Synthesis of optically active tetrahydrozerumbone

Tetrahydrozerumbone 2, which has a powerful balmy fragrance, has a stereogenic carbon at C2 and can be easily prepared from zerumbone 1, which is one of the most important materials that displays an NMRDOS character. Reduction of 2 gave two diastereomers 3 and 4; their optically active (>99% ee) alcohols were obtained by lipase-catalyzed stereoselective transesterification of each racemic alcohol. The enantioselectivity of tetrahydrozerumbol does not entirely depend on the hydroxyl position but on the 2-methyl position. Compounds (R)-2 and (S)-2 were obtained by Dess–Martin oxidation of the corresponding alcohols. Interestingly, (R)-2 showed a strong balmy fragrance while (S)-2 had hardly any fragrance.     

Formation of an Azaruthenacyclopentadiene Skeleton via Ammonia Activation by an Electron-Deficient Ru3 Cluster

A dicationic triruthenium complex containing a μ₃-η³-C₃ ring, [(Cp*Ru)₃(μ₃-η³-C₃MeH₂−)(μ₃-CH)(μ-H)]²⁺ ( 1 a , Cp*=η⁵-C₅Me₅), reacted with ammonia to yield a μ-amido complex, [(Cp*Ru)₃(μ₃-η³-CHCMeCH) (μ₃-CH)(μ-NH₂)]²⁺ ( 5 ), via N−H bond scission. Subsequent treatment with base resulted in C−N bond formation to yield a μ₃-η²:η²-1-azabutadien-4-yl complex, [(Cp*Ru)₃(μ₃-CH)(μ₃-η²:η²-NH=CH−CMe=CH−)]⁺ ( 6 a ). The azaruthenacyclopentadiene skeleton was alternatively synthesized by the photolysis of mono-cationic complex [(Cp*Ru)₃(μ₃-η³-C₃RH₂−)(μ₃-CH)]⁺ ( 2 a ; R=Me, 2 b ; R=H) in the presence of ammonia. The C₃ ring skeleton was broken via the electron transfer to the π*(C−C) orbital in the C₃ ring, and a transiently generated unsaturated μ₃-allylic species can take up ammonia, resulting in N−H bond scission followed by C−N bond formation.     

Palladium-catalyzed reaction of allyl carbamates; allylation of carbonucleophiles,and protection-deprotection of amines

Allylation of carbonucleophiles with allylic carbamates under neutral conditions has been studied. The C-allylation of carbonucleophile is competitive with the N-allylation of amines, and the structure of amines is crucial for the selectivity. Bulky secondary amines gave the best results. Also a new method of protection-deprotection of amines as carbamates has been developed. Smooth deprotection is possible by the palladium-catalyzed reaction of allyl carbamates with formic acid. This method is particulary useful for primary amines, including optically active amino acids.     

Effect of Substrates on the Addition Polymerization of 1,4-Benzenedithiol to 1,4-Diethynylbenzene in the Solid State and the Electronic Properties of the Resulting Polymer

The effect of substrates on the addition polymerization of 1,4-benzenedithiol (BDT) to 1,4-diethynylbenzene (DEB) in the solid state and the electronic properties of the polymers obtained were studied. As the substrate polymer sheets, for instance, PET (poly (ethylene terephthalate)) sheet, ON-6 (oriented nylon-6) sheet and so on having surface free energies Γ_s from 27.4 to 55.0 erg/cm² were used. At the monomer sublimation temperature of 60°C, the S wt% (sulfur content) and the cis content of the polymers were not affected by the kind of polymer sheets. However, the molecular weights, M¯_n of the polymers polymerized on the polymer sheets were 13,000–30,000, and the values were several times higher than the molecular weight of the polymers polymerized on glass plate. On the other hand, at the sublimation temperature of 82°C, the cis content of the polymers apparently increased with decreasing d-value of the polymer sheets. On X-ray diffraction patterns of monomer mixtures sublimed onto polymer sheets, the diffraction intensities and the diffraction peak positions were concerned with the d-value of the polymer sheets. Using polymer sheets, the diffraction peak intensities of the monomer mixture at 7.73 and 7.58 Å decreased compared with those on glass plate. In contrast, the peak at 3.65 Å, which is a negligibly small peak on glass plate, obviously increased. However, as the d-value of the polymer sheets (PET 3.45 Å; OPP (oriented polypropylene) 5.2 Å) increased, the diffraction peak intensities at 7.73 Å and 7.58 Å gradually increased and the diffraction peak intensity at 3.65 Å gradually decreased. The parallel electrical conductivities (σ_||) toward the layered structural polymer on PET, ON-6 and glass plate under air atmosphere were 10⁻⁷, 10⁻⁹ and 10⁻¹¹ S/cm, respectively. Under a reduced pressure of 10⁻³ mmHg, the σ_|| values of each polymer lowered by one or two orders of magnitude. On the other hand, the σ_|| values of the nonlayered structural polymers under air atmosphere were about 10⁻¹¹–10⁻¹² S/cm and were independent of the substrates. Even under a reduced pressure of 10⁻³ mmHg, the σ_|| values hardly changed and remained at 10⁻¹¹–10⁻¹² S/cm. The vertical electrical conductivities (σ_⟂) of the layered structural polymers on conductive PET sheet coated by indium tin oxide or NESA glass plates were independent of the substrates and were 10⁻¹⁴ S/cm under air atmosphere. The σ_⟂ values of the nonlayered structural polymers also exhibited the same values. The reversible change of the amount of the layered structural polymer on PET sheet was also caused by irradiation of the photo-light which is the effective wavelength for the phase transition of the polymers mounted on glass plate. The σ_|| value of the layered structural polymer on ON-6 sheet reversibly changed with the amount of the layer structure controlled by the photo-light, that is, the σ_|| increased up to about one order of magnitude by the photo-light at 545.6 nm. On the other hand, the _|| decreased to about one order of magnitude by the photo-light at 539.6 nm. Anisotropic conductivity with respect to σ_|| and σ_⟂, and oxygen doping mechanisms were discussed in relation to the layer structure of polymers. © 1997 John Wiley & Sons, Ltd.     

Efficient construction of the hexacyclic ring core of palau'amine: the pKa concept for proceeding with unfavorable equilibrium reactions

Palau''amine has received a great deal of attention as an attractive synthetic target due to its intriguing molecular architecture and significant immunosuppressive activity, and we achieved its total synthesis in 2015. However, the synthesized palau''amine has not been readily applicable to the mechanistic study of immunosuppressive activity, because it requires 45 longest linear steps from a commercially available compound. Here, we report the short-step construction of the ABCDEF hexacyclic ring core of palau''amine. The construction of the CDE tricyclic ring core in a single step is achieved by our pK_a concept for proceeding with unfavorable equilibrium reactions, and a palau''amine analog without the aminomethyl and chloride groups is synthesized in 20 longest linear steps from the same starting material. The palau''amine analog is confirmed to retain the immunosuppressive activity. The present synthetic approach for a palau''amine analog has the potential for use in the development of palau''amine probes for mechanistic elucidation.

A palau''amine analog (2) was synthesized from 2-cyclopentenone in 20 steps. The construction of the CDE tricyclic ring core in a single step is achieved by our pK_a concept for proceeding with the unfavorable equilibrium reactions.     

Microscopic Elucidation of Solid‐Electrolyte Interphase (SEI) Film Formation via Atomistic Reaction Simulations: Importance of Functional Groups of Electrolyte and Intact Additive Molecules

Secondary batteries such as Li‐ion battery are expected to be utilized as not only ubiquitous electric power sources such as mobile phones but also large‐scale electricity storage devices. Therefore, it is urgent to develop the higher performance secondary batteries. Their lifetime and stability are found to be strongly dependent on the nature of passivation film called solid electrolyte interphase (SEI) film formed on the anode surface in the initial charge‐discharge cycle. However, since it is difficult to directly observe the film formation processes in experiment, its microscopic mechanism is still not found. On the other hand, although the theoretical methods are useful complement to the experiment, some new methodologies are necessary to understand the long‐term processes of SEI film, which is produced as a result of that a lot of chemical reactions proceed simultaneously. Under the circumstances, we have developed Red Moon method that can simulate such complex chemical reaction systems, and were able to analyze for the first time the SEI film formation processes on the anode surface at the atomistic level. Then, we clarified theoretically the microscopic mechanism of the additive effect which is essential to improve the Na‐ion battery performance so as to enhance the SEI film formation. This new microscopic insight must provide an important guiding principle for use in designing the most suitable electrolytes for developing high‐performance secondary batteries.