Construction of Biaryls from Aryl Sulfoxides and Anilines by Means of a Sigmatropic Rearrangement

An unprecedented S−N variant of the benzidine rearrangement for construction of biaryls has been developed. Aryl sulfoxides underwent dehydrogenative coupling with anilines by successive treatment with trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid to provide the corresponding 2-amino-2′-sulfanyl- and/or 4-amino-4′-sulfanylbiphenyls. Mechanistic studies indicate that the C−C-bond-forming sigmatropic rearrangement proceeds intramolecularly from dicationic S−N-tethered species.     

Preparation of melt-textured NdBa2Cu3Oy bulk with Nd4Ba2Cu2O10 addition

The NdBa₂Cu₃O_y (Nd123) bulk superconductor, to which Nd₄Ba₂Cu₂O₁₀ (Nd422) particles were intentionally added, was prepared through the so-called MMTG process in Ar (99% purity) flowing atmosphere at an ambient pressure. The quasi-single crystal thus grown was about 1 cm × 1 cm × 1 cm in dimension. It turned out that the Nd422 particles were uniformly distributed in the Nd123-phase matrix in a fashion similar to the distribution of the intentionally added Y211 particles in the Y123 phase matrix. The superconducting transition temperature T_c for the sample subjected to post-annealing in oxygen atmosphere was 94 K. The critical current density J_c was determined to be 45 000 A/cm² at 77 K and 1 T, when the field was applied parallel to the c-axis of the sample. To the best of our knowledge, the J_c value is the highest and the size of the quasi-single crystal is the largest in the melt-textured Nd123 bulk superconductors so far reported.     

Tetrakis(alkylthio)thieno[3,4-c]thiophene: Synthesis,stability, and reactivity

The synthesis of tetrakis(alkylthio)thieno[3,4-c]thiophenes la-e by the dimerization reaction of bis(alkylthio)cyclopropenethiones is described. The remarkable thermodynamic and kinetic stability suggests the significant electron-accepting conjugation of the alkylthio substituents to the carbanionic 1, 3, 4, and 6 carbons in the framework. The isopropylthio- and ethylthio-substituted thienothiophenes 1d and 1e undergo cycloaddition reactions with dienophiles such as N-phenylmaleimide and dimethyl acetylenedicarboxylate to give the cycloadducts in moderate yields.     

Synthesis and properties of polyurethanes derived from bis-N-hydroxyimides and diisocyanates

Polyurethanes were synthesized by polyaddition reaction of bis-N-hydroxyimides and diisocyanates. The reactions were carried out in an aprotic polar solvent such as dimethylacetamide or N-methyl-2-pyrrolidone, and the polymers with inherent viscosities of up to 1.32 dl/g were obtained. These polyurethanes were found to exhibit high reactivity toward nucleophiles such as water and amines, which brought about rapid reduction of viscosity. The stabilities against heat and exposure to sunlight were also studied.     

The First Heterotriquinone and Dicyanoheterotriquinone Methide That Undergo a Five-Stage Amphoteric Redox Reaction

The dicyanomethylene group and not the quinone oxygen atoms is the site of the first one-electron reduction for the dicyanohetereotriquinone methide 1 , although the dicyanomethylene group is substituted at a cyclopentadienyl-like five-membered ring! Compound 1 is amphoteric and undergoes a five-stage sequence of one-electron redox reactions.     

Asymmetric synthesis catalyzed by chiral ferrocenylphosphine-transition metal complexes VII. New chiral ferrocenylphosphines with C2 symmetry

A new chiral ferrocenylphosphine ligand, 2,2′-bis[1-N,N-dimethylamino)ethyl]-1,1′-bis(diphenylphosphino)ferrocene (2), which has C₂ symmetry and a functional group on the side chain, was prepared by ortho-lithiation and phosphination of 1,1′-bis[1-N,N-dimethylamino)ethyl]ferrocene followed by optical resolution; recrystallization of the diammonium salt with tartaric acid. An X-ray diffraction study of PdCl₂[(+)-2] showed that the complex has square-planar geometry with two cis chlorine and two phosphorus atoms and ligand (+)-2 has an (S) configuration on the 1-dimethylaminoethyl side chain and (R) ferrocene planar chirality.     

Synthesis of Novel Heteroquaterphenoquinones and Their Electrochemical, Structural, and Spectroscopic Characterization

Novel heteroquaterphenoquinones, 5,5'-bis(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-5,5'-dihydro-2,2'-bithienyl (3) and its 2,2'-biselenienyl (4), 2,2'-bifuryl (5), and 2,2'-bi-N-methylpyrrolyl (6) analogues, were synthesized by a stepwise cross-coupling reaction or by a more convenient one-pot oxidative homocoupling reaction of heterocycle-substituted phenols. Despite a highly conjugation-extended system, the quinones 3-6 are very stable in the solid state and in solution in common organic solvents. These quinones undergo a reversible one-stage, two-electron reduction up to dianions and a two-stage, one-electron oxidation reaction up to dications. The E(1)(red) of these quinones increases with the increase in the aromaticity of the incorporated heterocycles. The E(1)(ox) of these quinones appears to be specified by the ionization potential of the incorporated heterocycles. Thus, the N-methylquinone 6 exhibiting the lowest E(1)(ox) value exhibits the smallest E(1)(sum) among the quinones 3-6. The quinone 5 was revealed to exist in an unusual O-cis conformation in the solid state by X-ray crystallography, whereas the quinone 3 exists in an S-trans conformation in the solid state. The cis and trans isomers are interconvertible in solution in 3-5, whereas only N-trans isomer was detected for 6 in (1)H NMR spectroscopy. The quinones 3-6 exhibit a very intense absorption maximum in the near-infrared region of 662-827 nm. Of these, the maximum absorption wave length of 6 shifts to a more bathochromic region by 149-165 nm than those of 3-5. The quinones 3-6 can be used as dyestuffs in various fields for laser-driven high-density optical storage media.     

Synthesis, structure and physical properties of layered semiconductors MCuFCh (M=Sr, Eu, Ch=S, Se)

Effects of open shell cations on magnetic, optical and carrier transport properties were examined for layered wide bandgap semiconductors MCuFCh (M=Sr, Eu, Ch=S, Se). Single-phase MCuFCh powder and ceramic samples were synthesized by solid-state reactions. The crystal structures refined by the Rietveld analyzes revealed that all the materials have the space group P4/nmm, indicating that the samples have the same crystal structure as that of layered oxychalcogenides LaCuOCh, and cation vacancies of several percent were present for Cu⁺ and Eu²⁺ sites in EuCuFCh. Thermopower measurements revealed that both SrCuFCh and EuCuFCh were p-type semiconductors. Degenerate conduction was observed for EuCuFCh with conductivities >1 S cm⁻¹, whereas SrCuFCh exhibited thermally activated behavior. The optical band gaps of SrCuFS and SrCuFSe estimated were approximately 3.0 and 2.7 eV, respectively, and those of EuCuFCh were ∼2 eV. Temperature dependence of magnetic susceptibilities of EuCuFCh followed the Curie-Weiss law down to 5 K and the samples did not show any transition to a magnetic ordering phase.