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711 results on '"Ohmiya, Hirohisa"'

109. Dehydrative Allylation between Aldehydes and Allylic Alcohols through Synergistic N‐Heterocyclic Carbene/Palladium Catalysis.

Author

Haruki, Hiroki, Yasuda, Shigeo, Nagao, Kazunori, and Ohmiya, Hirohisa

Subjects
ALLYLATION, ALDEHYDES, ALLYL alcohol, CARBENES, PALLADIUM catalysts
Abstract

Dehydrative allylation between widely available aldehydes and allylic alcohols to afford β,γ‐unsaturated ketones was enabled by a synergistic merger of a thiazolium N‐heterocyclic carbene catalyst and a palladium‐bisphosphine catalyst. Dehydrative allylation between widely available aldehydes and allylic alcohols to afford β,γ‐unsaturated ketones was enabled by a synergistic merger of a thiazolium N‐heterocyclic carbene catalyst and a palladium‐bisphosphine catalyst. [ABSTRACT FROM AUTHOR]

Published
2019
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111. Synergistic palladium/copper-catalyzed Csp3–Csp2 cross-couplings using aldehydes as latent α-alkoxyalkyl anion equivalents.

Author

Takeda, Mitsutaka, Yabushita, Kenya, Yasuda, Shigeo, and Ohmiya, Hirohisa

Subjects
ALDEHYDES, PALLADIUM, ACTIVITY of copper catalysts
Abstract

The first Csp3–Csp2 cross-coupling using aldehydes as latent α-alkoxyalkyl anion equivalents has been achieved. The synergistic palladium/copper-catalyzed reaction of aromatic aldehydes and aryl bromides with a silylboronate afforded the three-component coupling products, silyl-protected benzhydrol derivatives. The reaction pathway involves the catalytic formation of a nucleophilic α-silyloxybenzylcopper(i) species followed by its palladium-catalyzed cross-coupling with aryl bromides. [ABSTRACT FROM AUTHOR]

Published
2018
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113. Phosphine‐Catalyzed <italic>anti</italic>‐Carboboration of Alkynoates with 9‐BBN‐Based 1,1‐Diborylalkanes: Synthesis and Use of Multisubstituted γ‐Borylallylboranes.

Author

Yamazaki, Ayaka, Nagao, Kazunori, Iwai, Tomohiro, Ohmiya, Hirohisa, and Sawamura, Masaya

Subjects
ALLYLATION, ORGANOCATALYSIS, ALDIMINES
Abstract

Abstract: Trialkylphosphine organocatalysis has enabled the regioselective anti‐carboboration of alkynoates with 9‐BBN‐based 1,1‐diborylalkanes to produce secondary allylboranes with β‐alkoxycarbonyl and γ‐boryl substituents. The utility of the densely functionalized allylboranes was demonstrated by the highly diastereoselective allylation of N‐(trimethylsilyl)aldimines to produce homoallylamines containing tertiary allylborane and acrylate moieties. [ABSTRACT FROM AUTHOR]

Published
2018
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114. N-Heterocyclic Carbene-Catalyzed Radical Relay Enabling Vicinal Alkylacylation of Alkenes

Author

Ishii, Takuya, Ota, Kenji, Nagao, Kazunori, and Ohmiya, Hirohisa

Abstract

The N-heterocyclic carbene-catalyzed radical relay enables the vicinal alkylacylation of styrenes, acrylates and acrylonitrile using aldehydes and tertiary alkyl carboxylic acid-derived redox-active esters. This protocol introduces tertiary alkyl groups and acyl groups to C–C double bonds with complete regioselectivity to produce functionalized ketone derivatives. The radical relay mechanism involves single electron transfer from the enolate form of a Breslow intermediate and radical addition of the resultant alkyl radical to the alkene followed by radical–radical coupling.

Published
2024
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115. Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

Author

Wakamatsu, Takamichi, Nagao, Kazunori, Ohmiya, Hirohisa, Sawamura, Masaya, Wakamatsu, Takamichi, Nagao, Kazunori, Ohmiya, Hirohisa, and Sawamura, Masaya

Abstract

A copper-catalyzed conjugate addition of alkylboron compounds (alkyl-9-BBN, prepared by hydroboration of alkenes with 9-BBN-H) to alkynoates to form beta-disubstituted acrylates is reported. The addition occurred in a formal syn-hydroalkylation mode. The syn stereoselectivity was excellent regardless of the substrate structure. A variety of functional groups were compatible with the conjugate addition.

Published
2015

116. Synthesis of 1,1-Diborylalkenes through a Bronsted Base Catalyzed Reaction between Terminal Alkynes and Bis(pinacolato)diboron

Author

Morinaga, Akira, Nagao, Kazunori, 1000040508876, Ohmiya, Hirohisa, Sawamura, Masaya, Morinaga, Akira, Nagao, Kazunori, 1000040508876, Ohmiya, Hirohisa, and Sawamura, Masaya

Abstract

A method for the synthesis of 1,1-diborylalkenes through a Bronsted base catalyzed reaction between terminal alkynes and bis(pinacolato)diboron has been developed. The procedure allows direct synthesis of functionalized 1,1-diborylalkenes from various terminal alkynes including propiolates, propiolamides, and 2-ethynylazoles.

Published
2015

137. Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold-triethynylphosphine complex : Construction of azepine frameworks by 7-exo-dig cyclization

Author

Ito, Hideto, Harada, Tomoya, Ohmiya, Hirohisa, Sawamura, Masaya, Ito, Hideto, Harada, Tomoya, Ohmiya, Hirohisa, and Sawamura, Masaya

Abstract

The gold-catalyzed, seven-membered ring forming, intramolecular hydroamination of alkynic sulfonamides has been investigated. The protocol, with a semihollow-shaped triethynylphosphine as a ligand for gold, allowed the synthesis of a variety of azepine derivatives, which are difficult to access by other methods. Both alkynic sulfoamides with a flexible linear chain and the benzene-fused substrates underwent 7-exo-dig cyclization to afford the nitrogen-containing heterocyclic seven-membered rings, such as tetrahydroazepine and dihydrobenzazepine, in good yields.

Published
2011

138. Protecting-Group-Free Route to Hydroxylated Pyrrolidine and Piperidine Derivatives through Cu(I)-Catalyzed Intramolecular Hydroamination of Alkenes

Author

Ohmiya, Hirohisa, Yoshida, Mika, 1000040202105, Sawamura, Masaya, Ohmiya, Hirohisa, Yoshida, Mika, 1000040202105, and Sawamura, Masaya

Abstract

An efficient approach to hydroxylated pyrrolidine and piperidine derivatives through the intramolecular hydroamination catalyzed by a Cu(I)-Xantphos system is described. The transformation allows for the short synthesis of N-alkylated azasugars without a protection/deprotection event of the hydroxy groups.

Published
2010

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