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Papers - Yamada, Toru

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Lewis Acid-catalyzed Decarboxylative Cyanation of Cyclic Enol Carbonates ®Access to Multi-substituted ¢-Ketonitriles®

Yokoyama H., Dokai Y., Kimaru N., Saito K., Yamada T.

Chemistry Letters (Chemistry Letters) 51 ( 4 ) 469 - 472 2022.04

Joint Work, ISSN 03667022

A Lewis acid-catalyzed decarboxylative substitution reaction of cyclic enol carbonates with a cyanation reagent was developed to give ¢-ketonitriles in good yield. It is proposed that the reaction proceeds through an oxyallyl cation intermediate or its equivalent. Interestingly, cyanation selectively took place at the more hindered site of the intermediate to afford a multi-substituted ¢-ketonitrile. This regioselectivity was observed by the cyanation of a wide range of substrates and is discussed in terms of the reaction mechanism.

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Microwave-specific enhancement of nazarov cyclization

Kubota Y., Kawanori T., Sawada T., Saito K., Yamada T.

Chemistry Letters (Chemistry Letters) 50 ( 1 ) 144 - 146 2021.01

Research paper (scientific journal), Joint Work, Accepted, ISSN 03667022

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Stereoselective amination: Via vinyl-silver intermediates derived from silver-catalyzed carboxylative cyclization of propargylamine

Sadamitsu Y., Saito K., Yamada T.

Chemical Communications (Chemical Communications) 56 ( 66 ) 9517 - 9520 2020.08

ISSN 13597345

© The Royal Society of Chemistry. The stereoselective synthesis of aminovinyloxazolidinones based on the electrophilic amination of a vinyl-silver intermediate, generated by silver-catalyzed carbon dioxide incorporation on a propargyl amine, was achieved. The geometry of the aminated product was determined by a single crystal X-ray analysis and NOE measurement and it was elucidated that the geometry was proved to be opposite to the geometry predicted from the previous silver-catalyzed carbon dioxide fixation on a propargyl amine derivative. This unexpected stereoselectivity could be successfully explained by a radical mechanism. This journal is

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Thermal decarboxylative Nazarov cyclization of cyclic enol carbonates involving chirality transfer

Kozuma A., Komatsuki K., Saito K., Yamada T.

Chemistry Letters (Chemistry Letters) 49 ( 1 ) 60 - 63 2020

Research paper (scientific journal), Joint Work, Accepted, ISSN 03667022

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Silver-Catalyzed Carbon Dioxide Fixation on Alkynylindenes

Okumura A., Chuang P.Y., Saito K., Yamada T.

Organic Letters (Organic Letters) 2020

ISSN 15237060

© The synthesis of polycyclic indene derivatives via silver-catalyzed carbon dioxide fixation on 2-alkynylindene derivatives was achieved by nucleophilic addition of the indenyl anion to carbon dioxide involving carbon-carbon bond formation and subsequent intramolecular cyclization to the alkyne part activated by a silver catalyst. This cascade process could be applied to various substrates to obtain the corresponding products in high yields. The endo/exo selectivity of the cyclization could be controlled by the steric or electronic effect of the substituents on the substrates, and 6-endo-selective cyclization was realized to afford α-pyrone-fused indenes.

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Decarboxylative Nazarov Cyclization-Based Chirality Transfer for Asymmetric Synthesis of 2-Cyclopentenones

Komatsuki K., Kozuma A., Saito K., Yamada T.

Organic Letters (Organic Letters) 21 ( 17 ) 6628 - 6632 2019.09

ISSN 15237060

© 2019 American Chemical Society. Asymmetric synthesis of 2-cyclopentenones was achieved by chirality transfer based on Lewis acid catalyzed decarboxylative Nazarov cyclization of optically active cyclic enol carbonates, which are prepared by silver-catalyzed carbon dioxide incorporation into optically pure propargyl alcohols. The stereochemistry at the 4,5-positions of the 2-cyclopentenones was cleanly constructed by reflecting the stereochemistry of the starting materials. This method could be applied to various substrates to obtain the corresponding products in high yields with highly efficient chirality transfer.

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Microwave specific effect on catalytic enantioselective reactions

Yamada T.

Asia-Pacific Microwave Conference Proceedings, APMC (Asia-Pacific Microwave Conference Proceedings, APMC) 2018-November 1627 - 1629 2019.01

Research paper (scientific journal), Joint Work, Accepted, ISSN 9784902339451

© 2018 IEICE The microwave specific effect was investigated on the catalytic enantioselective reactions; atropo-enantiveselective ring-opening reaction of biaryl lactones and enantioselective Claisen rearrangement reaction. These reactions were efficiently enhanced with microwave irradiation under reaction temperature control, thought any loss of the enantioselectivities were not detected. It was also found that the racemization rate of the atropo-optically active biaryl lactone was enhanced by microwave irradiation. As these observations could not be explained by the simple thermal effect, microwave specific effect should be considered.

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Kolbe-Schmitt type reaction under ambient conditions mediated by an organic base

Sadamitsu Y., Okumura A., Saito K., Yamada T.

Chemical Communications (Chemical Communications) 55 ( 66 ) 9837 - 9840 2019

ISSN 13597345

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7 Silver-Catalyzed CO2 Incorporation

Yamada T., Sekine K., Sadamitsu Y., Saito K.

Silver Catalysis in Organic Synthesis (Silver Catalysis in Organic Synthesis) 407 - 438 2018.12

Research paper (scientific journal), Joint Work, Accepted, ISSN 9783527342815

Amidation reaction of carboxylic acid with formamide derivative using SO<inf>3</inf>•pyridine

Kawano S., Saito K., Yamada T.

Chemistry Letters (Chemistry Letters) 47 ( 4 ) 584 - 586 2018

Research paper (scientific journal), Joint Work, Accepted, ISSN 03667022

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Microwave-Specific Effect on Enantioselective Reactions

YAMADA TOHRU

Journal of the Jpn. Petrol. Inst. (石油学会) 61 ( 2 ) 121 - 128 2018

Research paper (scientific journal), Joint Work, Accepted, ISSN 13468804

© 2018 Office of the Federal Register. All rights reserved. Microwave irradiation is widely applied to organic synthesis. Many advantages of microwave irradiation, including drastic shortening of reaction time, suppression of side reactions, and/or higher chemical yield, have been proposed. Generally, these effects have been understood merely as a simple thermal effect, since microwave irradiation rapidly raises the temperature of the reaction mixture. However, some observed results could not be understood only by the thermal effect. Recently our group reported that several enantioselective reactions were accelerated under microwave irradiation without loss of enantioselectivity. As these extraordinary results could not be explained by the simple thermal effect, the concept of the "microwave-specific effect" should be considered. We describe our recent experimental results to elucidate the microwave-specific effect. Investigations are described on enantioselective ring-opening reactions of biaryl lactone derivatives, racemization of an optically pure biaryl lactone derivative, enantioselective Claisen rearrangement reaction, enantioselective Conia-ene reaction and ring-closing metathesis reaction. These reactions or racemization of optically pure compounds were accelerated under microwave conditions. Such reaction acceleration of enantioselective reactions was observed without loss of enantioselectivity.

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Amidation Reaction of Carboxylic Acid with Formamide Derivative Using SO3·pyridine

YAMADA TOHRU

Chem. Lett. (日本化学会) 47 584 - 586 2018