Papers - Miyamoto, Kazunori

Decarboxylative Bromination of Sterically Hindered Carboxylic Acids with Hypervalent Iodine(III) Reagents

Ayumi Watanabe, Kenta Koyamada, Kazunori Miyamoto, Junichiro Kanazawa, Masanobu Uchiyama

Organic Process Research & Development (American Chemical Society ({ACS}))  24 ( 7 ) 1328 - 1334 2020.07

ISSN  10836160

　View Summary

Sterically hindered three-dimensional (3D) alkyl halides are promising precursors for various reactions; however, they are difficult to synthesize via conventional reactions. We present an efficient and practical method for decarboxylative bromination of sterically hindered 3D aliphatic carboxylic acids using commercially available (diacetoxyiodo)benzene and potassium bromide, one of the most stable and cheapest bromine sources in nature. The present method features a metal-free/Br2-free system, mild reaction conditions, one-pot operation under air at room temperature, wide functional group compatibility, and gram-scale synthetic capability. This highly efficient reaction cleanly converts a broad range of carboxylic acids, the most inexpensive and readily available sources of highly strained/naturally occurring/drug-related scaffolds, into the corresponding alkyl bromides in good to high yields.

• Access to Document (DOI)

Rhodium-Catalyzed Highly Diastereo- and Enantioselective Synthesis of a Configurationally Stable S-Shaped Double Helicene-Like Molecule.

Suzuka Kinoshita, Ryota Yamano, Yu Shibata, Yusuke Tanaka, Kyoichi Hanada, Takashi Matsumoto, Kazunori Miyamoto, Atsuya Muranaka, Masanobu Uchiyama, Ken Tanaka

Angewandte Chemie (International ed. in English) 59 ( 27 ) 11020 - 11027 2020.06

ISSN  14337851

　View Summary

An S-shaped double helicene-like molecule (>99 % ee), possessing stable helical chirality, has been synthesized by the rhodium(I)/difluorphos complex-catalyzed highly diastereo- and enantioselective intramolecular double [2+2+2] cycloaddition of a 2-naphthol- and benzene-linked hexayne. The collision between two terminal naphthalene rings destabilizes the helical chirality of the S-shaped double helicene-like molecule, but the introduction of two additional fused benzene rings significantly increases the configurational stability. Thus, no epimerization and racemization were observed even at 100 °C. The enantiopure S-shaped double helicene-like molecule forms a trimer through the multiple C-H⋅⋅⋅π and C-H⋅⋅⋅O interactions in the solid-state. The trimers stack to form columnar packing structures, in which neighboring stacks have opposite dipole directions. The accumulation of helical structures in the same direction in the S-shaped double helicene-like molecule enhanced the chiroptical properties.

• Access to Document (DOI)

BF3-Catalyzed Skeletal Rearrangement of 7-En-2-ynones to endo-Type Cyclic Dienes

Daisuke Sato, Yuichiro Watanabe, Keiichi Noguchi, Junichiro Kanazawa, Kazunori Miyamoto, Masanobu Uchiyama, Akio Saito

Organic Letters (American Chemical Society ({ACS}))  22 ( 11 ) 4063 - 4067 2020.06

ISSN  15237060

　View Summary

Transition-metal-catalyzed cycloisomerization reactions with skeletal rearrangement of 1,n-enynes to afford cyclic dienes (particularly exo-cyclization products) have been well studied. However, there are few reports on the nonmetal-catalyzed skeletal rearrangement of enynes and skeletal rearrangement of electron-deficient enynes such as n-en-2-ynones. Here, we describe BF3·MeCN-catalyzed synthesis of 3-alkylidenecyclohexenes from 7-en-2-ynones, representing the first nonmetal-catalyzed skeletal rearrangement of 1,6-enynes to endo-type cyclic dienes.

• Access to Document (DOI)

Shelf-Stable (E)- and (Z)-Vinyl-λ3-chlorane: A Stereospecific Hyper-vinylating Agent

Yuichiro Watanabe, Taisei Takagi, Kazunori Miyamoto, Junichiro Kanazawa, Masanobu Uchiyama

Organic Letters (American Chemical Society ({ACS}))  22 ( 9 ) 3469 - 3473 2020.05

ISSN  15237060

　View Summary

We report the first stereoselective synthesis of stable (E)- A nd (Z)-β-chlorovinyl-λ3-chlorane via direct mesitylation of 1,2-dichloroethylene with mesityldiazonium tetrakis(pentafluorophenyl)borate under mild reaction conditions. The structure of the (E)-vinyl-λ3-chlorane was established by single-crystal X-ray analysis. Because of the enormously high leaving group ability of the aryl-λ3-chloranyl group, vinyl-λ3-chloranes undergo not only SNVσ-type reaction with extremely weak nucleophiles such as perfluoroalkanesulfonate, iodobenzene, and aromatic hydrocarbons but also coupling with phenylcopper(I) species.

• Access to Document (DOI)

Lipshutz-type bis(amido)argentates for directed ortho argentation

Noriyuki Tezuka, Keiichi Hirano, Andrew J. Peel, Andrew E. H. Wheatley, Kazunori Miyamoto, Masanobu Uchiyama

Chemical Science (Royal Society of Chemistry ({RSC}))  11 ( 7 ) 1855 - 1861 2020.02

ISSN  20416520

　View Summary

Bis(amido)argentate (TMP)2Ag(CN)Li2 (3, TMP-Ag-ate; TMP = 2,2,6,6-tetramethylpiperidido) was designed as a tool for chemoselective aromatic functionalization via unprecedented directed ortho argentation (DoAg). X-Ray crystallographic analysis showed that 3 takes a structure analogous to that of the corresponding Lipshutz cuprate. DoAg with this TMP-Ag-ate afforded multifunctional aromatics in high yields in processes that exhibited high chemoselectivity and compatibility with a wide range of functional groups. These included organometallics- A nd transition metal-susceptible substituents such as methyl ester, aldehyde, vinyl, iodo, (trifluoromethanesulfonyl)oxy and nitro groups. The arylargentates displayed good reactivity with various electrophiles. Chalcogen (S, Se, and Te) installation and azo coupling reactions also proceeded efficiently.

• Access to Document (DOI)

Chennat-Type Synthesis of 1,4-Dihydropyridine Derivatives in Water: Role of a Hydrogen-Bonding Network

Shigeki Isomura, Mayu Anzai, Chieka Kobayashi, Yoshinori Okuno, Kazunori Miyamoto, Masanobu Uchiyama, Yasuo Sato

ChemistrySelect (Wiley-Blackwell)  5 ( 6 ) 2075 - 2077 2020.02

ISSN  2365-6549

　View Summary

An environmentally benign Chennat-type synthesis of 4-aryl-1,4-dihydropyridine-3,5-dicarboxylic acid dimethyl esters was achieved by heating aldehyde, methyl propiolate and an amine salt in water. Excess amine salt accelerated the reaction, while stoichiometric amounts of reagents resulted in lower yield. Various 1,4-dihydropyridine (1,4-DHP) derivatives, some of which would be difficult to synthesize in organic solvents, could be obtained in up to 74 % isolated yield. The reaction utilizes a hydrogen-bonding network with water to accelerate hydroxyl group elimination from the reaction intermediate. Free amine and protons in water might be act as a nucleophile and electrophilic catalyst, respectively.

• Access to Document (DOI)

Practical Synthesis of Ethynyl(phenyl)-λ3-Iodane Using Calcium Carbide as an Ethynyl Group Source

Takahiro Hashishin, Taisei Osawa, Kazunori Miyamoto, Masanobu Uchiyama

Frontiers in Chemistry (Frontiers Media S.A.)  8 2020.02

ISSN  2296-2646

　View Summary

Stannylation of calcium carbide followed by Sn–hypervalent iodine(III) exchange reaction cleanly afforded the electrophilic ethynylating agent ethynyl(phenyl)-λ3-iodane in high yield. This two-step method uses very inexpensive materials and is readily operable without any special precautions.

• Access to Document (DOI)

Silaboration of [1.1.1]Propellane: A Storable Feedstock for Bicyclo[1.1.1]pentane Derivatives

Masaki Kondo, Junichiro Kanazawa, Tomohiro Ichikawa, Takumi Shimokawa, Yuki Nagashima, Kazunori Miyamoto, Masanobu Uchiyama

Angewandte Chemie (Wiley)  132 ( 5 ) 1986 - 1990 2020.01

• Access to Document (DOI)

Silaboration of [1.1.1]Propellane: A Storable Feedstock for Bicyclo[1.1.1]pentane Derivatives

Kondo M., Kanazawa J., Ichikawa T., Shimokawa T., Nagashima Y., Miyamoto K., Uchiyama M.

Angewandte Chemie - International Edition 59 ( 5 ) 1970 - 1974 2020.01

ISSN  14337851

　View Summary

The silaboration of [1.1.1]propellane enables direct introduction of B and Si functional groups onto the bicyclo[1.1.1]pentane (BCP) scaffold in high yield under mild, additive-free conditions. The silaborated BCP can be obtained on a gram-scale in a single step without the need for column-chromatographic purification, and is storable and easy to handle, providing a versatile synthetic intermediate for BCP derivatives. We also describe various conversions of the C−B/C−Si bonds on the BCP scaffold, including development of a modified Suzuki–Miyaura cross-coupling reaction at the highly sterically hindered bridgehead sp3 carbon center of the BCP skeleton using a combination of highly activated BCP boronic esters, copper(I) oxide, and a PdCl2(dppf) catalyst system.

• Access to Document (DOI)

Silaboration of [1.1.1]Propellane: A Storable Feedstock for Bicyclo[1.1.1]pentane Derivatives

Masaki Kondo, Junichiro Kanazawa, Tomohiro Ichikawa, Takumi Shimokawa, Yuki Nagashima, Kazunori Miyamoto, Masanobu Uchiyama

Angewandte Chemie International Edition (Wiley)  59 ( 5 ) 1970 - 1974 2020.01

• Access to Document (DOI)

Alkynylboration Reaction Leading to Boron-Containing π-Extended cis-Stilbenes as a Highly Tunable Fluorophore

Marina Nogami, Keiichi Hirano, Kensuke Morimoto, Masaru Tanioka, Kazunori Miyamoto, Atsuya Muranaka, Masanobu Uchiyama

Organic Letters (American Chemical Society ({ACS}))  21 ( 9 ) 3392 - 3395 2019.05

ISSN  15237060

　View Summary

An unprecedented boron-containing fluorophore, π-extended cis-stilbene, obtained via alkynylboration reaction of alkynamide is reported. Boron-containing π-extended cis-stilbenes emit fluorescence with high quantum yields in the solid state and exhibit aggregation-induced emission enhancement. The broad substrate scope of the alkynylboration reaction offers facile access to electronically diverse structures, enabling fine-tuning of light absorption/emission characteristics. The boron-containing π-extended cis-stilbene with a diphenylamino group displays solvatofluorochromism via an intramolecular charge-transfer transition.

• Access to Document (DOI)

Diaryl-λ3-chloranes: Versatile Synthesis and Unique Reactivity as Aryl Cation Equivalent

Misuzu Nakajima, Kazunori Miyamoto, Keiichi Hirano, Masanobu Uchiyama

Journal of the American Chemical Society (American Chemical Society ({ACS}))  141 ( 16 ) 6499 - 6503 2019.04

ISSN  00027863

　View Summary

We have developed a versatile, high-yield synthesis of diarylchloroniums/λ3-chloranes through the reaction of various chloroarenes with readily prepared mesityldiazonium tetrakis(pentafluorophenyl)borate under mild conditions. The scope of the reaction is broad, including ArCl, ArBr, and ArI. The diarylchloroniums/λ3-chloranes prepared here show unique reactivity in various respects, enabling intermolecular electrophilic arylation reaction of weak nucleophiles, and chlorane-halogane exchange reaction.

• Access to Document (DOI)

Stable Thiele’s Hydrocarbon Derivatives Exhibiting Near-Infrared Absorption/Emission and Two-Step Electrochromism

Yuta Okamoto, Masaru Tanioka, Atsuya Muranaka, Kazunori Miyamoto, Tetsuya Aoyama, Xingmei Ouyang, Shinichiro Kamino, Daisuke Sawada, Masanobu Uchiyama

Journal of the American Chemical Society (American Chemical Society ({ACS}))  140 ( 51 ) 17857 - 17861 2018.12

ISSN  00027863

　View Summary

We report synthesis and characterization of near-infrared (NIR)-absorbing/emitting Thiele's hydrocarbon derivatives, in which four aryl groups are bridged to a quinodimethane skeleton. The quinoid structure of the bridged-tetra-aryl-p-quinodimethanes (BTAQs) was confirmed by spectroscopic, X-ray crystallographic, and computational methods. Although quinodimethane derivatives with a small HOMO-LUMO energy gap often exhibit biradical character, BTAQs showed no biradical character. Instead, they exhibited two-step near-infrared electrochromism. The donor/acceptor properties of the aryl groups were found to play a key role in the unique properties of BTAQs.

• Access to Document (DOI)

Safer Synthesis of (Diacetoxyiodo)arenes Using Sodium Hypochlorite Pentahydrate

Ayumi Watanabe, Kazunori Miyamoto, Tomohide Okada, Tomotake Asawa, Masanobu Uchiyama

The Journal of Organic Chemistry (American Chemical Society ({ACS}))  83 ( 23 ) 14262 - 14268 2018.12

ISSN  00223263

　View Summary

A practical method for the preparation of (diacetoxyiodo)arene ArI(OAc) 2 is described. The use of commercially available sodium hypochlorite pentahydrate (NaClO·5H 2 O) enabled safe, rapid, and inexpensive oxidation of iodoarenes with electron-withdrawing and -donating substituents. The method allows tandem divergent access to synthetically useful organo-λ 3 -iodanes such as hydroxyl(tosyloxy)iodobenzene, iodosylbenzene, iodonium ylide, etc.

• Access to Document (DOI)

Oxidative α‐Acetoxylation of a β‐Oxime Ester with (Diacetoxyiodo)benzene Catalyzed by ScIII Salts: An Approach to the Docetaxel Side Chain

Kazunori Miyamoto, Md. Mahbubul Hoque, Yuhki Senoh, Mohammad Idrish Ali, Hisao Nemoto, Tadakatsu Mandai

European Journal of Organic Chemistry 2018 ( 22 ) 2841 - 2845 2018.06

ISSN  1434193X

　View Summary

Hypervalent iodine(III) compounds have emerged as reagents of choice for α-oxidation of various ketones under mild reaction conditions. We report herein a simple method for α-hydroxylation of a β-oxime ester, which involves an oxidative α-acetoxylation using PhI(OAc)2 with a catalytic amount of Sc(OTf)3 or Sc2O3-TMSOTf, followed by careful hydrolysis. The scandium(III) salt serves as an excellent reusable catalyst in this system.

• Access to Document (DOI)

One‐pot Annulation for Biaryl‐fused Monocarba‐closo‐dodecaborate through Aromatic B−H Bond Disconnection

Gaku Akimoto, Mai Otsuka, Kazunori Miyamoto, Atsuya Muranaka, Daisuke Hashizume, Ryo Takita, Masanobu Uchiyama

Chemistry – An Asian Journal 13 ( 8 ) 913 - 917 2018.04

ISSN  18614728

　View Summary

We have developed a one-pot annulation reaction of monocarba-closo-dodecaborate with cyclic diaryliodonium salts to afford biaryl-fused derivatives. Aryl functionalities are introduced at both the 1-carbon and unreactive ortho-boron vertices of the “σ-aromatic” carborane cage without the need for pre-functionalization. DFT calculations revealed that the palladium-catalyzed C−B bond-formation step in this process proceeds through a concerted metalation–deprotonation (CMD)-type pathway for the B−H bond disconnection on the aromatic cage, though such bonds are generally regarded as hydridic.

• Access to Document (DOI)

N-Alkynylpyridinium Salts: Highly Electrophilic Alkyne–Pyridine Conjugates as Precursors of Cationic Nitrogen-Embedded Polycyclic Aromatic Hydrocarbons

Naoyuki Toriumi, Norihito Asano, Kazunori Miyamoto, Atsuya Muranaka, Masanobu Uchiyama

Journal of the American Chemical Society (American Chemical Society ({ACS}))  140 ( 11 ) 3858 - 3862 2018.03

ISSN  00027863

　View Summary

We achieved the first synthesis of N-alkynylpyridinium salts, by reacting pyridines with alkynyl-λ3-iodanes. The N-alkynylpyridiniums exhibit highly electron-accepting character with extended π-conjugation. The electrophilic alkynyl groups were readily susceptible to Michael addition and 1,3-dipolar cycloaddition to afford various N-alkenylpyridiniums. Ring-fused pyridiniums were synthesized through intramolecular cyclization, demonstrating the utility of N-alkynylpyridiniums for the design of various electron-deficient cationic nitrogen-embedded polycyclic aromatic hydrocarbons with unique optical and electrochemical properties.

• Access to Document (DOI)

“Dumbbell”- and “Clackers”-Shaped Dimeric Derivatives of Monocarba-closo-dodecaborate

Kitazawa Y., Watanabe M., Masumoto Y., Otsuka M., Miyamoto K., Muranaka A., Hashizume D., Takita R., Uchiyama M.

Angewandte Chemie - International Edition 57 ( 6 ) 1501 - 1504 2018.02

ISSN  14337851

　View Summary

We designed, synthesized, and characterized two types of dimeric forms of monocarba-closo-dodecaborate, namely, a “dumbbell”-shaped dianion having a C−C bond and a “clackers”-shaped monoanion having an iodonium linker. The unique architectures of these anionic molecules were established by X-ray analysis. Spectroscopic analysis, DFT calculations, and reactivity experiments revealed high anionic and chemical stability of both anions, which are crucial properties for weakly coordinating anions.

• Access to Document (DOI)

“Dumbbell”‐ and “Clackers”‐Shaped Dimeric Derivatives of Monocarba‐closo‐dodecaborate

Yu Kitazawa, Mamoru Watanabe, Yui Masumoto, Mai Otsuka, Kazunori Miyamoto, Atsuya Muranaka, Daisuke Hashizume, Ryo Takita, Masanobu Uchiyama

Angewandte Chemie  2018.02

• Access to Document (DOI)

Mechanistic Study on Aryl-Exchange Reaction of Diaryl-λ3-iodane with Aryl Iodide

Yui Masumoto, Kazunori Miyamoto, Takuto Iuchi, Masahito Ochiai, Keiichi Hirano, Tatsuo Saito, Chao Wang, Masanobu Uchiyama

The Journal of Organic Chemistry (American Chemical Society ({ACS}))  83 ( 1 ) 289 - 295 2018.01

ISSN  00223263

　View Summary

Because of its hyper-leaving ability, as well as its strong oxidizing ability, diaryl(triflato)-λ3-iodane transfers one of the aryl groups to iodoarenes simply upon gentle heating (>85 °C) in nonpolar solvents. We have performed an in-depth mechanistic study of this unusual aryl transfer reaction. A combination of experimental (product analysis, kinetic study, and substituent effects) and density functional theoretical approaches revealed that the reaction proceeds through a concerted bimolecular transition state, in which ipso-carbon binds loosely to both iodine centers. We also evaluated electronic effects on the thermodynamic stability of diaryl-λ3-iodanes.

• Access to Document (DOI)