論文 - 河内　卓彌

Palladium-Catalyzed Electrochemical Iodination of 1-Arylpyridine N-Oxides

Zhou H., Miyasaka M., Wang Y.H., Kochi T., Kakiuchi F.

Journal of Organic Chemistry （Journal of Organic Chemistry）  2023年

ISSN  00223263

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The palladium-catalyzed C-H iodination of 1-arylpyridine N-oxides proceeded under electrochemical oxidation conditions using I2 as an iodine source. The reaction of isoquinoline N-oxides possessing various para- or meta-substituted aryl groups at the 1-position proceeded to give the corresponding iodination products. Electron-donating groups on the aryl group facilitated the reaction to give relatively high yields of the product. The reaction was also found to be applicable to 2-aryl-3-picoline N-oxides.

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Conformational Isomerization as a Process to Determine Selectivity over Reaction Pathways: Effect of Alkene Rotation in Chain Walking via Cis Alkene Intermediates

Muto K., Hatanaka M., Kakiuchi F., Kochi T.

Journal of Organic Chemistry （Journal of Organic Chemistry）  89 （ 7 ） 4712 - 4721 2024年04月

ISSN  00223263

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In organic reactions, bond-forming and bond-cleaving processes are generally considered to be more important than other processes such as conformational isomerization. We report herein an example where a conformational isomerization process, propeller-like alkene rotation, is considered to determine the selectivity over the reaction pathways. The transition state with the highest energy barrier in some alkylpalladium isomerization (chain walking) events was theoretically indicated to correspond to alkene rotation, while transition states for bond-cleaving β-hydride elimination and bond-forming migratory insertion were not even observed. It was also suggested both theoretically and experimentally that the palladium chain walking over internal carbons in alkyl chains proceeds via cis alkene intermediates rather than thermodynamically more stable trans alkene intermediates, due to their relative difficulty to undergo alkene rotation.

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Off/on Switching of Electric Current as a Strategy for One-Pot Synthesis of Bromoarylpyridines by Cross-Coupling/ C−H Bromination

Hirota Y., Fujie T., Kochi T., Kakiuchi F.

Israel Journal of Chemistry （Israel Journal of Chemistry）  64 （ 1-2 ）  2024年01月

ISSN  00212148

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An “OFF/ON” electric current switching protocol was developed as a new strategy for one-pot organic synthesis. Suzuki-Miyaura coupling of 2-bromopyridines with arylboronic acids in an electrochemical cell was performed without applying an electric current, and subsequently, the Pd-catalyzed electrochemical C−H bromination was conducted using the already-present Pd catalyst to obtain 2-(2-bromoaryl)pyridines as products. The one-pot synthesis of bromoarenes can also be achieved without adding an external Br source in the second step. Furthermore, an OFF/ON/OFF two-times switching protocol also realized the formation of an N-containing teraryl derivative.

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Rhodium-Catalyzed β-Acylalkylation of Allylbenzene Derivatives with Allyl Alcohols via C-C Bond Cleavage

Ishikawa S., Togashi R., Ueda R., Onodera S., Kochi T., Kakiuchi F.

Journal of Organic Chemistry （Journal of Organic Chemistry）  88 （ 5 ） 3313 - 3320 2023年03月

ISSN  00223263

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We report here a deallylative β-acylalkylation reaction of allylbenzene derivatives with allyl alcohols in the presence of Cp*Rh catalysts. Allylbenzenes possessing pyridyl and pyrazolyl directing groups were converted to β-aryl ketones via the cleavage of C(aryl)-C(allyl) bonds. Synthesis of a quinoline derivative from a β-aryl ketone product bearing a pyrazolyl group was also achieved.

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Palladium-Catalyzed Hydroboration/Cyclization of 1,n-Dienes

Kanno S., Kakiuchi F., Kochi T.

Journal of Organic Chemistry （Journal of Organic Chemistry）  88 （ 4 ） 2621 - 2630 2023年02月

ISSN  00223263

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While the hydroboration of alkenes is well established, the corresponding cyclization reaction of dienes remains challenging. Here, we report a new method for hydroboration/cyclization applicable to various 1,n-dienes and hydroboranes. The method features the direct synthesis of borylalkyl cyclopentanes from common 1,6-dienes, which is highlighted by syntheses of elaborated pyrrolidine cores from easily accessible diallylamines. Notably, 1,n-dienes (n > 6) also undergo five-membered ring formation, offering “remote” hydroboration/cyclization that would be otherwise difficult to achieve.

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Iron-Catalyzed Regio- and Stereoselective C-H Alkenylation of Pivalophenone Derivatives with Unsymmetric Internal Alkynes

Kitazawa Y., Kochi T., Kakiuchi F.

Journal of Organic Chemistry （Journal of Organic Chemistry）  88 （ 3 ） 1890 - 1897 2023年02月

ISSN  00223263

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Here we report an ortho-C-H alkenylation of aromatic ketones with unsymmetric internal alkynes catalyzed by an iron phosphine complex, Fe(PMe3)4. The use of a catalytic amount of PtBu3 as an additive was found to improve the product yields. The alkenylation proceeds regio- and stereoselectively to give the corresponding styrene derivatives.

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Desymmetrization of prochiral methylenes by asymmetric chain-walking cyclization using bioxazoline palladium catalysts

Shigekane M., Arai T., Tamura M., Uchida T., Kakiuchi F., Kochi T.

Tetrahedron Letters （Tetrahedron Letters）  114 2023年01月

ISSN  00404039

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We present here that the use of bioxazoline ligands improved the enantioselectivity of the palladium-catalyzed chain-walking cycloisomerization of 1,n-dienes. The new system was applied to the asymmetric chain-walking cycloisomerization of a variety of 1,n-dienes as well as asymmetric hydrosilylation/cyclization of a 1,8-diene.

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Palladium-Catalyzed Remote Diborylative Cyclization of Dienes with Diborons via Chain Walking

Kanno S., Kakiuchi F., Kochi T.

Journal of the American Chemical Society （Journal of the American Chemical Society）  143 （ 46 ） 19275 - 19281 2021年11月

ISSN  00027863

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A novel method for catalytic remote bismetalation of alkene substrates by the addition of dimetal reagents is accomplished by using chain walking. In the presence of a palladium catalyst, the reaction of various 1,n-dienes and diborons were converted into cyclopentane derivatives with two boryl groups at remote positions via facile regioselective transformation of an unactivated sp3 C-H bond to a C-B bond. Sequential construction of three distant bonds, which is difficult to achieve by any method, was accomplished for the reactions of 1,n-dienes (n ≥ 7).

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Remote Arylative Substitution of Alkenes Possessing an Acetoxy Group via β-Acetoxy Elimination

Muto K., Kumagai T., Kakiuchi F., Kochi T.

Angewandte Chemie - International Edition （Angewandte Chemie - International Edition）  60 （ 46 ） 24500 - 24504 2021年11月

ISSN  14337851

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Palladium-catalyzed remote arylative substitution was achieved for the reaction of arylboronic acids with alkenes possessing a distant acetoxy group to provide arylation products having an alkene moiety at the remote position. The use of β-acetoxy elimination as a key step in the catalytic cycle allowed for regioselective formation of unstabilized alkenes after chain walking. This reaction was applicable to various arylboronic acids as well as alkene substrates.

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Anti-Markovnikov Addition of Anilines to Aliphatic Terminal Alkynes Catalyzed by an 8-Quinolinolato Rhodium Complex

Morimoto Y., Kochi T., Kakiuchi F.

Helvetica Chimica Acta （Helvetica Chimica Acta）  104 （ 10 ）  2021年10月

ISSN  0018019X

　概要を見る

Anti-Markovnikov addition of anilines to aliphatic terminal alkynes proceeded using an 8-quinolinolato rhodium/phosphine catalyst system. The use of a strong organic base, 1,1,3,3,–tetramethylguanidine, in the catalyst system enabled the formation of the aldimine products. Substrates with various functional groups including polar groups such as a phenolic hydroxy group are applicable to the hydroamination.

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Rhodium-Catalyzed Anti-Markovnikov Hydroamination of Aliphatic and Aromatic Terminal Alkynes with Aliphatic Primary Amines

Morimoto Y., Kochi T., Kakiuchi F.

Journal of Organic Chemistry （Journal of Organic Chemistry）  86 （ 18 ） 13143 - 13152 2021年09月

ISSN  00223263

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Anti-Markovnikov hydroamination of both aliphatic and aromatic terminal alkynes with primary amines was achieved using an 8-quinolinolato rhodium catalyst to form aldimines and enamines in high yields. This catalytic system realized high functional group tolerance including hydroxy, bromo, cyano, and thioester groups.

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Deuterium-Labeling Studies on the C-H/Olefin Coupling of Aromatic Ketones Catalyzed by Fe(PMe <inf>3</inf>) <inf>4</inf>

Kimura N., Katta S., Kitazawa Y., Kochi T., Kakiuchi F.

Synthesis (Germany) （Synthesis (Germany)）  53 （ 18 ） 3383 - 3389 2021年09月

ISSN  00397881

　概要を見る

Deuterium-labeling experiments were performed for the Fe(PMe 3) 4-catalyzed C-H/olefin coupling using a deuterium-labeled aromatic ketone with various alkenes. While the reactions with a variety of alkenes provided the linear alkylation products formed via 1,2-insertion of alkene into an Fe-H bond, the reversible 2,1-insertion proceeded during the reaction highly depends on the choice of the alkene. No H/D scrambling resulting from 2,1-insertion/β-elimination was detected for the reactions with a vinylsilane and N -vinylcarbazole, but the reactions with styrenes are considered to involve rapid 2,1-insertion/ β-elimination processes to cause significant levels of H/D scrambling.

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2:1 versus 1:1 Coupling of Alkylacetylenes with Secondary Amines: Selectivity Switching in 8-Quinolinolato Rhodium Catalysis

Morimoto Y., Hamada M., Takano S., Mochizuki K., Kochi T., Kakiuchi F.

Organic Letters （Organic Letters）  23 （ 10 ） 3803 - 3808 2021年05月

ISSN  15237060

　概要を見る

Both 2:1 and 1:1 couplings of alkylacetylenes with secondary amines were achieved using 8-quinolinolato rhodium catalysts and CsF. The 2:1/1:1 selectivity was switched by choosing the reaction solvent. In DMA, an unprecedented 2:1 coupling reaction of alkylacetylenes with amines proceeded to give 2-aminodiene products. One-pot 2:1 coupling/reduction provided rapid access to various allylamines, while one-pot coupling/hydrolysis gave enones as products. In toluene, anti-Markovnikov hydroamination occurred under relatively mild conditions to give 1:1 coupling products.

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Iron-Catalyzed Ortho C-H Homoallylation of Aromatic Ketones with Methylenecyclopropanes

Kimura N., Katta S., Kitazawa Y., Kochi T., Kakiuchi F.

Journal of the American Chemical Society （Journal of the American Chemical Society）  143 （ 12 ） 4543 - 4549 2021年03月

ISSN  00027863

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We report here a C-H homoallylation reaction of aromatic ketones with methylenecyclopropanes (MCPs) only using a catalytic amount of Fe(PMe3)4. A variety of aromatic ketones and MCPs are applicable to the reaction to form ortho-homoallylated aromatic ketones selectively via regioselective scission of the three-membered rings. The homoallylated products are amenable to further elaborations, providing functionalized 1,2-dihydronaphthalenes.

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Carbon–Carbon Bond Formation via Catalytically Generated Aminocarbene Complexes: Rhodium-Catalyzed Hydroaminative Cyclization of Enynes with Secondary Amines

Takano S., Shiomi R., Morimoto Y., Kochi T., Kakiuchi F.

Angewandte Chemie - International Edition （Angewandte Chemie - International Edition）  59 （ 29 ） 11754 - 11757 2020年07月

ISSN  14337851

　概要を見る

We report a hydroaminative cyclization of enynes using phosphine-quinolinolato rhodium catalysts. The hydroaminative cyclization of 2-vinylphenylacetylene derivatives with secondary amines gives 2-aminoindenes in good yields. The reaction is considered to proceed through carbon–carbon bond formation on a catalytically generated aminocarbene ligand.

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Catalytic, Directed C-C Bond Functionalization of Styrenes

Onodera S., Togashi R., Ishikawa S., Kochi T., Kakiuchi F.

Journal of the American Chemical Society （Journal of the American Chemical Society）  142 （ 16 ） 7345 - 7349 2020年04月

ISSN  00027863

　概要を見る

A method for catalytic conversion of C(aryl)-C(alkenyl) bonds in styrene derivatives to new C-C bonds is developed. In the presence of a rhodium catalyst, the alkenyl groups of styrenes bearing a pyrazolyl directing group were efficiently converted to other carbon substituents upon reacting with various alkenes including styrenes, aliphatic alkenes, and allyl alcohols. It is also indicated that the C-C bond cleavage proceeded via a hydrometalation/β-carbon elimination pathway.

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Efficient synthesis of 3,6,13,16-tetrasubstituted-tetrabenzo[a,d,j,m]coronenes by selective C–H/C–O arylations of anthraquinone derivatives

Terai S., Sato Y., Kochi T., Kakiuchi F.

Beilstein Journal of Organic Chemistry （Beilstein Journal of Organic Chemistry）  16   544 - 550 2020年03月

ISSN  1860-5397

　概要を見る

An efficient synthesis of tetrabenzo[a,d,j,m]coronene derivatives having alkyl and alkoxy substituents at the 3, 6, 13, and 16-posi-tions was achieved based on the ruthenium-catalyzed coupling reactions of anthraquinone derivatives with arylboronates via C–H and C–O bond cleavage. The reaction sequence involving the arylation, carbonyl methylenation, and oxidative cyclization effectively provided various tetrabenzo[a,d,j,m]coronenes in short steps from readily available starting materials. Tetra-benzo[a,d,j,m]coronenes possessing two different types of substituents were obtained selectively by sequential chemoselective C–O arylation and C–H arylation. The 1H NMR spectra of the tetrabenzo[a,d,j,m]coronene product indicated its self-assembling behavior in CDCl3

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In Situ Generation of Ruthenium Carbonyl Phosphine Complexes as a Versatile Method for the Development of Enantioselective C−O Bond Arylation

Kondo H., Kochi T., Kakiuchi F.

Chemistry - A European Journal （Chemistry - A European Journal）  26 （ 8 ） 1737 - 1741 2020年02月

ISSN  09476539

　概要を見る

We report here a method for in situ generation of various ruthenium carbonyl phosphine catalysts for arylation via cleavage of inert aromatic carbon–oxygen bonds. The use of catalyst systems consisting of [RuCl2(CO)(p-cymene)], CsF, styrene, and phosphines enabled facile screening of phosphine ligands. Asymmetric C–O arylation was also achieved for atropo-enantioselective biaryl synthesis using a chiral monodentate phosphine ligand.

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Selective Monoarylation of Aromatic Ketones via C-H Bond Cleavage by Trialkylphosphine Ruthenium Catalysts

Suzuki I., Kondo H., Kochi T., Kakiuchi F.

Journal of Organic Chemistry （Journal of Organic Chemistry）  84 （ 20 ） 12975 - 12982 2019年

ISSN  00223263

　概要を見る

© 2019 American Chemical Society. A catalyst system consisting of RuHCl(CO)(PiPr3)2, CsF, and a styrene derivative was found to be applicable to selective monoarylation of aromatic ketones via ortho C-H bond cleavage. The reaction of 2′-methoxyacetophenone with arylboronates gave C-H arylation products without cleaving the ortho C-O bond. Acetophenone was also converted to monoarylation products with high selectivity. Cyclohexanone was found to be an effective solvent for the C-H arylation using the catalyst system.

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Iron-Catalyzed Ortho-Selective C−H Alkylation of Aromatic Ketones with N-Alkenylindoles and Partial Indolylation via 1,4-Iron Migration

Kimura N., Kochi T., Kakiuchi F.

Asian Journal of Organic Chemistry （Asian Journal of Organic Chemistry）  8 （ 7 ） 1115 - 1117 2019年07月

ISSN  21935807

　概要を見る

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim An ortho-selective C−H alkylation of aromatic ketones with N-alkenylindoles proceeded in the presence of just a Fe(PMe3)4 catalyst. In addition, C−H indolylation products, which are considered to be formed via 1,4-iron migration, were also observed as minor products.

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