Synthesis of 2-hydroxytetrahydrofurans by Wacker-type oxidation of 1,1-disubstituted alkenes.

1,1-Disubstituted alkenes feature high steric hindrance, which renders their Wacker-type oxidation difficult. We demonstrate the stereoselective synthesis of 2-hydroxytetrahydrofurans via the Wacker-type oxidation of 3-methyl-3-buten-1-ols by using a PdCl2(MeCN)2/NO/BQ catalyst system under 1 atm O2 in H2O or H2O/DMF.

High-precision flat-plate reference infrared radiator using perfect blackbody composite with a microcavity structure.

Onsite reference infrared radiators are used to correct thermal imagers for noncontact fever screening in real time. We have developed a flat-plate reference radiator of the highest accuracy to enhance reliability of the fever screening. Our contact-durable blackbody composite with good heat transfer, which has a microcavity structured surface offering high emissivity (>0.999), was employed for the emissive surface of the reference radiator. Evaluation of the developed reference radiator regarding the spectral emissivity, in-plane uniformity, and temperature stability demonstrated an unprecedentedly small uncertainty of 0.10°C for the radiance temperature (95% level of confidence).

Micro-cavity perfect blackbody composite with good heat transfer towards a flat-plate reference radiation source for thermal imagers.

One of the key measures to secure reliable fever screening is to calibrate a thermal imager with an accurate flat-plate blackbody device in real time. We provide durable perfect blackbody plates with both high emissivity of >0.998 and good heat transfer, ideal for a high-precision reference radiation source. Reflectance measurements and heat transfer simulation demonstrate that a micro-cavity composite of a thin resin double layer or resin mixture with thermally conductive filler is an important solution for improving the emissivity and thermal performance of blackbody plates.

Large-area perfect blackbody sheets having aperiodic array of surface micro-cavities for high-precision thermal imager calibration.

We present a large-area perfect blackbody sheet, which would offer a planar standard radiator for high-precision thermal imager calibration. Polydimethylsiloxane (PDMS) sheets with nano-precision surface micro-cavity structures achieve both ultra-low reflectance (ultra-high emissivity close to unity) over the thermal infrared wavelengths and high durability to mechanical contact. The investigation on the geometrical parameters of the conical micro-cavities, that is, radii and aspect ratios (ratio of height to radius), confirmed that the PDMS blackbody sheet with a micro-cavity radius of ∼6 µm and an aspect ratio of ∼4 exhibits the optimum hemispherical reflectance of less than 0.002 (emissivity of higher than 0.998) at the thermal infrared wavelengths (6-15 µm). Furthermore, the large-area PDMS blackbody sheet of 100 mm × 80 mm maintained an excellent in-plane uniformity of the emissivity. This unprecedented large-area perfect blackbody conforms to the International Electrotechnical Commission (IEC) standard recommendation regarding thermal imager calibration for fever screening in terms of the emissivity performance.

Construction of a CF3-Containing Benzofurofuranone Skeleton from Coumarins via Reductive Coupling and Acid-Mediated Ring Contraction.

Magnesium-promoted reductive introduction of a trifluoroacetyl group to coumarin in the presence of ethyl trifluoroacetate and the subsequent treatment with trifluoroacetic acid led to simple access to a trifluoromethylated benzofurofuranone at 8a-position with a high regio- and stereoselectivity. Trifluoromethylated or difluoromethylated benzofurofuranone derivatives were also prepared from coumarins including naturally occurring ones only in two successive steps, which might have potential bioactivity in medicinal chemistry.

Site-Selective Doping and Site-Sensitive Photoluminescence of Eu3+ and Tb3+ in Perovskite-Type LaLuO3.

Eu3+ and Tb3+ ions were site-selectively doped into LaLuO3 with the orthorhombic perovskite-type structure (ABO3), and their luminescence properties were examined considering the doping sites (A or B sites). The X-ray diffraction analysis revealed the expansion or contraction of the unit cell volumes of the materials depending on the doping sites. The spectra of X-ray absorption near edge structure for the Eu and Tb LIII edge exhibited different shapes for the ions at A and B sites, confirming the site-selective doping of Eu3+ and Tb3+ in LaLuO3. The photoluminescence (PL) and PL excitation (PLE) spectra of the materials also showed some differences caused by the doping sites. The intensities of the Eu3+ PL peaks derived from the 5D0-7F1 transitions and those from the 5D0-7F2 transitions were markedly different between Eu3+ at A sites and those at B sites because of the different site symmetries. The splitting of the intense Tb3+ PL peaks originating from the 5D4-7F5 transitions and the absence of PL peaks from 5D3-7FJ transitions were found only for Tb3+ at B sites because of the strong crystal field at B sites. In addition to the PL spectra, the positions of PLE peaks originating from charge transfer transitions in Eu3+ and the 4f-5d transitions in Tb3+ depended on the doping sites. The successful site-selective doping enabled us to clarify the site-sensitive luminescence properties of Eu3+ and Tb3+ doped in the perovskite-type LaLuO3.

Luminescence and Location of Gd3+ or Tb3+ Ions in Perovskite-Type LaScO3.

The luminescence properties of Gd3+ or Tb3+ ions at La and Sc sites were investigated in LaScO3 with a distorted perovskite-type structure (ABO3). Although the luminescence of lanthanide ions located at B sites is not common and has not been examined in detail, Gd3+ or Tb3+ luminescence from B sites and A sites is clearly observed in Gd3+- or Tb3+-doped LaScO3. The differences in the luminescence characteristics concern peak positions, peak shapes, and decay time, which are all influenced by the crystal field and the site symmetry. The UV luminescence of Gd3+ at B sites shows a red shift compared to Gd3+ at A sites, and the green luminescence of Tb3+ at B sites contrasts with the blue-violet and green luminescence of Tb3+ at A sites. The decay time of the luminescence from B sites is systematically longer than that from A sites in both the Gd3+ and Tb3+ cases.

Luminescence and Valence of Tb Ions in Alkaline Earth Stannates and Zirconates Examined by X-ray Absorption Fine Structures.

The difference in Tb3+ green luminescence intensities in doped perovskite(ABO3)-type alkaline earth stannates, AeSnO3 (Ae = Ca, Sr, Ba), and the Mg codoping effect on the luminescence intensities in doped CaMO3 (M = Sn, Zr) were investigated utilizing the X-ray absorption fine structures (XAFS) of the Tb LIII absorption edge. It is considered that the local symmetry at A sites is responsible for the different Tb3+ luminescence intensities in AeSnO3 (Ae = Ca, Sr, Ba) doped with Tb ions at A sites. However, it was found from the XAFS spectra that some Tb ions are unintentionally stabilized at B sites as Tb4+, especially in BaSnO3. Not only the central symmetry for Tb3+ at A sites but also the presence of Tb4+ at B sites were considered to bring about the absence of Tb3+ luminescence in doped cubic BaSnO3. No obvious changes in the Tb3+ local structure at A sites were detected between Tb single doped and Tb-Mg codoped CaMO3 (M = Sn, Zr) from the extended XAFS oscillation, but the trace of Tb4+ at B sites in the Tb single doped sample was observed in the X-ray absorption near edge structures. It is, therefore, considered that the Tb3+ luminescence enhancement by Mg codoping is primarily attributed to the charge compensation rather than the changes in the local structure around Tb3+ at A sites.

Supreme-black levels enabled by touchproof microcavity surface texture on anti-backscatter matrix.

Emerging immersive high-dynamic range display technologies require not only high peak luminance but also true black levels with hemispherical reflectance below 0.001 (0.1%) to accommodate the wide dynamic range of the human eye (~105). Such low reflectance materials, denoted here as "supreme black," must exhibit near-perfect surface antireflection, extremely low in-matrix backscattering, and sufficient optical thickness, which, to date, have only been achieved by fragile sparse materials. We demonstrate a record-low hemispherical reflectance below 0.0002 (absorptance above 0.9998) in a touchproof material by satisfying the three requirements with a superwavelength surface microtexture with nanolevel details, low Mie backscattering composition, and optional additional underlayer. Our supreme black finishes are one to two orders of magnitude blacker than previously developed touchproof super-black materials. Thereby, unprecedented black levels enabling an ambient contrast ratio of ≳104 would be provided in display devices, contributing to immersive visual experiences that are critical for seamless remote collaboration and reliable virtual health care.

Microwave-assisted deacylation of unactivated amides using ammonium-salt-accelerated transamidation.

The combination of an ammonium salt and ethylenediamine promotes deacylation of a variety of unactivated amides to give the corresponding amines in high yields without the use of strong acids or bases. The reactions proceed without special care regarding air and moisture, and tolerate a wide range of functional groups.

Growth and superconductivity of niobium titanium alloy thin films on strontium titanate (001) single-crystal substrates for superconducting joints.

Aiming to introduce NbTi alloy superconducting joints for REBa2Cu3O7-δ (REBCO, RE: rare-earth element) superconducting wires, NbTi alloy thin films were deposited at room temperature on SrTiO3 (STO) (001) single-crystal substrates, which have a high lattice matching with REBCO (001). The strain, crystallinity, surface morphology, and superconducting property of the films with various thicknesses were investigated. The NbTi films grew in the orientation with (110)NbTi//(001)STO:[001]NbTi and [11-0] NbTi//[100]STO; that is, the NbTi lattices had two directions in the (110) of NbTi. The strain decreased and the crystallinity improved as the film thickness increased. The films were found to crystallize immediately at the interface between the films and substrates by cross-sectional scanning transmission electron microscopy. The flat surfaces of the films have mesh-like morphologies due to the growth of elongated NbTi grains along the [100] and [010] of the STO, reflecting the in-plane two directions of the NbTi lattices. The superconducting transition temperature of the films increased with improvement in the crystallinity of the films. The preparation of superconducting NbTi alloy thin films with sufficient crystallinity at room temperature suggested the possibility of forming the films on REBCO and the applicability of the films as superconducting joints.

Diethylenetriamine-Mediated Direct Cleavage of Unactivated Carbamates and Ureas.

Diethylenetriamine is effective for the direct cleavage of unactivated carbamates and ureas without additional reagents and catalysts. Various carbamates and ureas were cleaved to afford products in good yield, and the reactions were not affected by air or moisture. Unique chemoselective cleavage of carbamate and urea in the presence of amides was also achieved.

Lanthanum(III) triflate catalyzed direct amidation of esters.

Lanthanum trifluoromethanesulfonate is an effective single-component catalyst for synthesizing a variety of amides directly from esters and amines under mild conditions. Highly selective amidation of esters and amines, as well as catalyst-controlled amidation of esters, demonstrated the effectiveness of the catalyst system.

Cleavage of unactivated amide bonds by ammonium salt-accelerated hydrazinolysis.

Hydrazinolysis of unactivated amide bonds is significantly accelerated by the addition of ammonium salts. The reactions proceed at 50-70 °C to give amines with broad substrate scope that outperforms existing amide bond cleavage reactions. Application to peptide and amino sugar derivatives is also demonstrated.