Synthesis of Triarylpyridines in Thiopeptide Antibiotics by Using a C−H Arylation/Ring‐Transformation Strategy

We have described a C?H arylation/ring‐transformation strategy for the synthesis of triarylpyridines, which form the core structure of thiopeptide antibiotics. This synthetic method readily gave 2,3,6‐triarylpyridines in a regioselective manner by a two‐phase approach: C?H arylation (a nickel‐catalyzed decarbonylative Suzuki–Miyaura cross‐coupling and decarbonylative C?H coupling for the synthesis of 2,4‐diaryloxazoles) and ring transformation ([4+2] cycloaddition of 2,4‐diaryloxazoles with (hetero)arylacrylic acids). To showcase these methods, we have accomplished the formal synthesis of thiopeptide antibiotics GE2270 s and amythiamicins.     

Organocatalyst-mediated enantioselective intramolecular aldol reaction featuring the rare combination of aldehyde as nucleophile and ketone as electrophile

The trifluoroacetic acid salt of 2-(pyrrolidinylmethyl)pyrrolidine was found to be an effective organocatalyst of an asymmetric intramolecular aldol reaction, affording bicyclo[4.3.0]nonane derivatives with a high enantioselectivity, in which the rare combination of aldehyde as a nucleophile and ketone as an electrophile was realized.     

Production of iodine radionuclides using 7Li ion beams

Journal of Radioanalytical and Nuclear Chemistry - This is the first attempt to generate baseline data on the level of Naturally Occurring Radioactive Materials, (NORMs) 238U, 232Th and...     

Unique origin of colors of armchair carbon nanotubes

The colors of suspended metallic colloidal particles are determined by their size-dependent plasma resonance, while those of semiconducting colloidal particles are determined by their size-dependent band gap. Here, we present a novel case for armchair carbon nanotubes, suspended in aqueous medium, for which the color depends on their size-dependent excitonic resonance, even though the individual particles are metallic. We observe distinct colors of a series of armchair-enriched nanotube suspensions, highlighting the unique coloration mechanism of these one-dimensional metals.     

Decarbonylative C-h coupling of azoles and aryl esters: unprecedented nickel catalysis and application to the synthesis of muscoride a

A nickel-catalyzed decarbonylative C-H biaryl coupling of azoles and aryl esters is described. The newly developed catalytic system does not require the use of expensive metal catalysts or silver- or copper-based stoichiometric oxidants. We have successfully applied this new C-H arylation reaction to a convergent formal synthesis of muscoride A.     

Defect structure analysis of B-site doped perovskite-type proton conducting oxide BaCeO3 Part 1: The defect concentration of BaCe0.9M0.1O3−δ (M = Y and Yb)

By means of a high-temperature gravimetry, the defect chemical relationships between oxygen nonstoichiometry and water content in BaCe_0.9M_0.1O_3?δ (M = Y and Yb) were investigated as functions of partial pressure of oxygen, P(O₂), partial pressure of water vapor, P(H₂O), and temperature. Concentrations of protonic defect and that of oxygen vacancy strongly depend on P(H₂O) and temperature, while the dependences on P(O₂) were weak. The equilibrium constants of the water vapor incorporation reaction H₂O + V_O^??? + O_O^× = 2OH_O^? were determined. Concentrations of hole, [h^?], in the dry-atmospheres were determined by the weight gain by the incorporation of oxygen from the gas atmospheres. The [h^?] values increased with decreasing temperature. The [h^?] values were estimated to be about 2 to 3 orders of magnitude less than [OH_O^?] values measured in the wet-atmospheres.     

Effect of Y2O3 addition on the conductivity and elastic modulus of (CeO2)1 − x(YO1.5)x

The conductivity and elastic modulus of (CeO₂)_1 − x(YO_1.5)_x for x values of 0.10, 0.15, 0.20, 0.30, and 0.40 were investigated by experiments and molecular dynamics simulations. The calculated conductivity exhibited a maximum value at approximately 15 mol% Y₂O₃; this trend agreed with that of the experimental results. In order to clarify the reason for the occurrence of the maximum conductivity, the paths for the transfer of oxygen vacancies were counted. The numerical result revealed that as the content of Y₂O₃ dopant increases, the number of paths for the transfer of oxygen vacancies decreases, whereas the number of oxygen vacancies for conductivity increases. Thus, the trade-off between the increase in the number of vacancy sites and the decrease in the vacancy transfer was considered to be the reason for the maximum conductivity occurring at the Y₂O₃ dopant content of approximately 15 mol%. The calculated elastic modulus also exhibited a minimum value at approximately 20 mol% Y₂O₃, which also agreed with the experimental results. It was shown that the Y–O–Y bonding energy increased with the increasing content of Y₂O₃ dopant. Thus, the trade-off between the increase in the number of vacancy sites and that in the Y–O–Y bonding energy was considered to be the reason for the minimum elastic modulus occurring at the Y₂O₃ dopant content of approximately 20 mol%.     

One-pot preparation of Julia-Kocienski sulfides and sulfones from alcohols

A method for one-pot preparation of Julia-Kocienski sulfides and sulfones from alcohols and thiols is reported. A variety of primary alcohols were converted to the corresponding mesylates by methansulfonyl chloride and triethylamine in THF. After the reaction is complete, thiol (1 or 10) and either NaH or t-BuOK were added. The Julia-Kocienski sulfides 3, 9 and 11 were prepared by one-pot two steps procedure from alcohols in 76–96% yields (16 examples). Furthermore, after the sulfide formation, the reaction mixture was neutralized by p-toluenesulfonic acid and treated with H₂O₂ and ammonium molybdate in EtOH to give the Julia-Kocienski sulfones 4 in good yields except for trans-2-hexen-1-ol.     

Ring-opening fluorination of bicyclic azaarenes

We have discovered a ring-opening fluorination of bicyclic azaarenes. Upon treatment of bicyclic azaarenes such as pyrazolo[1,5-a]pyridines with electrophilic fluorinating agents, fluorination of the aromatic ring is followed by a ring-opening reaction. Although this overall transformation can be classified as an electrophilic fluorination of an aromatic ring, it is a novel type of fluorination that results in construction of tertiary carbon–fluorine bonds. The present protocol can be applied to a range of bicyclic azaarenes, tolerating azines and a variety of functional groups. Additionally, mechanistic studies and enantioselective fluorination have been examined.

A ring-opening fluorination of bicyclic azaarenes was developed. Although this overall transformation can be classified as an electrophilic fluorination of aromatics, it is a novel type of fluorination that results in construction of tert-C–F bonds.