Radical cation of dibenzothiophene fully annelated with bicyclo[2.2.2]octene units: X-ray crystal structure and electronic properties

New dibenzothiophene 2 fully annelated with bicyclo[2.2.2]octene units was synthesized and oxidized to stable radical cation salt 2(*+)SbCl(6)(-), whose structure was determined by X-ray crystallography. Although the intrinsic electronic structure of 2(*+) is predicted to be close to structure A, an interaction with the counteranion makes structure B contribute significantly. A part of the salt 2(*+)SbCl(6)(-) underwent rearrangement to arenium ion 6(+), whose structure was also clarified by X-ray crystallography.     

Theoretical modeling of photo-induced wave propagation in liquid-crystalline Langmuir monolayers

A phenomenological model of wave propagation in photo-excited liquid-crystalline Langmuir monolayers is constructed. The spontaneous splay deformation of the liquid-crystalline order and the anisotropy of photo-excitation of molecules are taken into account in this model. Numerical simulations of the model well reproduce qualitative features of the wave propagation phenomenon observed in recent experiments. A linear stability analysis of the model equations reveals that an interplay between the spontaneous splay deformation and the anisotropy of the photo-excitation can lead to the wave propagation.     

Cobalt-carbene complex with single-bond character: intermediate for the cobalt complex-catalyzed cyclopropanation

It is generally considered that metal-carbene carbon bonds in carbene complexes for cyclopropanation should be double-bonded; however, the theoretical and FT-IR analyses revealed that the cobalt-carbene carbon bond of the 3-oxobutylideneaminato or the salen-cobalt-carbene complexes was characterized as a single bond.     

Separation of zinc compounds by sequential metal vapor elution analysis with atomic absorption detection

The separation of zinc compounds, containing zinc chloride, nitrate, and sulfate, at low concentrations by sequential metal vapor elution analysis (SMVEA) with argon carrier gas was reported. A molybdenum column, inserted with a tungsten wire, was developed for the separation of zinc compounds by SMVEA. The optimum separation conditions were a vaporization temperature of 1370 K, a column temperature of 1350 K, and a carrier gas flow rate of 2.5 mL min⁻¹. Under the optimized experimental conditions, the zinc compounds could be roughly separated by SMVEA, although a part of peak profiles overlapped. The number of theoretical plates was 36 for ZnCl₂, 62 for Zn(NO₃)₂, and 80 for ZnSO₄ in the SMVEA column. The present SMVEA system may be able to be applied widely to various analytical instruments.     

Synthesis of Oligo(thienylfuran)s with Thiophene Rings at Both Ends and Their Structural,Electronic, and Field‐Effect Properties

Oligo(thienylfuran)s with thiophene rings at both ends ( SOSOSOS , DE‐SOSOS , DH‐SOSOS , DE‐SOSOSOS , and DH‐SOSOSOS ; S and O denote thiophene and furan rings, respectively, DE and DH denote diethyl‐ and dihexyl‐substituted, respectively) were newly synthesized by repetitive Stille coupling reactions. The UV/Vis maximum absorptions of the oligomers, SO , SOSO , SOSOS , SOSOSO , and SOSOSOS , exhibited a clear bathochromic shift with increasing number of heterocycles. The value of the oxidation peak potential (E_pa¹) determined by cyclic voltammetry decreased with an increase in the number of heterocycles by 0.06–0.08 V per heterocycle. The crystal‐packing structures of DE‐SOSOS and DH‐SOSOS determined by X‐ray crystallography have a herringbone motif and are denser than the reported structures of pentacene and α‐sexithiophene. The morphologies of thin films prepared by vacuum deposition and spin coating were investigated by atomic force microscopy and X‐ray diffraction. Among these films, those of DE‐SOSOS and DH‐SOSOS exhibited highly ordered arrangements. The devices based on vacuum‐deposited and spin‐coated films of DE‐SOSOS and DH‐SOSOS displayed the highest FET mobilities of 10^?2–10^?3 cm² V^?1 s^?1 among the oligomers reported in this study.     

Dependence of chiral recognition on the degree of substitution of cellulose benzoate

A series of cellulose benzoates with different degrees of substitution (DS) were prepared by aminolysis under homogeneous conditions. Using them as a stationary phase, the dependence of the chromatographic chiral recognition of cellulose benzoate (CB) on its DS was studied under normal phase conditions. For most enantiomeric pairs, chiral recognition decreased along with the decrease in DS. However, some enantiomeric pairs were resolved only by CBs carrying unsubstituted hydroxyl groups. Many of the compounds were quite strongly retained by cellulose benzoate with a DS of 2.8. A study of the retention behaviors of simple achiral compounds led us to the conclusion that the change in the retention behaviors by introducing free hydroxyl groups into tribenzoate is not caused by hydrogen bonding including the hydroxyl groups, but by a specific unidentified change.     

Development of a Divergent Synthetic Route to the Erythrina Alkaloids: Asymmetric Syntheses of 8‐Oxo‐erythrinine,Crystamidine, 8‐Oxo‐erythraline,and Erythraline

A general synthetic methodology toward the erythrina alkaloids has been developed. Inspired by a proposed biosynthetic mechanism, the medium‐sized chiral biaryl lactam was asymmetrically transformed into the common core A–D rings by a stereospecific singlet oxygen oxidation of the phenol moiety, followed by a transannular aza‐Michael reaction to the dienone functionality. The late‐stage manipulation of the oxidation and oxygenation states of the functional groups on the peripheral moieties enabled the flexible syntheses of the erythrina alkaloids.     

A Short,Efficient Synthesis of the Octamannan Residue of High Mannose Type Sugar Chains

Abstract

An efficient route for the synthesis of octamannan 1, found in high mannose type sugar chains, is described. to construct octasaccharide 1 by as few synthetic steps as possible, we employed a chemoenzymatic strategy: the enzymatic synthesis of oligosaccharide blocks using glycosidases followed by chemical coupling to form a branched structure. By use of this methodology, many synthetic steps were eliminated and 1 was easily synthesized.