium bases on valence-saturated but coordination-unsaturated chelates: Part IV. Extraction of some divalent metal 8-hydroxyquinolinates

The effect of zephiramine on the chelate formation and extraction of some divalent metals with oxine is reported. In the presence of zephiramine, the non-extractable 1:2 zinc— and cadmium—oxine chelates as well as the extractable 1:2 nickel— and manganese—oxine chelates become highly coordinated ternary complexes, M(Q)₃ (zeph), which are easily extracted into 1,2-dichloroethane. Copper is easily extracted into 1,2-dichloroethane as Cu(Q)₂, which is not affected by zephiramine.     

n-Butyllithium-promoted regioselective elimination of vicinal bis-triflate having an adjacent ether oxygen

Regioselective elimination of a vicinal bis-triflate having an adjacent ether oxygen functional group has been developed. Considered in the context of our studies of the regioselective elimination of vicinal dibromide, the key to the mechanism involves the electron-withdrawing inductive effect of the neighboring oxygen functional group. Aliphatic vinyl triflate was shown to be effective in Suzuki–Miyaura cross coupling compared with corresponding aliphatic vinyl bromide.     

Low-temperature synthetic route based on the amorphous nature of giant species for preparation of lower valence oxides

We examined low-temperature synthetic route based on the amorphous nature of giant species to succeed to prepare Cs blue bronze (Cs_0.3MoO₃), which has never obtained by usual high-temperature methods, at ca. 680 K. Solid solutions (K_1−xRb_x)_0.28MoO₃ and (Li_1−xNa_x)_0.9Mo₆O₁₇ were also obtained at lower temperatures (ca. 670 K). For the latter system consisting of non-isostructural end members, Li_0.9Mo₆O₁₇-structure type solid solution was formed even when 0.25<x<0.70, unlike the case by the usual high-temperature methods. Metastable mixed oxides Ln₂Mo₃O₉ (Ln=La, Gd) were obtained, but not as single phases.     

General route to 2-alkyl-2-butenolactones via the retro-Diels-Alder reaction

Various 2-alkyl-2-butenolactones were simply prepared from cyclopentadiene-maleic anhydride adducts through the retro-Diels-Alder reaction. The procedure was applied for the synthesis of dehydrolappaol A dimethyl ether.     

Synthetic Studies of N‐demethylossamine and Elaboration of its Glycosylation

An amino‐sugar, N‐demethylossamine, was efficiently synthesized from D‐threonine, two stereogenic centers of which were directly used as those at the C‐4 and 5 positions of the target sugar. In addition, the glycosylation study indicated that reaction of the acetate 7 with cyclopentanol under Lewis acid conditions, provided the desired α‐L‐glycoside 9α.      

C2-substituted 8-aza-7-deaza-2′-deoxyadenosines as environmentally sensitive fluorescent nucleosides for discriminating apurinic/apyrimidinic sites in DNA duplex

We synthesized various C2-naphthylethynylated 8-aza-7-deaza-2′-deoxyadenosines 1a–1c as novel environmentally sensitive fluorescent (ESF) purine nucleosides. In particular, the N,N-dimethylamino-substituted derivative 1c exhibits a remarkably high solvatochromicity (Δ$\mathrm{\lambda }$ = 111 nm). 1c-containing oligodeoxynucleotide (ODN) probes clearly discriminated an apurinic/apyrimidinic site (AP site) in the complementary strand via a change in emission wavelength and intensity when hybridized with a target ODN.     

Electric polarization memory effect in a magnetoelectric multiferroic CuFe1−xGaxO2

Magnetic oxide CuFeO₂ is a magnetoelectric multiferroic with new type of spin–polarization coupling different from that in the spin-current mechanism, where magnetic field-induced or nonmagnetic impurity-induced proper helical magnetic ordering generates a spontaneous electric polarization parallel to the helical axis. Using a CuFe_1−xGa_xO₂ sample with x=0.035, in which the single ferroelectric phase is realized below T_N8 K in zero magnetic field unlike CuFe_1−xAl_xO₂, we have performed pyroelectric current, thermally stimulated current (TSC) and polarized neutron diffraction measurements to study a memory effect that the electric polarization is partially preserved even for 2nd-cooling from above T_N without poling electric field. It was found that the charge trapped during 1st-cooling with poling electric field, which is released as TSC on heating, plays an important role in the memory effect.     

DBU-promoted regioselective HBr-elimination of vicinal dibromides: effects of the adjacent oxygen and/or other heterofunctional groups

DBU-promoted HBr-eliminations of a variety of vicinal dibromides having an adjacent heteroatom (F, O, or N) under mild basic conditions and relevant theoretical calculations were carried out. These HBr-eliminations proceeded more or less regioselectively, and all associated calculation results agreed with the experimental facts. This work suggests that the HBr-elimination selectivity is an effect of the electronegativity of the neighboring heteroatoms themselves rather than the electron-withdrawing effects of the entire heterofunctional group.     

A precise spectrophotometric determination of a major constituent in pure materials: Application to pure magnesium metal

A spectrophotometric method is proposed for the direct assay of pure materials. The bulk of the metal to be determined is reacted with an accurately measured amount of a chelating agent, and the small excess of metal ion is determined spectrophotometrically with a chromogenic reagent. The optimal conditions can be predicted by drawing the theoretical spectrophotometric titration curves near the equivalent point of a supposed titration with the chelating agent as titrant and the chromogenic reagent as indicator. The method was applied to pure magnesium metal with EDTA as the chelating agent and calmagite as the chromogenic reagent, and the relative standard deviation was found to be 0.014%. The accuracy and precision appear to be much better than those attainable by titrimetry or differential spectrophotometry.