Search

Your search keyword '"Ohmiya, Hirohisa"' showing total 711 results
Start Over Author "Ohmiya, Hirohisa"
711 results on '"Ohmiya, Hirohisa"'

63. Enantiocontrol by assembled attractive interactions in copper-catalyzed asymmetric direct alkynylation of α-ketoesters with terminal alkynes: OH···O/sp3-CH···O two-point hydrogen bonding combined with dispersive attractions† †Electronic supplementary information (ESI) available: Representative experimental procedures, spectroscopic data, and computational details. See DOI: 10.1039/c8sc00527c

Author

Schwarzer, Martin C., Fujioka, Akane, Ishii, Takaoki, Ohmiya, Hirohisa, Mori, Seiji, and Sawamura, Masaya

Subjects
Chemistry
Abstract

A chiral copper catalyst selects enantiofaces by assembled attractive interactions., Copper-catalyzed asymmetric direct alkynylation of α-ketoesters with terminal alkynes with chiral prolinol–phosphine ligands, most preferably (αR,2S)-1-(2-dicyclohexylphosphinobenzyl)-α-neopentyl-2-pyrrolidinemethanol, afforded various enantioenriched chiral propargylic tertiary alcohols. Quantum-chemical calculations using the BP86 density functional including Grimme's empirical dispersion correction [DF-BP86-D3(BJ)-PCM(tBuOH)/TZVPP//DF-BP86-D3(BJ)/SVP] show the occurrence of OH···O/sp3-CH···O two-point hydrogen bonding between the chiral ligand and the carbonyl group of the ketoester in the stereo-determining transition states. Combined with the hydrogen-bonding interactions orienting the ketoester substrate, dispersive attractions between the chiral ligand (P-cyclohexyl groups) and the ketoester in the favored transition states, rather than steric repulsions in the disfavored transition state explain the enantioselectivity of the asymmetric copper catalysis.

Published
2018

64. Asymmetric Synthesis of beta-Lactams through Copper-Catalyzed Alkyne-Nitrone Coupling with a Prolinol-Phosphine Chiral Ligand

Author

Takayama, Yurie, Ishii, Takaoki, Ohmiya, Hirohisa, Iwai, Tomohiro, Schwarzer, Martin C., Mori, Seiji, Taniguchi, Tohru, Monde, Kenji, and Sawamura, Masaya

Subjects
nitrones, copper, asymmetric catalysis, cooperative catalysis, beta-lactam
Abstract

Prolinol-phosphine chiral ligands enabled highly enantioselective copper-catalyzed intermolecular alkyne-nitrone coupling (Kinugasa reaction) to produce 1,3,4-trisubstituted chiral beta-lactams. A high level of enantiocontrol was achieved not only with aryl-or alkenylacetylenes but also with alkylacetylenes, which were important but unfavorable substrates in the previously reported protocols. Two-point hydrogen bonding between the chiral ligand and the nitrone oxyanion consisting of O-H center dot center dot center dot O and C(sp(3)) H center dot center dot center dot O hydrogen bonds is proposed.

Published
2017

65. Direct Photoexcitation of Borate Enabling Minisci Reaction.

Author

Kemmochi, Marin, Miyamoto, Yusuke, Sumida, Yuto, and Ohmiya, Hirohisa

Subjects
ALKYL radicals, METHYL radicals, BORATES, VISIBLE spectra, HETEROARENES, ALKYLATION, PHOTOEXCITATION
Abstract

The photoexcitable borate enabling Minisci C−H alkylation of heteroarene has been described. This protocol using alkylborate only needed O2 and visible light, which provides a considerably clean system. The direct photoexcitation of alkylborate allowed the generation of tertiary, secondary, and primary‐alkyl radical including methyl radical. This light‐driven Minisci reaction gave a choice for the functionalization of heteroarenes. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

79. Copper-Catalyzed gamma-Selective and Stereospecific Allylic Cross-Coupling with Secondary Alkylboranes

Author

Yasuda, Yuto, Nagao, Kazunori, Shido, Yoshinori, Mori, Seiji, Ohmiya, Hirohisa, and Sawamura, Masaya

Subjects
copper catalysis, secondary alkylborane, allylic substitution, coupling, stereoselectivity
Abstract

The scope of the copper-catalyzed coupling reactions between organoboron compounds and allylic phosphates is expanded significantly by employing triphenylphosphine as a ligand for copper, allowing the use of secondary alkylboron compounds. The reaction proceeds with complete gamma-E-selectivity and preferential 1,3-syn stereoselectivity. The reaction of gamma-silicon-substituted allylic phosphates affords enantioenriched alpha-stereogenic allylsilanes.

Published
2015

80. Molecular Field Analysis Using Computational-Screening Data in Asymmetric N-Heterocyclic Carbene-Copper Catalysis toward Data-Driven In SilicoCatalyst Optimization

Author

Mukai, Masakiyo, Nagao, Kazunori, Yamaguchi, Shigeru, and Ohmiya, Hirohisa

Abstract

A molecular-field-based regression analysis using computational screening data for N-heterocyclic carbene (NHC)-Cu-catalyzed asymmetric carbonyl additions of a silylboronate to aldehydes is reported. A computational screening was performed to collect enantioselectivity data (ΔΔG‡: energy differences between the transition states leading to each enantiomer) via transition-state (TS) calculations using density functional theory (DFT) methods. A molecular field analysis (MFA) was carried out using the obtained calculated ΔΔG‡values and TS structures (30 samples in total). Important structural information for enantioselectivity extracted by the MFA was visualized on the TS structures, which provided insight into an asymmetric induction mechanism. Based on the obtained information, chiral NHC ligands were designed, which showed improved enantioselectivity in these carbonyl additions (designed ligands: up to 96% ee, initial training samples: up to 73% ee).A molecular field analysis using computational-screening data and the corresponding transition-state structures with a relatively small dataset (30 samples) enabled the regression-based data-driven design of chiral NHC ligands with improved enantioselectivity for the Cu-catalyzed carbonyl addition of a silylboronate.

Published
2022
Full Text
View/download PDF

89. Copper-Catalyzed Enantioselective Coupling between Allylboronates and Phosphates Using a Phenol-Carbene Chiral Ligand: Asymmetric Synthesis of Chiral Branched 1,5-Dienes

Author

Yasuda, Yuto, 1000040508876, Ohmiya, Hirohisa, 1000040202105, Sawamura, Masaya, Yasuda, Yuto, 1000040508876, Ohmiya, Hirohisa, 1000040202105, and Sawamura, Masaya

Abstract

Details of the Cu-catalyzed enantioselective allyl-allyl coupling reaction between allylboronates and (Z)-allylic phosphates using a new chiral N-heterocyclic carbene (NHC) ligand containing a phenolic hydroxy group are presented. The copper catalysis delivers enantioenriched chiral 1,5-dienes with a tertiary stereogenic center. Compatibility with various functional groups and the use of earth-abundant and relatively low-toxicity copper as a metal are attractive features of this protocol. The utility of the chiral phenol-NHC ligand for enantioselective copper catalysis with organoboron compounds is demonstrated and enantiodiscrimination models are discussed.

Published
2018

90. Ester-derived regioselective borylation of heteroarenes catalyzed by a silica-supported iridium complex

Author

Kawamorita, Soichiro, Ohmiya, Hirohisa, and Sawamura, Masaya

Subjects
Catalysis -- Analysis, Esters -- Chemical properties, Furans -- Chemical properties, Iridium -- Chemical properties, Pyrrole -- Chemical properties, Pyrrole -- Structure, Silica -- Chemical properties, Thiophene -- Chemical properties, Thiophene -- Structure, Biological sciences, Chemistry
Abstract

The ester-directed regioselective borylation of arenes catalyzed by a silica-supported monophosphine-Ir complex has exhibited a broad substrate scope toward heteroaromatic compounds, including thiophene, pyrrole, furan, benzothiophene, benzofuran, indole, and carbazole derivatives. The regioselectivity is complementary to the selectivities in the heteroarene C-H borylation with the dtbpy-Ir catalyst system.

Published
2010

91. Copper-catalyzed [gamma]-selective allyl-alkyl coupling between allylic phosphates and alkylboranes

Author

Ohmiya, Hirohisa, Yokobori, Umi, Makida, Yusuke, and Sawamura, Masaya

Subjects
Copper -- Chemical properties, Organoboron compounds -- Chemical properties, Organoboron compounds -- Structure, Phosphates -- Chemical properties, Chemistry
Abstract

Copper-catalyzed allyl-alkyl coupling between allylic phosphates and alkylboranes has taken place with complete [gamma]- and E-selectivities and with preferential 1,3-anti stereochemistry. The reaction has tolerated various functional groups in both the allylic phosphate and alkylborane and catalytic mechanisms are proposed that have involved transmetalation between a trialkyl(alkoxo)borate and a copper(I) complex to form an alkylcopper(I) species.

Published
2010

92. Palladium-catalyzed [gamma]-selective and stereospecific allyl-aryl coupling between acyclic allylic esters and arylboronic acids

Author

Ohmiya, Hirohisa, Makida, Yusuke, Dong Li, Tanabe, Masahito, and Sawamura, Masaya

Subjects
Acetates -- Chemical properties, Arylation -- Analysis, Organoboron compounds -- Structure, Organoboron compounds -- Chemical properties, Palladium catalysts -- Chemical properties, Sertraline -- Chemical properties, Sertraline -- Structure, Chemistry
Abstract

Palladium-catalyzed reactions with excellent [gamma]-selectivity are performed between acyclic (E)-allylic acetates and arylboronic acids to yield allyl-aryl coupling products with E-configuration. The synthetic application and the stoichiometric reactions of palladium complexes related to possible intermediates are demonstrated by an efficient synthesis of (plus)-sertraline, an antidepressant agent.

Published
2010

93. Directed ortho borylation of functionalized arenes catalyzed by a silica-supported compact phosphine-iridium system

Author

Kawamorita, Soichiro, Ohmiya, Hirohisa, Hara, Kenji, Fukuoka, Atsushi, and Sawamura, Masaya

Subjects
Benzene -- Chemical properties, Catalysis -- Analysis, Iridium -- Chemical properties, Organoboron compounds -- Chemical properties, Organoboron compounds -- Structure, Silica -- Chemical properties, Chemistry
Abstract

An immobilized monophosphine-Ir system is prepared from [[Ir(OMe)(cod)].sub.2] and a silica-supported, compact phosphine and it has shown high activities and selectivities for the borylation of aromatic C-H bonds with bis(pinacolato)diboron. This system is effective for the borylation of benzene and also for the ortho borylation of arenes with directing groups, such as ester, amide, sulfonate, acetal, alkoxymethyl, and chloro groups, under mild reaction conditions.

Published
2009

94. Palladium-catalyzed [gamma]-selective and stereospecific allyl-aryl coupling between allylic acetates and arylboronic acids

Author

Ohmiya, Hirohisa, Makida, Yusuke, Tanaka, Tatsunori, and Sawamura, Masaya

Subjects
Allylic compounds -- Chemical properties, Chirality -- Analysis, Palladium catalysts -- Chemical properties, Substitution reactions -- Analysis, Chemistry
Abstract

An air-tolerable, Pd-catalyzed [gamma]-selective and stereospecific substitution reaction between allylic acetates and arylboronic acids is described, which has produced allyl-aryl coupling products with a stereogenic center at the benzylic position. The reaction mechanism and development of more advanced catalyst system and enantioselective reactions with a chiral catalyst is being explored.

Published
2008

95. Cobalt-catalyzed regioselective dehydrohalogenation of alkyl halides with dimethylphenylsilylmethylmagnesium chloride

Author

Kobayashi, Tsuneyuki, Ohmiya, Hirohisa, Yorimitsu, Hideki, and Oshima, Koichiro

Subjects
Cobalt -- Chemical properties, Cobalt -- Structure, Magnesium compounds -- Chemical properties, Magnesium compounds -- Structure, Chemistry
Abstract

The cobalt-catalyzed highly regioselective dehydrohalogenation reaction of alkyl halides with a Grignard reagent is described. The reaction mechanism of the cobalt-catalyzed dehydrohalogenation has offered unique transformations that are otherwise difficult to attain.

Published
2008

Catalog

Books, media, physical & digital resources
See catalog results