Browsing by Author "Sumino, Shuhei"

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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.
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.
Palladium/Light Induced Radical Alkenylation and Allylation of Alkyl Iodides Using Alkenyl and Allylic Sulfones
(2018-02-16)
Sumino, Shuhei
;
Uno, Misae
;
Huang, Hsin-Ju
;
Wu, Yen-Ku
;
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.
Photoredox-Catalyzed Hydrodifluoroalkylation of Alkenes Using Difluorohaloalkyl Compounds and a Hantzsch Ester
(2017-05-19)
Sumino, Shuhei
;
Uno, Misae
;
Fukuyarna, Takahide
;
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.
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
;
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.
Vicinal difunctionalization of alkenes by four-component radical cascade reaction of xanthogenates, alkenes, CO, and sulfonyl oxime ethers
(2019-07-31)
Sumino, Shuhei
;
Fukuyama, Takahide
;
Sasano, Mika
;
Ryu, Ilhyong
;
Jacquet, Antoine
Four-component coupling reactions between xanthogenates, alkenes, CO, and sulfonyl oxime ethers were studied. In the presence of hexabutylditin, working as a propagating radical reagent, the chain reaction proceeds, as expected, taking into account reagents polarities, affording the corresponding functionalized alpha-keto oximes. Although yields are modest, this rare one-pot four-component process is easy to carry out and the resulting compounds, bearing multiple functionalities, have the potential for further elaboration.