Browsing by Author "Ryu, Ilhyong"

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A Palladium/Light System Combined with Hanztsch Ester: Radical Vinylation of Alkyl Iodides with Vinyl Bromides
(2017-04-01)
Sumino, Shuhei
;
Ryu, Ilhyong
;
應用化學系
;
Department of Applied Chemistry
Radical vinylation of alkyl iodides with vinyl bromides proceeds smoothly with a combined Pd/light/Hanztschester system. In this reaction system, the Hanztsch ester acts as an effective reducing reagent of Pd-II to Pd-0 that generates key alkyl radicals via single electron transfer (SET) with alkyl iodides upon photo-excitation.
A Theoretical Study on Radical-based Aminocarbonylation of Aryl Iodides
(2018-09-01)
Kawamoto, Takuji
;
Matsubara, Hiroshi
;
Fukuyama, Takahide
;
Ryu, Ilhyong
;
應用化學系
Aminocarbonylation of aromatic iodides with CO and amines gives aromatic amides under photoirradiation conditions. DFT calculations predict that methylamine adds to benzoyl radical to give a zwitterionic radical, which would afford the product via two pathways: (a) an amine-assisted proton transfer followed by a single electron transfer reaction (SET) with iodobenzene or (b) complexation with iodobenzene and then the SET.
Alkenylation and Allylation Reactions of Alkyl Halides Using Photo Catalyst
(2019-05-01)
Sumino, Shuhei
;
Ryu, Ilhyong
;
應用化學系
;
Department of Applied Chemistry
Radical addition/beta-fragmentation sequence has long been utilized for alkenylation and allylation of alkyl halides, in which key alkyl radicals are generated from alkyl halides by S(H)2 reaction typically using tributyltin radical. In this article, we describe modernized alkenylation and allylation of alkyl halides, in which alkyl radical generation is carried out by electron transfer under photoirradiation with the use of transition metal catalyst, which enables us to carry out the radical alkenylation and allylation without the use of radical initiators nor chain transfer reagents. Indeed, radical alkenylation of alkyl iodides using alkenyl bromides proceeded well by the use of a Pd/light combined system involving Hantzsch ester. Alkenyl and allyl sulfones worked better, since the system can obviate the use of Hantzsch ester. Mechanistically spontaneous reductive elimination of PhSO2I is suggested to recover the Pd catalyst. We also discuss allylation of gem-difluoromethylene-containing alkyl halides using allyl sulfones, which is best performed by the use of a visible light photoredox system based on Ru-catalyst.
Ammonium chiral borate salt catalyzed asymmetric Friedel-Crafts alkylation of indoles with alpha,beta-disubstituted enals
(2017-08-15)
Ueda, Mitsuhiro
;
Yagyu, Yoshitaka
;
Ryu, Ilhyong
;
應用化學系
;
Department of Applied Chemistry
In, the presence of a catalytic amount of ammonium chiral borate salt, asymmetric Friedel-Crafts alkylation of indoles with alpha,beta-disubstituted enals proceeded to give the corresponding 1,4-addition products with moderate enantioselectivities. (C) 2017 Elsevier Ltd. All rights reserved.
Applications of Radical Carbonylation and Amine Addition Chemistry: 1,4-Hydrogen Transfer of 1-Hydroxylallyl Radicals
(2018-09-01)
Matsubara, Hiroshi
;
Kawamoto, Takuji
;
Fukuyama, Takahide
;
Ryu, Ilhyong
;
應用化學系
CONSPECTUS: 1,4-Hydrogen transfer from the 1-hydroxyallyl radical to give the enoxyl (alpha-keto) radical is an exothermic process with a high activation energy based on DFT calculations. The lack of experimental examples of such 1,4-H shift reactions lies in the difficulty of generating the 1-hydroxyallyl radical. We have shown that radical carbonylation of alkenyl radicals with CO followed by nucleophilic trapping of the carbonyl portion of the resulting radical by amines gives rise to 1-amino-substituted 1-hydroxyallyl radicals in situ. At the outset of this chemistry, we examined intramolecular trapping reactions via radical carbonylation of alkynylamines mediated by tributyltin hydride. Consequently, alpha-methylene lactams were obtained, for which the initially formed 1-amino-substituted 1-hydroxyallyl radical underwent a 1,4-H shift followed by subsequent beta-scission, which led to the expulsion of a tributyltin radical. A competing pathway of the 1,4-H shift of 1-amino-substituted 1-hydroxyallyl radicals involving hydrogen abstraction was observed, which led to the formation of alpha-stannylmethylene lactams as a major byproduct. However, in contrast, when intermolecular trapping of alpha-ketenyl radicals by amines was carried out, the 1,4-H shift from the 1-amino-substituted 1-hydroxyallyl radical became the major pathway, which gave good yields of alpha,beta-unsaturated amides. Thus, we were able to develop three-component reactions comprising terminal alkynes, CO, and amines that led to alpha,beta-unsaturated amides via the 1,4-H shift reaction. DFT calculations support the observation that the 1,4-H shift is more facile when 1-hydroxyallyl radicals have both 1-amino and 3-tin substituents. The choice of substituents on the amine nitrogen is also important, since N-C bond cleavage via an S(H)2-type reaction can become a competing pathway. Such an unusual S(H)2-type reaction at the amine nitrogen is favored when the leaving alkyl radicals are stable, such as PhC(center dot)H(CH3) and t-Bu center dot. Interestingly, even nucleophilic attack of tertiary amines onto alpha-ketenyl radicals causes cleavage of the CN bond. For this reaction, DFT calculations predict an indirect homolytic substitution mechanism involving expulsion of alkyl radicals through the zwitterionic radical intermediate arising from nucleophilic amine addition onto the alpha-ketenyl radical. In contrast, the carbonylation of aryl radicals, generated from aryl iodides, in the presence of amines gave aromatic carboxylic amides in good yields. It is proposed that radical anions originating from acyl radicals and amines undergo electron transfer to aryl iodides to give aminocarbonylation products.
Bromine-Radical-Mediated Site-Selective Allylation of C(sp(3))-H Bonds
(2019-03-01)
Ueda, Mitsuhiro
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Maeda, Ayami
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Hamaoka, Kanako
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Sasano, Mika
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Fukuyama, Takahide
The C(sp(3))-H allylation of alkanes is investigated by using allyl bromides under radical reaction conditions. In many cases, methine C-H allylation preceded methylene and methyl C-H allylation with complete or a high degree of site selectivity. The C-H allylation of allylic compounds, such as allylbenzene, gives 1,5-dienes with the S(H)2' reactions of the allyl radicals occurring at the less hindered carbon.
Bromine-Radical-Mediated Synthesis of -Functionalized ,- and ,epsilon-Unsaturated Ketones via C-H Functionalization of Aldehydes
(2017-09-01)
Kippo, Takashi
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Kimura, Yuki
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Ueda, Mitsuhiro
;
Fukuyama, Takahide
;
Ryu, Ilhyong
The bromine-radical-mediated allylation reaction of aldehydes was studied. In the presence of V-65 as radical initiator, the reaction of aldehydes with allyl bromides gave beta,gamma-unsaturated ketones in good yields (13 examples, 45-84%). The reaction is triggered by hydrogen abstraction from the aldehyde by bromine radical to form an acyl radical, which undergoes an S(H)2'-type addition-elimination reaction with allyl bromides to give coupling products with liberation of bromine radical. Three-component coupling reactions comprising aldehydes, electron-deficient alkenes, and methallyl bromide also proceeded to give delta,epsilon-unsaturated ketones.
Bromoallylation of Alkenes Leading to 4-Alkenyl Bromides Based on Trapping of beta-Bromoalkyl Radicals
(2017-10-06)
Kippo, Takashi
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Hamaoka, Kanako
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Ueda, Mitsuhiro
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Fukuyama, Takahide
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Ryu, Ilhyong
A radical-chain addition of allyl bromides to aryl alkenes, vinyl ester, and vinyl phthalimide was studied in which elusive beta-bromodkyl radicals were trapped efficiently to give 5-bromo-1-pentenes in good to high yields (16 examples). A subsequent carbonylative radical cyclization with AIBN/Bu3SnH/CO was successful in giving the corresponding 3,5-disubstituted cyclohexanone derivatives in moderate yields. Synthesis of a piperidine ring was also successful by subsequent reaction with primary amine.
Carbonylation of Alkyl Radicals Derived from Organosilicates through Visible-Light Photoredox Catalysis
(2019-02-04)
Cartier, Alex
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Levernier, Etienne
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Corce, Vincent
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Fukuyama, Takahide
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Dhimane, Anne-Lise
Primary, secondary, and tertiary alkyl radicals formed by the photocatalyzed oxidation of organosilicates underwent efficient carbonylation with carbon monoxide (CO) to give a variety of unsymmetrical ketones. This study introduces the possibility of radical carbonylation under a photooxidative regime.
Cobalt-catalyzed regioselective [3+2] annulation of ortho-formyl and acetyl substituted phenylboronic acids with alkynes
(2017-07-26)
Ueda, Mitsuhiro
;
Ueno, Tamami
;
Suyama, Yuki
;
Ryu, Ilhyong
;
應用化學系
Treatment of alkynes with ortho-formyl and acetyl phenylboronic acids in the presence of a cobalt catalyst resulted in the formation of 2,3-disubstituted indenols in good yields. When aryl silyl alkynes were used, 2-aryl-3-silyl indenols were obtained regioselectively in good yields. (C) 2017 Elsevier Ltd. All rights reserved.
Cooperative Polar/Steric Strategy in Achieving Site-Selective Photocatalyzed C(sp(3))-H Functionalization
(2017-06-27)
Yamada, Keiichi
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Fukuyama, Takahide
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Fujii, Saki
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Ravelli, Davide
;
Fagnoni, Maurizio
Synergistic control over the S(H)2 transition states of hydrogen abstraction exploiting polar and steric effects provides a promising cooperative strategy for site-selective C(sp(3))-H functionalization using decatungstate anion photocatalysis. By using this photocatalytic approach, the C-H bonds of substituted lactones and cyclic ketones were functionalized selectively. In the remarkable case of 2-isoamyl 4-tert-butyl cyclohexanone (1t) bearing five methyl, five methylene, and three methine C-H bonds, one methine C-H bond in the isoamyl tether was selectively functionalized.
Efficient Flow Fischer Esterification of Carboxylic Acids with Alcohols Using Sulfonic Acid-Functionalized Silica as Supported Catalyst
(2017-05-01)
Furuta, Akihiro
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Fukuyama, Takahide
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Ryu, Ilhyong
;
應用化學系
;
Department of Applied Chemistry
Flow Fischer esterification of carboxylic acids using hydroxy-substituted sulfonic acid-functionalized silica (HO-SAS) packed into a stainless steel column reactor was investigated. HO-SAS well catalyzed flow esterification of long chain carboxylic acids with methanol within 3 min of residence time at 110 C-omicron, and the methyl esters were quantitatively obtained. The flow esterification protocol was applied to the synthesis of a variety of esters (19 examples) and scalable synthesis was also successful.
Electron transfer-induced reduction of organic halides with amines
(2018-06-04)
Fukuyama, Takahide
;
Fujita, Yuki
;
Miyoshi, Hayato
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Ryu, Ilhyong
;
Kao, Shih-Chieh
Reduction of a variety of organo halides was examined by using amines as a sacrificial hydrogen source. UV light-induced reduction of vinyl and aryl halides with triethylamine proceeded smoothly to give the corresponding reduced products. High temperature heating also caused the reduction and DABCO (1,4-diazabicyclo[2.2.2]octane) also served as a good reducing reagent.
Electron-Transfer-Induced Intramolecular Heck Carbonylation Reactions Leading to Benzolactones and Benzolactams
(2018-08-01)
Fukuyama, Takahide
;
Bando, Takanobu
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Ryu, Ilhyong
;
應用化學系
;
Department of Applied Chemistry
A metal-catalyst-free intramolecular Heck carbonylation reaction of benzyl alcohols and benzyl amines with carbon monoxide under heating at 250 degrees C affords the corresponding benzolactones and benzolactams in good to excellent yields. A hybrid radical/ionic chain mechanism, involving electron transfer from radical anions generated by nucleophilic attack of alcohols or amines on intermediate acyl radicals, is proposed.
Flow Dehydration and Hydrogenation of Allylic Alcohols: Application to the Waste-Free Synthesis of Pristane
(2017-03-10)
Furuta, Akihiro
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Hirobe, Yuki
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Fukuyama, Takahide
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Ryu, Ilhyong
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Manabe, Yoshiyuki
Hydroxy-substituted sulfonic acid functionalized silica (HO-SAS) in combination with THF containing a small amount of water as a solvent proved to be a reliable system for the dehydration of allylic alcohols. This process generally caused dehydration within 1 min through a column reactor charged with HO-SAS. The flow dehydration was sequenced by flow hydrogenation, which resulted in the synthesis of pristane. A scalable flow synthesis of pristane was successfully performed and afforded 10 g of pristane after an operation of 2 h. We also performed dehydration and hydrogenation by using a mixed column of HO-SAS and 10 % Pd/C.
Ionic liquids are not innocent in Pd catalysis. C-H arylation of thiazolium and imidazolium ionic liquids with aryl halides
(2017-09-01)
Fukuyama, Takahide
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Rahman, Md Taifur
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Mashima, Hiroshi
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Takahashi, Hideo
;
Ryu, Ilhyong
The ionic liquids bearing an aromatic vinylic C-H moiety are not innocent during Pd-catalyzed crosscoupling reactions of aryl halides, since palladium-catalyzed direct C-H arylation of thiazolium and imidazolium ionic liquids competes.
Palladium/Light Induced Radical Alkenylation and Allylation of Alkyl Iodides Using Alkenyl and Allylic Sulfones
(2018-02-16)
Sumino, Shuhei
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Uno, Misae
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Huang, Hsin-Ju
;
Wu, Yen-Ku
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Ryu, Ilhyong
Alkenylation and allylation of alkyl iodides with alkenyl and allyl sulfones, respectively, took place under Pd/photoirradiation system. The initial alkyl radical, derived from a single electron transfer between Pd(0) and RI, underwent the title transformations. Pd(0) was regenerated through a reductive elimination of PhSO2PdI, which is formed by the combination of the sulfonyl radical and the palladium radical. The addition of water was effective, presumably by pushing the equilibrium through hydrolysis of PhSO2I.
Pd/light-induced alkyl-alkenyl coupling reaction between unactivated alkyl iodides and alkenylboronic acids
(2020-05-21)
Huang, Hsin-Ju
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Wang, Yi-Ting
;
Wu, Yen-Ku
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Ryu, Ilhyong
;
應用化學系
Alkyl-alkenyl coupling reaction between unactivated alkyl iodides and 2-arylalkenylboronic acids utilizing a Pd/light combined system was studied. This reaction provided 2-alkylarylalkenes in good yields. It is proposed that in this reaction alkyl radicals are formed by SET from a Pd catalyst to alkyl iodides, which then undergo addition reactions to form C-C double bonds of alkenyl boronic acids and the subsequent beta-fragmentation of boronyl radicals leads to the formation of alkyl-substituted arylalkenes.
Photocatalyzed Site-Selective C(sp(3))-H Functionalization of Alkylpyridines at Non-Benzylic Positions
(2017-12-01)
Fukuyama, Takahide
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Nishikawa, Tomohiro
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Yamada, Keiichi
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Ravelli, Davide
;
Fagnoni, Maurizio
Tetrabutylammonium decatungstate (TBADT)-photocatalyzed C-H functionalization of alkylpyridines was investigated. Unlike alkylbenzene counterparts, alkylation of alpha-C-H bonds did not proceed for the reaction of 2- and 4-alkylpyridines and reluctantly proceeded for 3-alkylpyridines, which allow site-selective C(sp(3))-H functionalization at nonbenzylic positions. The observed nonbenzylic site selectivities are rationalized by the polar inductive effects of pyridyl groups in the S-H(2) transition states. Consecutive gamma-functionalization and alpha-bromofunctionalization were successfully carried out in selected cases.
Photoredox-Catalyzed Hydrodifluoroalkylation of Alkenes Using Difluorohaloalkyl Compounds and a Hantzsch Ester
(2017-05-19)
Sumino, Shuhei
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Uno, Misae
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Fukuyarna, Takahide
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Ryu, Ilhyong
;
Matsuura, Makoto
Photoredox-catalyzed hydrodifluoroalkylation of alkenes proceeded smoothly in the presence of a Hantzsch ester as a hydrogen source under visible light irradiation. The reaction was also applicable to the hydrodifluoroalkylation of alkynes, and a continuous photo flow reaction was also successful.