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271 results on '"Murafuji, Toshihiro"'

3. Photoinduced Aryl Ketone-Catalyzed Phenylation of C(sp3)–H Bonds Attached to the Heteroatom of Ethers and N -Boc-Amines via Concerted Homolytic Aromatic Substitution.

Author

Azami, Masaya, Sumimoto, Michinori, Nakamura, Reika, Murafuji, Toshihiro, and Kamijo, Shin

Subjects
ABSTRACTION reactions, KETONES, RADICALS (Chemistry), PHOTOCHEMISTRY, ETHERS, BENZENE derivatives
Abstract

A single-step phenylation at the non-acidic C(sp3)–H bond attached to the heteroatom of ethers and N -Boc-amines has been achieved using photoexcited 4-benzoylpyridine as a hydrogen atom transfer (HAT) catalyst. The design of electron-deficient (trifluoromethylsulfonyl)benzene derivatives, as a phenyl precursor, was critical to realizing the present transformation. Moreover, the DFT calculations indicated that the present transformation proceeds via a concerted homolytic aromatic substitution rather than via a stepwise one involving the formation of a cyclohexadienyl radical intermediate. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Efficient Synthesis and Structural Analysis of Chiral 4,4′‐Biazulene

Author

Hatakenaka, Ryoji, primary, Nishikawa, Nanami, additional, Mikata, Yuji, additional, Aoyama, Hiroki, additional, Yamashita, Kohsuke, additional, Shiota, Yoshihito, additional, Yoshizawa, Kazunari, additional, Kawasaki, Yuuya, additional, Tomooka, Katsuhiko, additional, Kamijo, Shin, additional, Tani, Fumito, additional, and Murafuji, Toshihiro, additional

Published
2024
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5. Color Change of Indole Squaraine between Blue and Yellow with Golden Luster

Author

Yamazaki, Suzuko, Okazaki, Taisei, Murafuji, Toshihiro, Sumimoto, Michinori, and Mikata, Yuji

Abstract

Color change of materials by external stimulus has attracted much attention for various applications. We synthesized 1,3-bis(3,3-dimethyl-2-methylene indolenine)squaraine (ISQ), which was a yellow powder with golden luster (ISQ(gold)) and whose color changed to blue (ISQ(blue)) by being ground using mortar and pestle. Scanning electron microscopy indicated that ISQ(gold) consisted of laminated plate-like crystals with a large flat surface, which was attributable to (2 0–2) facets of monoclinic crystals. Measurements of the diffuse reflectance spectra revealed that J- and H-type aggregates of ISQ were formed by increasing the weight percent of ISQ(blue) in the mixture with BaSO4. A thin film, which was prepared by a spin-coating of ethanol with dissolved ISQ(blue) on glass substrates, looked blue on a white paper, whereas it looked yellowish on a black paper. By repeating the coating process, the film thickness increased, and the thick film exhibited yellow with golden luster regardless of the background color. These results indicate that the color depends on whether the transmitted light through ISQ or the reflected light on the ISQ surface mainly contributes to color vision. To neglect the effect of the transmitted light and intensify the reflection on the surface, a pellet with a smooth surface was prepared by pressing ISQ(gold) or ISQ(blue) at 20 kg/cm2. The ISQ(blue) pellet consisted of the laminated sheets and was dark blue-green. However, under light irradiation, the ISQ(blue) pellet exhibited a yellow color with golden luster, whose specular reflection spectrum was similar to that of the ISQ(gold) pellet. Our results indicate that the color of ISQ is tunable by controlling the transmission and the reflection of the light, including the specular and diffuse reflections.

Published
2024
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7. Aryl Ketone‐Catalyzed Light‐Driven Radical Oxy‐Functionalization of Non‐Acidic C(sp3)−H Bonds Enabled by Triple Role of TEMPO.

Author

Kamijo, Shin, Azami, Masaya, Kamijo, Kaori, Umeno, Hina, Ishii, Ryo, and Murafuji, Toshihiro

Subjects
RADICALS (Chemistry), KETONES, HOMOLYSIS, ALCOHOL oxidation
Abstract

A light‐driven radical oxy‐functionalization of non‐acidic aliphatic and benzylic C(sp3)−H bonds was achieved with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) in a single‐step by employing an aryl ketone as a sole catalyst. The transformation was initiated by homolysis of a C(sp3)−H bond in the starting substance by the photo‐excited aryl ketone. The derived carbon radical was then promptly trapped by TEMPO leading to the formation of the TEMPO‐adduct. The derived TEMPO‐adduct is synthetically versatile as an alcohol equivalent since it can be readily converted to the corresponding ketone by oxidation and to the corresponding alcohol by reduction. The key to realizing the present catalytic reaction relies on the distinctive triple role of TEMPO, which acts as the precursor of the oxygen functionality, the oxidant to regenerate the aryl ketone, and the protective group for the derived TEMPO‐adduct from over‐oxidation. [ABSTRACT FROM AUTHOR]

Published
2024
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14. Aryl Ketone Mediated Light-Driven Naphthylation of C(sp3)–H Bonds Attached to either Oxygen or Nitrogen Substituents.

Author

Azami, Masaya, Murafuji, Toshihiro, and Kamijo, Shin

Subjects
*KETONES, *NITROGEN, *OXYGEN, *INTERSTITIAL hydrogen generation, *NAPHTHALENE, *CHEMOSELECTIVITY, *CARBON, *SCISSION (Chemistry)
Abstract

A light-driven naphthylation was achieved at C(sp3)–H bonds attached to either oxygen or nitrogen substituents using sulfonylnaphthalenes as a naphthalene precursor in the presence of 4-benzoylpyridine at ambient temperature. The present transformation is proposed to proceed through the generation of a carbon radical species via chemoselective cleavage of the heteroatom-substituted C(sp3)–H bond by photoexcited 4-benzoylpyridine, the addition of the derived carbon radical to the electron-deficient sulfonylnaphthalene, and then rearomatization by releasing sulfinyl radical. [ABSTRACT FROM AUTHOR]

Published
2022
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17. Structure and properties of 3-(diethylboryl)pyridines

Author

Sugihara, Yoshikazu, Takakura, Katsuto, Murafuji, Toshihiro, Miyatake, Ryuta, Nakasuji, Kazuhiro, Kato, Masako, and Yano, Shigenobu

Subjects
Boron -- Research, Cyclic compounds -- Research, Biological sciences, Chemistry
Abstract

1H and 13C spectra of 3-(diethylboryl)pyridine showed that the boryl group does not act only as a pi-acceptor and that the boron atom is shielded by ca. 50 ppm even when compared with trivalent boron atoms conjugated with the pi-donor. A single-crystal X-ray crystallographic study indicated the formation of a cyclic-tetramer with a void via the intermolecular boron-nitrogen coordination bond. 3-(Diethylboryl)pyridines comprise the rigid cyclic-tetramer in solution at ambient temperature.

Published
1996

21. An Azulene-Based Chiral Helicene and Its Air-Stable Cation Radical

Author

Narita, Masahiro, primary, Teraoka, Takaaki, additional, Murafuji, Toshihiro, additional, Shiota, Yoshihito, additional, Yoshizawa, Kazunari, additional, Mori, Shigeki, additional, Uno, Hidemitsu, additional, Kanegawa, Shinji, additional, Sato, Osamu, additional, Goto, Kenta, additional, and Tani, Fumito, additional

Published
2019
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27. A new efficient route to 2-substituted azulenes based on sulfonyl group directed lithiation

Author

Shibasaki, Toshihisa, Ooishi, Takeo, Yamanouchi, Nobuhiko, Murafuji, Toshihiro, Kurotobi, Kei, and Sugihara, Yoshikazu

Subjects
Lithium compounds -- Chemical properties, Organosulfur compounds -- Chemical properties, Substitution reactions -- Analysis, Biological sciences, Chemistry
Abstract

The versatile application of the sulfonyl group to azulene systems is discussed. A convenient synthesis method of 2-substituted azulenes based on sulfonyl group directed lithiation is reported.

Published
2008

28. Two-photon absorption properties of azylenyl compounds having a conjugated ketone

Author

Hirakawa, Shoichiro, Kawamata, Jun, Suzuki, Yasutaka, Tani, Seiji, Murafuji, Toshihiro, Kasatani, Kazuo, Antonov, Liudmil, Kamada, Kenji, and Ohta, Koji

Subjects
Ketones -- Spectra, Photons -- Spectra, Chemicals, plastics and rubber industries
Abstract

Two-photon absorption (TPA) properties of conjugated ketone derivatives that include nonalternant azulenyl moieties in the [pi]-conjugation system are described. The results have shown that a compound having an azulenyl moiety can be used as a TPA material.

Published
2008

38. An Azulene‐Fused Tetracene Diimide with a Small HOMO–LUMO Gap

Author

Koide, Taro, primary, Takesue, Moritaka, additional, Murafuji, Toshihiro, additional, Satomi, Koichiro, additional, Suzuki, Yasutaka, additional, Kawamata, Jun, additional, Terai, Kengo, additional, Suzuki, Mitsuharu, additional, Yamada, Hiroko, additional, Shiota, Yoshihito, additional, Yoshizawa, Kazunari, additional, and Tani, Fumito, additional

Published
2016
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41. Synthesis and Structural Characterization of Diazulenylborinic Acid

Author

Ishiguro Katsuya, Shintaku Kohhei, Mikata Yuji, Murafuji Toshihiro, Kamijo Shin, and Nagao Kouhei

Subjects
Pharmacology, 010405 organic chemistry, Chemistry, Organic Chemistry, 010402 general chemistry, 01 natural sciences, Combinatorial chemistry, 0104 chemical sciences, Analytical Chemistry, Characterization (materials science)
Published
2017
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46. An Azulene-Fused Tetracene Diimide with a Small HOMO-LUMO Gap.

Author

Koide, Taro, Takesue, Moritaka, Murafuji, Toshihiro, Satomi, Koichiro, Suzuki, Yasutaka, Kawamata, Jun, Terai, Kengo, Suzuki, Mitsuharu, Yamada, Hiroko, Shiota, Yoshihito, Yoshizawa, Kazunari, and Tani, Fumito

Subjects
AZULENE, IMIDES, ABSORPTION spectra, TWO-photon absorbing materials, N-type semiconductors
Abstract

A newly prepared tetraazulene-fused tetracene diimide (TA-fused TDI) showed absorption in the near-IR region owing to the effective extension of the π-conjugated system as well as a large two-photon absorption cross-section ( σ(2)=2140 GM) at 950 nm. Four reversible reduction processes and n-type semiconductivity were also confirmed as attractive electronic properties of this compound. [ABSTRACT FROM AUTHOR]

Published
2017
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