Browsing by Author "Ueda, Mitsuhiro"

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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.
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.
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.
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
;
Imai, Naoyuki
;
Yoshida, Shunsuke
;
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.