Details of a Researcher - Miyamoto, Kazunori

Oxidation of primary aliphatic aldehydes with p- trifluoromethylphenyl(difluoro)-λ 3-bromane in dichloromethane at 0 °C afforded acid fluorides selectively in good yields, while that of aromatic aldehydes in chloroform at room temperature produced aryl difluoromethyl ethers. A larger migratory aptitude of aryl groups compared to primary alkyl groups during a 1,2-shift from carbon to an electron-deficient oxygen atom in bromane(III) Criegee-type intermediates will result in these differences in the reaction courses. © 2011 American Chemical Society.

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Synthesis and Structure of Hypervalent Diacetoxybromobenzene and Aziridination of Olefins with Imino-lambda(3)-bromane Generated in Situ under Metal-Free Conditions

Md. Mahbubul Hoque, Kazunori Miyamoto, Norihiro Tada, Motoo Shiro, Masahito Ochiai

ORGANIC LETTERS (AMER CHEMICAL SOC) 13 ( 20 ) 5428 - 5431 2011.10

Accepted, ISSN 15237060

Ligand exchange of p-CF3C6H4BrF2 with acetoxy groups using AcOH and Ac2O affords (diacetoxybromo)benzene in a high yield, which undergoes azirldination of alkenes In the presence of TfNH2 and sulfamate esters in one pot under mild conditions. The azirldination with TfNH2 proceeds stereospecifically with retention of stereochemistry of olefins at room temperature using limiting amounts of olefins under transition-metal-free conditions. The one-pot aziridination procedure using sulfamate esters can be applied to the Intramolecular versions.

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Highly regioselective amination of unactivated alkanes by hypervalent sulfonylimino-δ3-bromane

Masahito Ochiai, Kazunori Miyamoto, Takao Kaneaki, Satoko Hayashi, Waro Nakanishi

Science (American Association for the Advancement of Science (AAAS)) 332 ( 6028 ) 448 - 451 2011.04

Accepted, ISSN 00368075

Amination of alkanes has generally required metal catalysts and/or high temperatures. Here we report that simple exposure of a broad range of alkanes to N-triflylimino-δ3-bromane 1 at ambient temperature results in C-H insertion of the nitrogen functionality to afford triflyl-substituted amines in moderate to high yields. Marked selectivity for tertiary over secondary C-H bonds was observed
primary (methyl) C-H bonds were inert. Addition of hexafluoroisopropanol to inhibit decomposition of 1 dramatically improved the C-H amination efficiencies. Second-order kinetics, activation parameters (negative activation entropy), deuterium isotope effects, and theoretical calculations suggest a concerted asynchronous bimolecular transition state for the metal-free C-H amination event.

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Synthesis and Reaction of Hypervalent λ3-Iodane-Crown Ether Complexes

MIYAMOTO Kazunori

YAKUGAKU ZASSHI (The Pharmaceutical Society of Japan) 131 ( 4 ) 545 - 552 2011.04

ISSN 00316903

In this review, we show that intermolecular hypervalent I(III)…O interactions play an essential role in the complexation of organo-λ3-iodanes with crown ethers. In addition to the well-known driving force for the complexation of crown ethers, ion-dipole interaction, and hydrogen bonding interaction, our result provides a new class of interaction in supramolecular chemistry of crown ethers. Both solid state structure analysis and solution chemistry indicate that diaryl-, 1-alkenyl(phenyl)-, 1-alkynyl(phenyl)-, and hydroxy(phenyl)-λ3-iodanes form stable complexes with 18-crown-6 through hypervalent I(III)…O interactions. The complexation not only increases the stability of these hypervalent λ3-iodanes but also holds its high reactivity toward nucleophiles. The complex of hydroxy(phenyl)-λ3-iodanes with 18-crown-6 serve as versatile oxidizing agents, especially in water.

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Synthesis and Structure of Aliphatic Phenylchloronium Ylide

Masahito Ochiai, Norihiro Tada, Kazunori Miyamoto, Motoo Shiro

HETEROATOM CHEMISTRY (WILEY-BLACKWELL) 22 ( 3-4 ) 325 - 330 2011.04

Accepted, ISSN 10427163

Aliphatic phenylchloronium ylide with bis(trifluoromethylsulfonyl)methylidene group was synthesized. Thermal transylidation of 4-(trifluoromethyl)phenylbromonium his (trifluoromethylsulfonyl)methylide in chlorobenzene as a solvent at 130 degrees C afforded phenylchloronium bis(trifluoromethylsulfonyl)methylide in a moderate yield. Phenylbromonium and phenyliodonium ylides were also prepared by the thermal transylidation to bromo- and iodobenzenes. The reaction probably involves initial thermal generation of bissulfonylcarbene (Tf2C:), followed by nucleophilic attack of a halobenzene toward the electron-deficient carbene center. Solid-state structures of these aliphatic phenylhalonium ylides were lanalyzed and compared with each other. (C) 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:325-330, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20683

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Weakly nucleophilic conjugate bases of superacids as powerful nucleophiles in vinylic bimolecular nucleophilic substitutions of simple β- alkylvinyl(aryl)-λ3-bromanes

Ochiai M., Okubo T., Miyamoto K.

Journal of the American Chemical Society 133 ( 10 ) 3342 - 3344 2011.03

ISSN 00027863

We report herein, for the first time, the stereoselective synthesis of simple (E)-β-alkylvinyl(aryl)-λ3-bromanes via a boron-λ3-bromane exchange reaction and their unique bimolecular nucleophilic substitutions at the vinylic ipso carbon atom under mild conditions. Interestingly, even weakly nucleophilic anions such as conjugate bases of superacids (HBF4, TfOH, Tf2CH 2, Tf3CH, Tf2NH, etc.) function as nucleophiles toward the vinyl-λ3-bromanes. For instance, the vinylic SN2 reaction of (E)-vinyl-λ3-bromanes with potassium bis(triflyl)methanide stereoselectively produced (Z)-vinyloxy oxosulfonium ylides with exclusive inversion of configuration via oxygen attack, while that with potassium bis(triflyl)imide afforded predominantly (Z)-vinyloxysulfoximines. In marked contrast, (E)-β-alkylvinyl- λ3-iodanes do not undergo the vinylic SN2 reaction with these conjugate bases of superacids. The differences between the nucleofugalities of aryl-λ3-iodanyl and aryl- λ3-bromanyl groups (the latter being greater) probably play a pivotal role in these unique reactions. © 2011 American Chemical Society.

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Hypervalent phenyl-λ3-iodane-mediated para-selective aromatic fluorination of 3-phenylpropyl ethers

Saito M., Miyamoto K., Ochiai M.

Chemical Communications 47 ( 12 ) 3410 - 3412 2011.03

ISSN 13597345

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Effects of epalrestat, an aldose reductase inhibitor, on diabetic peripheral neuropathy in patients with type 2 diabetes, in relation to suppression of Nε-carboxymethyl lysine

Kawai T., Takei I., Tokui M., Funae O., Miyamoto K., Tabata M., Hirata T., Saruta T., Shimada A., Itoh H.

Journal of Diabetes and its Complications 24 ( 6 ) 424 - 432 2010.11

ISSN 10568727

Objective: We investigated the efficacy of epalrestat, an aldose reductase inhibitor, for diabetic peripheral neuropathy in Japanese patients with type 2 diabetes. Methods: A total of 38 type 2 diabetic patients (22 men and 16 women; mean±S.E.M. age 63.3±1.0 years; duration of diabetes 9.6±0.8 years) with diabetic neuropathy were newly administered 150 mg/day epalrestat (EP group). Motor nerve conduction velocity (MCV), sensory nerve conduction velocity (SCV), and minimum F-wave latency were evaluated before administration of epalrestat and after 1 and 2 years. Serum N ε-carboxymethyl lysine (CML) as a parameter of advanced glycation end products (AGEs), lipid peroxide, and soluble vascular cell adhesion molecule (sVCAM)-1 as a parameter of angiopathy were measured before administration and after 1 year. We compared the results with those of 36 duration of diabetes-matched type 2 diabetic patients (mean±S.E.M. duration of diabetes 8.2±0.7 years) as control (C group). Results: The EP group showed significant suppression of deterioration of MCV (P<.01) and minimum F-wave latency (P<.01) in the tibial nerve and SCV (P<.05) in the sural nerve compared to those in the C group after 2 years. There was a significant difference in change in CML level between groups (-0.18±0.13 mU/ml in the EP group vs. +0.22±0.09 mU/ml in the C group, P<.05) after 1 year. Conclusions: Epalrestat suppressed the deterioration of diabetic peripheral neuropathy, especially in the lower extremity. Its effects might be mediated by improvement of the polyol pathway and suppression of production of AGEs. © 2010 Elsevier Inc. All rights reserved.

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Imination of sulfides and sulfoxides with sulfonylimino- λ3-bromane under mild, metal-free conditions

Ochiai M., Naito M., Miyamoto K., Hayashi S., Nakanishi W.

Chemistry - A European Journal 16 ( 29 ) 8713 - 8718 2010.08

ISSN 09476539

Exposure of sulfides and sulfoxides to trifluoromethanesulfonylimino(aryl)- λ3-bromane in dichloromethane at 0°C results in a facile transfer of the sulfonylimino group to sulfur atoms and affords N-triflylsulfilimines and -sulfoximines in high yields under transition-metal-free conditions. Imination of (R)-methyl p-tolyl sulfoxide proceeded with predominant retention of configuration at the stereogenic sulfur center. The Hammett plot afforded ρ values of -0.58 for para-substituted thioanisoles and -0.49 for their equivalent sulfoxides, which suggests a buildup of positive charge on the sulfur atoms of sulfides and sulfoxides in the transition state. Calculations suggest a bimolecular nucleophilic-substitution mechanism on the negatively charged nitrogen atom of the sulfonylimino- λ3-bromane, which involves the attack of a sulfide from the opposite side to bromine(III). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Effects of stereochemistry and beta-substituents on the rates of vinylic S(N)2 reaction of hypervalent vinyl(phenyl)-lambda(3)-iodanes with tetrabutylammonium halides

Miyamoto, Kazunori, Okubo, Takuji, Hirobe, Masaya, Kunishima, Munetaka, Ochiai, Masahito

Tetrahedron 66 ( 31 ) 5819 - 5826 2010.07

Accepted, ISSN 00404020

Both stereoisomers of β-(2-phenylethoxy)vinyl-λ3- iodane and (Z)-β-aroyloxyvinyl-λ3-iodane were prepared stereoselectively. These substituted vinyl-λ3-iodanes undergo nucleophilic vinylic substitutions with n-Bu4NX (X=Cl, Br, I) under mild conditions, yielding vinyl halides. The observed inversion of configuration at the ipso vinylic carbon atom is compatible with a concerted vinylic S N2 mechanism. Kinetic measurements indicated that the rates for vinylic SN2 reaction of (Z)-vinyl-λ3-iodane are greater than those of the E-isomer, probably because of the higher ground state energy of the Z-isomer. Electronic effects of β-substituents of vinyl-λ3-iodanes in the vinylic SN2 reaction are also discussed. © 2010 Elsevier Ltd.

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Hypervalent λ3-bromane strategy for Baeyer-Villiger oxidation: Selective transformation of primary aliphatic and aromatic aldehydes to formates, which is missing in the classical Baeyer-Villiger oxidation

Ochiai M., Yoshimura A., Miyamoto K., Hayashi S., Nakanishi W.

Journal of the American Chemical Society 132 ( 27 ) 9236 - 9239 2010.07

ISSN 00027863

A conceptually distinct, modern strategy for Baeyer-Villiger oxidation (BVO) was developed. Our novel method involves initial hydration of water to carbonyl compounds, followed by ligand exchange of hypervalent aryl-λ3-bromane on bromane(III) with the resulting hydrate, yielding a new type of activated Criegee intermediate. The intermediate undergoes BV rearrangement and produces an ester via facile reductive elimination of an aryl-λ3-bromanyl group, because of the hypernucleofugality. The novel strategy makes it possible to induce selectively the BV rearrangement of straight chain primary aliphatic as well as aromatic aldehydes, which is missing in the classical BVO: for instance, octanal and benzaldehyde afforded rearranged formate esters with high selectivity (>95%) under our conditions, while the attempted classical BVO produced only carboxylic acids. This firmly establishes the powerful nature of new methodology for BVO. © 2010 American Chemical Society.

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Organocatalytic Oxidative Cleavage of Carbon-Carbon Double Bonds

Miyamoto Kazunori, Ochiai Masahito

Journal of Synthetic Organic Chemistry, Japan (The Society of Synthetic Organic Chemistry, Japan) 68 ( 3 ) 228 - 237 2010.03

ISSN 00379980

Oxidative cleavage of carbon–carbon double bonds to carbonyl compounds is an essential operation in organic synthesis. Ozonolysis is generally accepted as the standard method for this direct transformation. However, its utility is often limited by safety concerns. Use of high–valent oxometals such as RuO4, OsO4, and MeReO3 in combination with a number of oxygen donors as stoichiometric oxidants is suitable for the oxidative catalytic cleavage of olefins, but they are expensive and/or toxic. Therefore, the development of a safe and environmentally friendly procedure for the cleavage of carbon–carbon double bonds is highly desirable. In this review, we report a safe, environment–friendly, and heavy metal–free ozonolysis of olefins, which involves activated iodosylbenzene monomers, hydroxy–λ3–iodanes, as active species. Organocatalytic version of the oxidative cleavage of olefins that involves in situ generation of hypervalent aryl–λ3–iodanes as effective organocatalysts and the use of m–chloroperbenzoic acid as a stoichiometric terminal oxidant under metal–free conditions is described. Cyclic and acyclic olefins as well as aliphatic and aromatic alkynes were cleaved to carboxylic acids under the organocatalytic conditions.

Hypervalent N-sulfonylimino-λ3-bromane: Active nitrenoid species at ambient temperature under metal-free conditions

Ochiai M., Miyamoto K., Hayashi S., Nakanishi W.

Chemical Communications 46 ( 4 ) 511 - 521 2010

ISSN 13597345

The synthesis and reactions of N-triflylimino-λ3-bromane are summarized. The hypervalent iminobromane functions as a highly active nitrenoid species at ambient temperature under transition metal-free conditions, probably because of the increased hypernucleofugality of aryl- λ3-bromanyl groups compared to that of aryl- λ3-iodanyl groups. The imino-λ3-bromane undergoes stereospecific aziridination of olefins and transylidation to aromatic nitrogen heterocycles, trialkylamines and iodobenzenes. Difluoro- λ3-bromane-induced Hofmann rearrangement of primary arylsulfonamides is also discussed. © 2010 The Royal Society of Chemistry.

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Facile generation of a strained cyclic vinyl cation by thermal solvolysis of cyclopent-1-enyl-λ3-bromanes

Miyamoto K., Shiro M., Ochiai M.

Angewandte Chemie - International Edition 48 ( 47 ) 8931 - 8934 2009.11

ISSN 14337851

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Oxidation of benzyl alcohols with difluoro(aryl)-λ3-bromane: formation of benzyl fluoromethyl ethers via oxidative rearrangement

Ochiai M., Yoshimura A., Miyamoto K.

Tetrahedron Letters 50 ( 33 ) 4792 - 4795 2009.08

ISSN 00404039

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Difluoro-λ3-bromane-induced hofmann rearrangement of sulfonamides: Synthesis of sulfamoyl fluorides

Ochiai M., Okada T., Tada N., Yoshimura A., Miyamoto K., Shiro M.

Journal of the American Chemical Society 131 ( 24 ) 8392 - 8393 2009.06

ISSN 00027863

(Chemical Equation Presented) We report the first example of Hofmann rearrangement of primary arenesulfonamides, which relies on the use of p-trifluoromethylphenyl(difluoro)-λ3-bromane and affords N-arylsulfamoyl fluorides selectively at room temperature. Reaction of aryl-λ3-iodanes with p-toluenesulfonamide affords sulfonylimono-λ3-iodanes, being excellent progenitors for generation of metal-nitrenoid species. In marked contrast, reaction of the difluoro-λ3-bromane with p-toluenesulfonamide in benzene produced unique N-p-tolylsulfamoyl fluoride in a high yield, through Hofmann rearrangement. Arenesulfonamides with electron-donating (p-MeO and o-Me) and -withdrawing substituents (p-F, p-Cl, and p-CF3) efficiently undergoes the λ3-bromane-induced Hofmann rearrangement. The structure of N-p-tolylsulfamoyl fluoride was determined by a single-crystal X-ray analysis. The differences in nucleofugality between aryl- λ3-iodanyl and aryl-λ3-bromanyl groups, the later being greater, probably play a pivotal role in determining the reaction course. The results obtained from the reaction of 2,3,5,6- tetramethylbenzenesulfonamide strongly suggest that generation of sulfonyl nitrene will not be involved in this rearrangement. Copyright © 2009 American Chemical Society.

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Lodomesitylene-catalyzed oxidative cleavage of carbon-carbon double and triple bonds using m-chloroperbenzoic acid as a terminal oxidant

Miyamoto K., Sei Y., Yamaguchi K., Ochiai M.

Journal of the American Chemical Society 131 ( 4 ) 1382 - 1383 2009.02

ISSN 00027863

Transition metal-catalyzed oxidative cleavage of carbon-carbon multiple bonds has emerged as a powerful tool in organic synthesis. High-valent oxometals, mostly of Ru, Os, Mn, Mo, W, and Re, were used catalytically as reactive oxygen transfer agents to the multiple bonds. Reported here for the first time are the organocatalytic versions of the oxidative cleavage reactions. Our method involves use of iodomesitylene as an effective organocatalyst, which generates an active aryl(hydroxy)-B3-iodane 5 in situ, and m-chloroperbenzoic acid (m-CPBA) as a terminal oxidant under metal-free conditions. Cyclic and acyclic olefins as well as aliphatic and aromatic alkynes were smoothly cleaved to carboxylic acids under the organocatalytic conditions. Copyright © 2009 American Chemical Society.

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