Copper-Catalyzed Regio- and Stereoselective Formal Hydro(borylmethylsilyl)ation of Internal Alkynes via Alkenyl-to-Alkyl 1,4-Copper Migration.

Catalytic reactions involving 1,n-metal migration from carbon to carbon enable a nonclassical way of constructing organic molecular skeletons, rapidly providing complex molecules from relatively simple precursors. By utilization of this attractive feature, a new and efficient synthesis of alkenylsilylmethylboronates has been developed by formal hydro(borylmethylsilyl)ation of unsymmetric internal alkynes with silylboronates under copper catalysis. The reaction proceeds regioselectively and involves an unprecedented alkenyl-to-alkyl 1,4-copper migration. The reaction mechanism has been investigated by a series of kinetic, NMR, and deuterium-labeling experiments.

Organic Matter in the Asteroid Ryugu: What We Know So Far.

The Hayabusa2 mission was tasked with returning samples from the C-complex asteroid Ryugu (1999 JU3), in order to shed light on the formation, evolution and composition of such asteroids. One of the main science objectives was to understand whether such bodies could have supplied the organic matter required for the origin of life on Earth. Here, a review of the studies concerning the organic matter within the Ryugu samples is presented. This review will inform the reader about the Hayabusa2 mission, the nature of the organic matter analyzed and the various interpretations concerning the analytical findings including those concerning the origin and evolution of organic matter from Ryugu. Finally, the review puts the findings and individual interpretations in the context of the current theories surrounding the formation and evolution of Ryugu. Overall, the summary provided here will help to inform those operating in a wide range of interdisciplinary fields, including planetary science, astrobiology, the origin of life and astronomy, about the most recent developments concerning the organic matter in the Ryugu return samples and their relevance to understanding our solar system and beyond. The review also outlines the issues that still remain to be solved and highlights potential areas for future work.

Chiral Phosphoric Acid-Palladium(II) Complex Catalyzed Asymmetric Desymmetrization of Biaryl Compounds by C(sp3)-H Activation.

Desymmetrization is an essential method for the synthesis of chiral compounds, particularly chiral biaryls. We have developed an enantioselective synthesis of axially chiral biaryls by desymmetrization using C(sp3)-H activation catalyzed by chiral palladium phosphate. Mechanistic studies show that C-H activation is the rate- and enantiomer-determining step. To the best of our knowledge, this is the first report of asymmetric desymmetrization of axially chiral compounds by C(sp3)-H activation.

Palladium-catalyzed addition of acylsilanes across alkynes via the activation of a C-Si bond.

Palladium-catalyzed addition of a C-Si bond in acylsilanes across the triple bonds in an alkyne bearing a carbonyl group at one terminal is reported. The reaction proceeds with excellent regioselectivity, in which a silyl group is incorporated into the carbon α to the carbonyl group, allowing for straightforward access to a variety of functionalized alkenylsilane derivatives. Catalytic synthesis of indanones by annulation between acylsilanes and alkynes with an identical catalytic system is also reported.

Insights into the formation and evolution of extraterrestrial amino acids from the asteroid Ryugu.

All life on Earth contains amino acids and carbonaceous chondrite meteorites have been suggested as their source at the origin of life on Earth. While many meteoritic amino acids are considered indigenous, deciphering the extent of terrestrial contamination remains an issue. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent the most uncontaminated primitive extraterrestrial material available. Here, the concentrations of amino acids from two particles from different touchdown sites (TD1 and TD2) are reported. The concentrations show that N,N-dimethylglycine (DMG) is the most abundant amino acid in the TD1 particle, but below detection limit in the other. The TD1 particle mineral components indicate it experienced more aqueous alteration. Furthermore, the relationships between the amino acids and the geochemistry suggest that DMG formed on the Ryugu progenitor body during aqueous alteration. The findings highlight the importance of aqueous chemistry for defining the ultimate concentrations of amino acids in primitive extraterrestrial samples.

A 1,3-boron shift reaction of homoallenylboronates to synthesise 2-boryl-1,3-dienes.

We describe a 1,3-boron shift-type reaction of homoallenylboronates at the center (sp) carbon in allenes to afford 2-boryl-1,3-dienes with a variety of substituents. Notably, this reaction occurs in situ with allenylboronates in the presence of carbamate and a small excess of sec-BuLi, and it is not necessary to isolate the unstable homoallenylboronates.

Metal-free reduction of CO2 to formate using a photochemical organohydride-catalyst recycling strategy.

Increasing levels of CO2 in the atmosphere is a problem that must be urgently resolved if the rise in current global temperatures is to be slowed. Chemically reducing CO2 into compounds that are useful as energy sources and carbon-based materials could be helpful in this regard. However, for the CO2 reduction reaction (CO2RR) to be operational on a global scale, the catalyst system must: use only renewable energy, be built from abundantly available elements and not require high-energy reactants. Although light is an attractive renewable energy source, most existing CO2RR methods use electricity and many of the catalysts used are based on rare heavy metals. Here we present a transition-metal-free catalyst system that uses an organohydride catalyst based on benzimidazoline for the CO2RR that can be regenerated using a carbazole photosensitizer and visible light. The system is capable of producing formate with a turnover number exceeding 8,000 and generates no other reduced products (such as H2 and CO).

Using the Oral Assessment Guide to Predict the Onset of Pneumonia in Residents of Long-Term Care and Welfare Facilities: A One-Year Prospective Cohort Study.

Appropriate oral health care, depending on oral assessments, reduces the onset of pneumonia. However, the relationship between risk evaluation using an oral assessment tool and pneumonia in residents of long-term care facilities has not been fully elucidated. In the present study, we aim to examine the relationship between the total scores of the Oral Assessment Guide (OAG) and the incidence of pneumonia after a one-year baseline study of residents in long-term care facilities. The settings for sampling include nine long-term care facilities in Hokkaido. At baseline, there were 267 study subjects. A total of 72 individuals dropped out and 11 individuals met the exclusion criteria. Therefore, the subject sample included 184 individuals. Among the subjects included in our analyses, eight individuals developed pneumonia (six males and two females). A multiple logistic regression analysis was performed with the risk factors for developing pneumonia. Evaluations were performed based on the odds ratio (OR) and 95% confidence interval (CI). We observed that the OR for pneumonia onset was 2.29 (CI: 1.27-4.14) after being adjusted for pneumonia risk factors. Therefore, it was suggested that the total scores of the OAG could be used to screen for the risk of pneumonia onset in residents of long-term care and welfare facilities.

On the origin and evolution of the asteroid Ryugu: A comprehensive geochemical perspective.

Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned from the C-type asteroid Ryugu by the Hayabusa2 mission. On average Ryugu particles consist of 50% phyllosilicate matrix, 41% porosity and 9% minor phases, including organic matter. The abundances of 70 elements from the particles are in close agreement with those of CI chondrites. Bulk Ryugu particles show higher δ18O, Δ17O, and ε54Cr values than CI chondrites. As such, Ryugu sampled the most primitive and least-thermally processed protosolar nebula reservoirs. Such a finding is consistent with multi-scale H-C-N isotopic compositions that are compatible with an origin for Ryugu organic matter within both the protosolar nebula and the interstellar medium. The analytical data obtained here, suggests that complex soluble organic matter formed during aqueous alteration on the Ryugu progenitor planetesimal (several 10's of km), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation.

Catalytic Enantioselective Construction of Decalin Derivatives by Dynamic Kinetic Desymmetrization of C2-Symmetric Derivatives through Aldol-Aldol Annulation.

We have developed and investigated a catalytic desymmetrization reaction strategy that affords functionalized decalin derivatives with high enantioselectivities from C2-symmetric derivatives through aldol-aldol annulation. We identified the structural moieties of the catalyst necessary for the formation of the decalin derivative with high enantioselectivity. We elucidated the mechanisms of the catalyzed reactions: the first aldol reaction step was reversible, and the second aldol step was rate-limiting and stereochemistry-determining and was enantioselective. Using theoretical calculations guided by the experimental results, we identified the interactions between the catalyst and the transition state that led to the major enantiomer. The information obtained in this study will be useful for the development of catalysts and chemical transformations.

Intermolecular Catalytic Asymmetric Iodoetherification of Unfunctionalized Alkenes.

A newly prepared trinuclear Zn3-(R,S,S)-aminoiminobinaphthoxide complex (triZn-II) catalyzed the first general intermolecular asymmetric iodoetherification of unfunctionalized alkenes. Using triZn-II, the iodoetherification reaction of unfunctionalized alkenes with o-nitrophenols proceeded smoothly to give the products with up to 92.5:7.5 er, and diene substrates were converted to the products with up to 99:1 er with the formation of a meso-isomer (dl/meso = 78/22). The chiral iodoethers gave a new platform for the synthesis of chiral morpholines.

Palladium-Catalyzed Silylacylation of Allenes Using Acylsilanes.

We have developed a palladium-catalyzed addition of a C-Si bond of acylsilanes across a range of unactivated allenes. The reaction proceeds with complete regioselectivity, in which a silyl group binds to the central carbon of the allene, allowing for the straightforward access to functionalized alkenylsilane derivatives.

Palladium-Catalyzed Siloxycyclopropanation of Alkenes Using Acylsilanes.

Currently, catalytically transferable carbenes are limited to electron-deficient and neutral derivatives, and electron-rich carbenes bearing an alkoxy group (i.e., Fischer-type carbenes) cannot be used in catalytic cyclopropanation because of the lack of appropriate carbene precursors. We report herein that acylsilanes can serve as a source of electron-rich carbenes under palladium catalysis, enabling cyclopropanation of a range of alkenes. This reactivity profile is in sharp contrast to that of metal-free siloxycarbenes, which are unreactive toward normal alkenes. The resulting siloxycyclopropanes serve as valuable homoenolate equivalents, allowing rapid access to elaborate ß-functionalized ketones.

Applicability of composite materials for space radiation shielding of spacecraft.

Energetic ion beam experiments with major space radiation elements, 1H, 4He, 16O, 28Si and 56Fe, have been conducted to investigate the radiation shielding properties of composite materials. These materials are expected to be used for parts and fixtures of space vehicles due to both their mechanical strength and their space radiation shielding capabilities. Low Z materials containing hydrogen are effective for shielding protons and heavy ions due to their high stopping power and large fragmentation cross section per unit mass. The stopping power of the composite materials used in this work is intermediate between that of aluminum and polyethylene, which are typical structural and shielding materials used in space. The total charge-changing cross sections per unit mass, σUM, of the composite materials are 1.3-1.8 times larger than that of aluminum. By replacing conventional aluminum used for spacecraft with commercially available composite (carbon fiber / polyether ether ketone), it is expected that the shielding effect is increased by ∼17%. The utilization of composite materials will help mitigate the space radiation hazard on future deep space missions.

Enantioselective Epoxidation of 2,3-Disubstituted Naphthoquinones by a Side Chain Truncated Guanidine-Urea Bifunctional Organocatalyst.

An organocatalytic enantioselective epoxidation of 2,3-disubstituted naphthoquinones with tert-butyl hydroperoxide as an oxidant was developed using a guanidine-urea bifunctional catalyst lacking C2 symmetry, which was designed based upon the insights obtained from the DFT calculation model for our previous C2 symmetric catalyst. The present organocatalytic reaction provides access to a variety of optically active naphthoquinone epoxides bearing aryl and methyl substituents at C2 and C3 in high yields with high enantioselectivities (up to 97:3 er).

Phosphine-Catalyzed Intermolecular Acylfluorination of Alkynes via a P(V) Intermediate.

We report the phosphine-catalyzed intermolecular carbofluorination of alkynes using acyl fluorides as fluorinating reagents. This reaction promises to be a useful method for the synthesis of highly substituted monofluoroalkene derivatives since acyl fluorides can be easily prepared from the corresponding carboxylic acid derivatives and the reaction proceeds under ambient conditions without the need for a transition-metal catalyst. Experimental and computational studies indicate that a five-coordinate fluorophosphorane is involved as the key intermediate in the fluorination step.

Arylation of aryllithiums with S-arylphenothiazinium ions for biaryl synthesis.

Aryllithiums are one of the most common and important aryl nucleophiles; nevertheless, methods for arylation of aryllithums to produce biaryls have been limited. Herein, we report arylation of aryllithiums with S-arylphenothiazinium ions through selective ligand coupling of intermediary sulfuranes. Various unsymmetrical biaryls could be obtained without transition-metal catalysis.

Species diversity and phylogeography of Cornus kousa (Asian dogwood) captured by genomic and genic microsatellites.

Cornus kousa (Asian dogwood), an East Asia native tree, is the most economically important species of the dogwood genus, owing to its desirable horticultural traits and ability to hybridize with North America-native dogwoods. To assess the species genetic diversity and to better inform the ongoing and future breeding efforts, we assembled an herbarium and arboretum collection of 131 noncultivated C. kousa specimens. Genotyping and capillary electrophoresis analyses of our C. kousa collection with the newly developed genic and published nuclear genomic microsatellites permitted assessment of genetic diversity and evolutionary history of the species. Regardless of the microsatellite type used, the study yielded generally similar insights into the C. kousa diversity with subtle differences deriving from and underlining the marker used. The accrued evidence pointed to the species distinct genetic pools related to the plant country of origin. This can be helpful in the development of the commercial cultivars for this important ornamental crop with increased pyramided utility traits. Analyses of the C. kousa evolutionary history using the accrued genotyping datasets pointed to an unsampled ancestor population, possibly now extinct, as per the phylogeography of the region. To our knowledge, there are few studies utilizing the same gDNA collection to compare performance of genomic and genic microsatellites. This is the first detailed report on C. kousa species diversity and evolutionary history inference.

Investigation of shielding material properties for effective space radiation protection.

Geant4 Monte Carlo simulations were carried out to investigate the possible shielding materials of aluminum, polyethylene, hydrides, complex hydrides and composite materials for radiation protection in spacecraft by considering two physical parameters, stopping power and fragmentation cross section. The dose reduction with shielding materials was investigated for Fe ions with energies of 500 MeV/n, 1 GeV/n and 2 GeV/n which are around the peak of the GCR energy spectrum. Fe ions easily stop in materials such as polyethylene and hydrides as opposed to materials such as aluminum and complex hydrides including high Z metals with contain little or no hydrogen. Attenuation of the primary particles in the shielding and fragmentation into more lightly charged and therefore more penetrating secondary particles are competing factors: attenuation acts to reduce the dose behind shielding while fragmentation increases it. Among hydrogenous materials, 6Li10BH4 was one of the more effective shielding materials as a function of mass providing a 20% greater dose reduction compared to polyethylene. Composite materials such as carbon fiber reinforced plastic and SiC composite plastic offer 1.9 times the dose reduction compared to aluminum as well as high mechanical strength. Composite materials have been found to be promising for spacecraft shielding, where both mass and volume are constrained.

Iridium-Catalyzed ortho-C-H Borylation of Thioanisole Derivatives Using Bipyridine-Type Ligand.

A simple iridium catalytic system was developed that allows for a variety of 2-borylthioanisoles to be easily synthesized via ortho-selective C-H borylation of thioanisole derivatives. Once introduced, boryl and methylthio groups were converted by palladium-catalyzed transformations. Density functional theory calculations revealed that weak interactions, such as hydrogen bonding between the C-H bond of the SCH3 group and the oxygen atom of the boryl ligand, control the ortho-selectivity.