Faculty Profiles - ISHIHARA Kazuaki

Enantioselective 1,4-Addition Reaction of α,β-Unsaturated Carboxylic Acids with Cycloalkanones Using Cooperative Chiral Amine–Boronic Acid Catalysts

Takahiro Horibe, Takashi Hazeyama, Yuto Nakata, Kazuki Takeda, Kazuaki Ishihara

Angewandte Chemie - International Edition Vol. 59 ( 39 ) page： 17256 - 17260 2020.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

An enantioselective 1,4-addition of α,β-unsaturated carboxylic acids with cycloalkanones has been developed by using chiral amine–boronic acid cooperative catalysts. In the presence of a chiral amine and boronic acid, cycloalkanones and carboxylic acids are activated as chiral enamines and mixed anhydrides, respectively. The corresponding 1,4-adducts are obtained in high yield with high enantioselectivity. Furthermore, subsequent oxylactonization of the 1,4-adducts gives spirolactones with high diastereoselectivity.

DOI： 10.1002/anie.202007639

Chemo- and Enantioselective Oxidative α-Azidation of Carbonyl Compounds

Muhammet Uyanik, Naoto Sahara, Mayuko Tsukahara, Yuhei Hattori, Kazuaki Ishihara

Angewandte Chemie - International Edition Vol. 59 ( 39 ) page： 17110 - 17117 2020.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

We report high-performance I+/H2O2 catalysis for the oxidative or decarboxylative oxidative α-azidation of carbonyl compounds by using sodium azide under biphasic neutral phase-transfer conditions. To induce higher reactivity especially for the α-azidation of 1,3-dicarbonyl compounds, we designed a structurally compact isoindoline-derived quaternary ammonium iodide catalyst bearing electron-withdrawing groups. The nonproductive decomposition pathways of I+/H2O2 catalysis could be suppressed by the use of a catalytic amount of a radical-trapping agent. This oxidative coupling tolerates a variety of functional groups and could be readily applied to the late-stage α-azidation of structurally diverse complex molecules. Moreover, we achieved the enantioselective α-azidation of 1,3-dicarbonyl compounds as the first successful example of enantioselective intermolecular oxidative coupling with a chiral hypoiodite catalyst.

DOI： 10.1002/anie.202007552

One-Pot Tandem Michael Addition/Enantioselective Conia-Ene Cyclization Mediated by Chiral Iron(III)/Silver(I) Cooperative Catalysis

Chemo‐ and Enantioselective Oxidative α‐Azidation of Carbonyl Compounds

Muhammet Uyanik, Naoto Sahara, Mayuko Tsukahara, Yuhei Hattori, Kazuaki Ishihara

Angewandte Chemie Vol. 132 ( 39 ) page： 17258 - 17265 2020.9

Takahiro Horibe, Masato Sakakibara, Rin Hiramatsu, Kazuki Takeda, Kazuaki Ishihara

Angewandte Chemie - International Edition Vol. 59 ( 38 ) page： 16470 - 16474 2020.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

The first one-pot tandem Michael addition/enantioselective Conia-ene cyclization of N-protected prop-2-yn-1-amines with 2-methylene-3-oxoalkanoates promoted by chiral iron(III)/silver(I) cooperative catalysts has been developed. Alkyl 4-methylenepyrrolidine-3-acyl-3-carboxylates, which can be transformed into β-proline derivatives, are obtained in high yield with high enantioselectivity.

DOI： 10.1002/anie.202007180

Chemoselective oxidative generation of ortho-quinone methides and tandem transformations

Halogen-Bonding Interaction between I2and N-Iodosuccinimide in Lewis Base-Catalyzed Iodolactonization Open Access

Takahiro Horibe, Yasutaka Tsuji, Kazuaki Ishihara

Organic Letters Vol. 22 ( 12 ) page： 4888 - 4892 2020.6

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society

The halogen-bonding interaction between I2 and N-iodosuccinimide (NIS) stabilized by a Lewis base (LB) has been explored. 1H NMR, nuclear Overhauser effect (NOE), and diffusion-ordered NMR spectroscopy (DOSY) suggest the generation of a 1:1:1 assembly, LB-I2-NIS. In contrast, when N-iodotrifluoromethanesulfonimide (INTf2) is used instead of NIS, LB-I5+-LB is generated. On the basis of these results in combination with density functional theory (DFT) calculations, we propose a mechanism for the formation of I2-NIS and the subsequent generation of an active iodinating species LB-I+.

DOI： 10.1021/acs.orglett.0c01735

One-pot Michael addition-enantioselective Conia-ene cyclization tandem reaction induced through chiral iron(III)-silver(I) cooperative catalysis Invited Reviewed

Takahiro Horibe, Masato Sakakibara, Rin Hiramatsu, Kazuki Takeda, Kazuaki Ishihara

Angew. Chem. Int. Ed. 2020.6

Muhammet Uyanik, Kohei Nishioka, Ryutaro Kondo, Kazuaki Ishihara

Nature Chemistry Vol. 12 ( 4 ) page： 353 - + 2020.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Nature Research

ortho-Quinone methides are useful transient synthetic intermediates in organic synthesis. These species are most often generated in situ by the acid- or base-mediated transformation of phenols that have been pre-functionalized at a benzylic position, or by biomimetic oxidation of the corresponding ortho-alkylphenols with metal oxidants or transition-metal complexes. Here we describe a method for the transition-metal-free oxidative generation of o-QMs from ortho-alkylarenols, using hypoiodite catalysis under nearly neutral conditions, which can then be applied in one-pot tandem reactions. This method for the chemoselective oxidative generation of ortho-quinone methides may prove superior to previous methods with respect to environmental issues and scope, and can be applied to various tandem reactions such as inter- or intramolecular [4 + 2] cycloaddition, oxa-6π-electrocyclization, conjugate addition and spiroepoxidation. [Figure not available: see fulltext.].

DOI： 10.1038/s41557-020-0433-4

Visual Feedback Control of a Rat Ankle Angle Using a Wirelessly Powered Two-Channel Neurostimulator Open Access

Takeuchi, M; Watanabe, K; Ishihara, K; Miyamoto, T; Tokutake, K; Saeki, S; Aoyama, T; Hasegawa, Y; Kurimoto, S; Hirata, H

SENSORS Vol. 20 ( 8 ) 2020.4

Cationic Iron(III) Salt as an Initiator for Radical Cation-induced [4+2] Cycloaddition

Takahiro Horibe, Shuhei Ohmura, Kei Katagiri, Kazuaki Ishihara

Asian Journal of Organic Chemistry Vol. 9 ( 3 ) page： 395 - 398 2020.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

We developed a cationic iron(III) salt initiator for radical cation-induced [4+2] cycloaddition. Fe(OTf)3 [or Fe(ClO4)3] behaves as a highly active oxidant for both electron-deficient and electron-rich dienophiles. The scope of substrates is much broader than with FeCl3 reported previously. With highly active Fe(OTf)3, we demonstrate a formal total synthesis of Heitziamide A.

DOI： 10.1002/ajoc.201900749

Radical-Cation-Induced Crossed [2+2] Cycloaddition of Electron-Deficient Anetholes Initiated by Iron(III) Salt Open Access

Takahiro Horibe, Kei Katagiri, Kazuaki Ishihara

Advanced Synthesis and Catalysis Vol. 362 ( 4 ) page： 960 - 963 2020.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

Radical cation-induced crossed [2+2] cycloaddition of electron-deficient anetholes was developed with the use of Fe(OTf)3 as an initiator. Various 1,2-diarylcyclobutanes can be synthesized in high yields with high diastereoselectivity from electron-deficient anetholes, which have been less explored using conventional methods. This practical reaction system can be used for a decagram-scale reaction (12 gram), in which the resulting product can be transformed to 1,2-dicarbonyl compounds. (Figure presented.).

DOI： 10.1002/adsc.201901337

Open Access