A Catalytic Alkylation of Ketones via sp3 C-H Bond Activation.

We identified a ternary hybrid catalyst system composed of an acridinium photoredox catalyst, a thiophosphoric imide (TPI) catalyst, and a titanium complex catalyst that promoted an intermolecular addition reaction of organic molecules with various ketones through sp3 C-H bond activation. The thiyl radical generated via single-electron oxidation of TPI by the excited photoredox catalyst abstracted a hydrogen atom from organic molecules such as toluene, benzyl alcohol, alkenes, aldehydes, and THF. The thus-generated carbon-centered radical species underwent addition to ketones and aldehydes. This intrinsically unfavorable step was promoted by single-electron reduction of the intermediate alkoxy radical by catalytically generated titanium(III) species. This reaction provided an efficient and straightforward route to a broad range of tertiary alcohols and was successfully applied to late-stage functionalization of drugs or their derivatives. The proposed mechanism was supported by both experimental and theoretical studies.

Chromium-Catalyzed Linear-Selective Alkylation of Aldehydes with Alkenes.

We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz's reagent. Photochemical homolysis of the C-Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction proceeded with high functional group tolerance at ambient temperature under visible-light irradiation.

Amine-tethered phenylboronic acid-enabling ring-opening strategy for carbon chain elongation from double aldol cyclic hemiacetals.

The addition of carbon nucleophiles to cyclic hemiacetal forms of double aldols is a promising approach toward the synthesis of structurally attractive 1,3-polyol derivatives. Cyclic hemiacetals are generally unreactive to carbon nucleophiles under neutral conditions, however, because the electrophilic aldehyde function is masked. Here we developed an amine-tethered phenylboronic acid 7g, which transforms double aldol cyclic hemiacetals to ring-opened linear aldehydes. Combined with the previously-developed copper-catalysed asymmetric double aldol reaction (L. Lin, K. Yamamoto, H. Mitsunuma, Y. Kanzaki, S. Matsunaga and M. Kanai, J. Am. Chem. Soc., 2015, 137, 15418), this method produced synthetically useful chiral building blocks containing a 1,3-di- or tri-ol moiety.

Frequency Extension to the THz Range in the High Pressure ESR System and Its Application to the Shastry-Sutherland Model Compound SrCu2(BO3)2.

We have made a survey of ceramics for the inner parts of the transmission-type pressure cell to achieve the high pressure and the high transmission in the THz range. By using the optimal combination of ZrO2-based ceramic and Al2O3 ceramic, we have succeeded in obtaining a pressure up to 1.5 GPa and a frequency region up to 700 GHz simultaneously. We show the high-pressure ESR results of the Shastry-Sutherland compound SrCu2(BO3)2 as an application. We observed the direct ESR transition modes between the singlet ground state and the triplet excited states up to a pressure of 1.51 GPa successfully, and obtained the precise pressure dependence of the gap energy. The gap energy is directly proved to be suppressed by the pressure. Moreover, we found that the system approaches the quantum critical point with pressure by comparing the obtained data with the theory. This result also shows the usefulness of high-pressure ESR measurement in the THz region to study quantum spin systems.

Surface Architecture of Sperm Tail Entry into the Hamster Oocyte.

At various times after artificial insemination in vivo, fertilized eggs were flushed from the ampulla of the oviduct of the hamster. The processes of sperm tail entry into the oocyte were studied with phase-contrast and electron microscopes. At 6-7 hr after insemination, the sperm head was incorporated completely into the ooplasm, but the entire length of the sperm tail still projected freely over the oocyte surface. The region on the oocyte surface where the second polar body was extruded was different from where the first polar body emerged. At 8-9 hr after insemination, the sperm tail was attached in a wave-like fashion to the oocyte surface. Where some portions of the tail were attached, they were trapped by the microvilli of the oocyte and had begun to sink into the ooplasm. Thus, the entire length of the sperm tail was incorporated into the ooplasm successively but almost synchronously. From the present observations, we have proposed a model for the mechanism of sperm tail entry into the vitellus in vivo.