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1. Catalytic Asymmetric Synthesis of 2,6‐Disubstituted Cuneanes via Enantioselective Constitutional Isomerization of 1,4‐Disubstituted Cubanes

Author

90190496, Takebe, Hiyori, Matsubara, Seijiro, 90190496, Takebe, Hiyori, and Matsubara, Seijiro

Abstract

2, 6-Disubstituted cuneane has potential as a p -disubstituted benzene bioisostere and a novel chiral scaffold. It is a constitutional isomer of a 1, 4-disubstituted cubane obtained via a metal-catalyzed skeletal rearrangement. Unlike the highly symmetrical 1, 4-disubstituted cubane, the isomerized 2, 6-disubstituted cuneane is a chiral molecule possessing C 2 symmetry. Examining various chiral catalysts revealed that the Pd-pincer catalyst provides a good asymmetric induction.

Published
2022

2. Non-enzymatic catalytic asymmetric cyanation of acylsilanes

Author

90190496, Nagano, Tagui, Matsumoto, Akira, Yoshizaki, Ryotaro, Asano, Keisuke, Matsubara, Seijiro, 90190496, Nagano, Tagui, Matsumoto, Akira, Yoshizaki, Ryotaro, Asano, Keisuke, and Matsubara, Seijiro

Abstract

The asymmetric cyanation of acylsilanes affords densely functionalized tetrasubstituted chiral carbon centers bearing silyl, cyano, and hydroxy groups, which are of particular interest in synthetic and medicinal chemistry. However, this method has been limited to a few enzymatic approaches, which employ only one substrate because of substrate specificity. Here we show the non-enzymatic catalytic asymmetric cyanation of acylsilanes using a chiral Lewis base as an enantioselective catalyst, trimethylsilyl cyanide as a cyanating reagent, and isopropyl alcohol as an additive to drive catalyst turnover. High enantio- and site-selectivities are achieved in a catalytic manner, and a variety of functional groups are installed in optically active acylsilane cyanohydrins, thus overcoming the limitations imposed by substrate specificity in conventional enzymatic methods. A handle for the synthetic application of the products is also established through the development of a catalyst for protecting acylsilane cyanohydrins, which are unstable and difficult to protect alcohols.

Published
2022

3. Catalytic asymmetric cycloetherification via intramolecular oxy-Michael addition of enols

Author

90711771, 90190496, Murata, Ryuichi, Asano, Keisuke, Matsubara, Seijiro, 90711771, 90190496, Murata, Ryuichi, Asano, Keisuke, and Matsubara, Seijiro

Abstract

Carbonyl compounds employed as carbon nucleophiles have played a dominant role in synthetic organic chemistry; however, there is very limited use of these compounds as oxygen nucleophiles. In particular, there are only a few reports on the oxy-Michael addition of the enol forms of carbonyl nucleophiles. In this study, we present the asymmetric cycloetherification of enols, which are generated in situ from enone-bearing ketones, using chiral bifunctional organocatalysts bearing amino and squaramide groups. This transformation chemo-and enantioselectively afforded dihydropyran derivatives, which are the core structures of building blocks for synthesizing glycans.

Published
2021

4. Enantioselective bromination of axially chiral cyanoarenes in the presence of bifunctional organocatalysts

Author

90711771, 90190496, Wada, Yuuki, Matsumoto, Akira, Asano, Keisuke, Matsubara, Seijiro, 90711771, 90190496, Wada, Yuuki, Matsumoto, Akira, Asano, Keisuke, and Matsubara, Seijiro

Abstract

Enantioselective bromination of axially chiral cyanoarenes bearing high intrinsic rotational barriers via dynamic kinetic resolution using bifunctional organocatalysts is reported. Sequential addition of a brominating reagent in several portions at an optimized temperature was effective in accomplishing high enantioselectivities.

Published
2019

5. Organocatalytic enantio- and diastereoselective cycloetherification via dynamic kinetic resolution of chiral cyanohydrins

Author

90711771, 90190496, Yoneda, Naoki, Fujii, Yuki, Matsumoto, Akira, Asano, Keisuke, Matsubara, Seijiro, 90711771, 90190496, Yoneda, Naoki, Fujii, Yuki, Matsumoto, Akira, Asano, Keisuke, and Matsubara, Seijiro

Abstract

Enantioselective approaches to synthesize six-membered oxacycles with multiple stereogenic centres are in high demand to enable the discovery of new therapeutic agents. Here we present a concise organocatalytic cycloetherification for the highly enantio- and diastereoselective synthesis of tetrahydropyrans involving simultaneous construction of two chiral centres, one of which is fully substituted. This method involves dynamic kinetic resolution of reversibly generated chiral cyanohydrins. A chiral bifunctional organocatalyst selectively recognizes a specific chair-like conformation of the intermediate, in which the small steric effect of the linear cyano group as well as its anomeric effect play important roles in controlling stereoselectivity. The products offer additional utility as synthetic intermediates because the cyano group can be further transformed into a variety of important functional groups. This strategy provides a platform to design efficient approaches to obtain a wide range of optically active tetrahydropyrans, which are otherwise synthetically challenging materials.

Published
2017

6. A chiral phosphoric acid catalyst for asymmetric construction of 1,3-dioxanes.

Author

90711771, 90190496, Matsumoto, Akira, Asano, Keisuke, Matsubara, Seijiro, 90711771, 90190496, Matsumoto, Akira, Asano, Keisuke, and Matsubara, Seijiro

Abstract

A novel method of enantioselective 1, 3-dioxane construction via a hemiacetalization/intramolecular oxy-Michael addition cascade by a chiral phosphoric acid catalyst was developed. The product was successfully transformed into an optically active 1, 3-polyol motif, indicating that the proposed reaction can provide useful chiral building blocks for the de novo synthesis of polyketides.

Published
2015

9. Asymmetric Cycloetherifications by Bifunctional Aminothiourea Catalysts: The Importance of Hydrogen Bonding

Author

90711771, 90190496, Fukata, Yukihiro, Miyaji, Ryota, Okamura, Takaaki, Asano, Keisuke, Matsubara, Seijiro, 90711771, 90190496, Fukata, Yukihiro, Miyaji, Ryota, Okamura, Takaaki, Asano, Keisuke, and Matsubara, Seijiro

Abstract

Chiral oxacyclic frameworks are prevalent in many natural products and bioactive compounds. In addition, a number of them are important synthetic intermediates. Thus, the synthesis of such structures is a significant goal in the field of organic chemistry. However, the development of catalytic asymmetric cycloetherification for the straightforward synthesis of these compounds remains a challenge. In this study, we propose the use of aminothiourea catalysis as an effective way to accomplish such a challenge. The asymmetric synthesis of chiral oxygen heterocycles, including tetrahydrofurans, tetrahydropyrans, and 1, 3-dioxolanes, is demonstrated herein using intramolecular oxy-Michael addition mediated by bifunctional aminothiourea catalysts.

Published
2013

13. Reaction Pathway of Methylenation of Carbonyl Compounds with Bis(iodozincio)methane

Author

00111922, 90190496, Sada, Mutsumi, Komagawa, Shinsuke, Uchiyama, Masanobu, Kobata, Masami, Mizuno, Tsuyoshi, Utimoto, Kiitiro, Oshima, Koichiro, Matsubara, Seijiro, 00111922, 90190496, Sada, Mutsumi, Komagawa, Shinsuke, Uchiyama, Masanobu, Kobata, Masami, Mizuno, Tsuyoshi, Utimoto, Kiitiro, Oshima, Koichiro, and Matsubara, Seijiro

Published
2010

38. Formation of Cu nanoparticles by electroless deposition using aqueous CuO suspension

Author

90173864, 90190496, 40324826, Yagi, Shunsuke, Nakanishi, Hidetaka, Matsubara, Eiichiro, Matsubara, Seijiro, Ichitsubo, Tetsu, Hosoya, Kazuo, Matsuba, Yorishige, 90173864, 90190496, 40324826, Yagi, Shunsuke, Nakanishi, Hidetaka, Matsubara, Eiichiro, Matsubara, Seijiro, Ichitsubo, Tetsu, Hosoya, Kazuo, and Matsuba, Yorishige

Published
2008

41. Cesium fluorohydrogenate, Cs(FH)₂.₃F

Author

30574016, 30237911, 90190496, Matsumoto, Kazuhiko, Ohtsuki, Junya, Hagiwara, Rika, Matsubara, Seijiro, 30574016, 30237911, 90190496, Matsumoto, Kazuhiko, Ohtsuki, Junya, Hagiwara, Rika, and Matsubara, Seijiro

Abstract

Cs(FH)₂.₃F is a liquid salt exhibiting a low viscosity of 20.1 cP and a high conductivity of 86.3 mS cm⁻¹ at 25 °C, in spite of the relatively high melting point (16.9 °C). The high density of 2.82 g cmÄ⁻³ at the liquid state is due to the heavy atomic weight and small size of cesium atom compared to the organic cations of general ionic liquids. The infrared spectroscopy indicates that this salt contains (FH)₂F⁻ as a main anionic species. The other anionic species such as (FH)₃F⁻ found in the cases of other M⁺(HF)₂.₃F (M = a univalent organic cation) ionic liquid salts is not detected, suggesting its small abundance as well as the presence of neutral HF in the form of molecular and/or oligomers. The result of ¹H NMR also suggests that the anions exchange HF between them. These observations coincide with the experimental result that Cs(FH)₂.₃F acts as an acid against general ionic liquid fluorohydrogenates such as EMIm(FH)₂.₃F (EMIm = 1-ethyl-3-methylimidazolium) to lose HF and give Cs(FH)₂F precipitate.

Published
2006

42. Dynamic motion of building blocks in porous coordination polymers

Author

70552652, 00402959, 90190496, 20140303, Horike, S, Matsuda, R, Tanaka, D, Matsubara, S, Mizuno, M, Endo, K, Kitagawa, S, 70552652, 00402959, 90190496, 20140303, Horike, S, Matsuda, R, Tanaka, D, Matsubara, S, Mizuno, M, Endo, K, and Kitagawa, S

Published
2006

44. Fluorination with ionic liquid EMIMF(HF)2.3 as mild HF source

Author

30574016, 30237911, 20589189, 00111922, 90190496, Yoshino, H, Matsumoto, K, Hagiwara, R, Ito, Y, Oshima, K, Matsubara, S, 30574016, 30237911, 20589189, 00111922, 90190496, Yoshino, H, Matsumoto, K, Hagiwara, R, Ito, Y, Oshima, K, and Matsubara, S

Published
2006

49. Structure of bis(iodozincio)methane in THF solution

Author

90190496, 00111922, 40165783, 90173864, Matsubara, S, Oshima, K, Matsuoka, H, Matsumoto, K, Ishikawa, K, Matsubara, E, 90190496, 00111922, 40165783, 90173864, Matsubara, S, Oshima, K, Matsuoka, H, Matsumoto, K, Ishikawa, K, and Matsubara, E

Published
2005

50. Structure and reactivity of bis(iodozincio)methane solution

Author

90190496, 00111922, 40165783, 90173864, Matsubara, S, Yoshino, H, Yamamoto, Y, Oshima, K, Matsuoka, H, Matsumoto, K, Ishikawa, K, Matsubara, E, 90190496, 00111922, 40165783, 90173864, Matsubara, S, Yoshino, H, Yamamoto, Y, Oshima, K, Matsuoka, H, Matsumoto, K, Ishikawa, K, and Matsubara, E

Published
2005

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