Browsing by Author "Fukuyama, Takahide"

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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.
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
;
Maeda, Ayami
;
Hamaoka, Kanako
;
Sasano, Mika
;
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
;
Kimura, Yuki
;
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
;
Hamaoka, Kanako
;
Ueda, Mitsuhiro
;
Fukuyama, Takahide
;
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
;
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.
Cooperative Polar/Steric Strategy in Achieving Site-Selective Photocatalyzed C(sp(3))-H Functionalization
(2017-06-27)
Yamada, Keiichi
;
Fukuyama, Takahide
;
Fujii, Saki
;
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
;
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
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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
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Bando, Takanobu
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Ryu, Ilhyong
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應用化學系
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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
;
Hirobe, Yuki
;
Fukuyama, Takahide
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Ryu, Ilhyong
;
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
;
Rahman, Md Taifur
;
Mashima, Hiroshi
;
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.
Photocatalyzed Site-Selective C(sp(3))-H Functionalization of Alkylpyridines at Non-Benzylic Positions
(2017-12-01)
Fukuyama, Takahide
;
Nishikawa, Tomohiro
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Yamada, Keiichi
;
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.
Radical Mediated Aza-Pauson-Khand Reaction of Acetylenes, Imines, and CO Leading to Five-Membered Unsaturated Lactams
(2019-10-01)
Fukuyama, Takahide
;
Okada, Takuma
;
Nakashima, Nao
;
Ryu, Ilhyong
;
應用化學系
Formal [2+2+1] cycloaddition reaction involving acetylenes, aromatic imines, and CO was achieved by radical chain reaction, which gave five-membered unsaturated lactams in modest to good yields. When we used 5-chloropentyne, sequential carbonylation took place accompanied with double annulation events to give a cyclohexanone-fused lactam in excellent stereoselectivity.
Scalable Flow Synthesis of [6,6]-Phenyl-C-61-butyric Acid Methyl Ester (PCBM) using a Flow Photoreactor with a Sodium Lamp
(2017-12-01)
Ueda, Mitsuhiro
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Imai, Naoyuki
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Yoshida, Shunsuke
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Yasuda, Hiroshi
;
Fukuyama, Takahide
An efficient flow system was constructed for the synthesis of [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM); the process involved flow [2+1] addition of C-60 and subsequent flow photoisomerization of the resulting fulleroid to PCBM by using a flow photoreactor in combination with an Na lamp. With the present flow system, a scalable synthesis of PCBM (0.79 g/3.3 h) was achieved by continuous operation for 3.3 h.
Site-Selective C(sp(3))-H Functionalization of Fluorinated Alkanes Driven by Polar Effects Using a Tungstate Photocatalyst
(1970-01-01)
Fukuyama, Takahide
;
Nishikawa, Tomohiro
;
Ryu, Ilhyong
;
應用化學系
;
Department of Applied Chemistry
The TBADT-catalyzed C(sp(3))-H functionalization of perfluorophenyl- and perfluoroalkyl-substituted alkanes was studied to determine how the fluorous substituents affect site-selectivity. Alkylation of alkyl-substituted perfluorobenzene avoids alpha-C-H bonds, unlike their alkylbenzene counterparts, allowing site-selective functionalization of C-H bonds remote to the aromatic ring. Alkylation of alkanes having a perfluoroalkyl group also avoided alpha-C-H bonds. Radical polar effects in the S(H)2 transition states could explain this avoidance of alpha-C-H functionalization.
Site-Selective C-H Functionalization by Decatungstate Anion Photocatalysis: Synergistic Control by Polar and Steric Effects Expands the Reaction Scope
(2018-01-01)
Ravelli, Davide
;
Fagnoni, Maurizio
;
Fukuyama, Takahide
;
Nishikawa, Tomohiro
;
Ryu, Ilhyong
The synergistic control of the S(H)2 transition states of hydrogen abstraction by polar and steric effects provides a promising strategy in achieving site-selective C(sp(3))-H functionalization under decatungstate anion photo catalysis. By using this photocatalytic approach, the C-H bonds of alkanes, alcohols, ethers, ketones, amides, esters, nitriles, and pyridylalkanes were functionalized site-selectively. In the remarkable case of a 2,4-disubstituted cyclohexanone bearing five methyl, five methylene, and three methine C-H bonds, one methine C-H bond in the isoamyl tether was selectively functionalized.
Site-selectivity in TBADT-photocatalyzed C(sp(3))-H Functionalization of Saturated Alcohols and Alkanes
(2018-01-01)
Fukuyama, Takahide
;
Yamada, Keiichi
;
Nishikawa, Tomohiro
;
Ravelli, Davide
;
Fagnoni, Maurizio
Site-selectivity in C(sp(3))-H functionalization of aliphatic alcohols and alkanes was studied using the decatungstate anion as a photocatalyst. In the case of aliphatic alcohols, C-H bond alpha to the hydroxy group was preferentially functionalized. The alpha-site-selectivity is rationalized by polar effects imparted by the hydroxy group in the S(H)2 transition states. In contrast, C-H functionalization of alkanes was largely affected by steric effects.
Synthesis of 4,4-Difluoroalkenes by Coupling of alpha-Substituted alpha,alpha-Difluoromethyl Halides with Allyl Sulfones under Photoredox Catalyzed Conditions
(2019-07-19)
Uno, Misae
;
Sumino, Shuhei
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Fukuyama, Takahide
;
Matsuura, Makoto
;
Kuroki, Yoshichika
Photoredox-catalyzed allylation of alpha-gem-difluorinated organohalides with allyl sulfones proceeded smoothly under visible light irradiation to give 4,4-difluoroalkenes in good yields. In the presence of catalytic Ru(bpy)(3)Cl-2, Hantzsch ester, and diisopropylethylamine, the reaction was complete within 2 h. Using the same methodology, three-component cascade reactions to give 6,6-difluoroalkenes were carried out successfully.
Synthesis of Aliphatic Amides through a Photoredox Catalyzed Radical Carbonylation Involving Organosilicates as Alkyl Radical Precursors
(1970-01-01)
Cartier, Alex
;
Levernier, Etienne
;
Dhimane, Anne-Lise
;
Fukuyama, Takahide
;
Ollivier, Cyril
Alkyl radicals, from primary to tertiary, formed by photocatalyzed oxidation of organosilicates, are involved efficiently in radical carbonylation with carbon monoxide (CO), in the presence of various amines and CCl4, leading to a variety of amides in moderate to good yields.