- Me2AlCl-mediated carboxylation, ethoxycarbonylation, and carbamoylation of indoles
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Various 1-methyl-, 1-triisopropylsilyl-, and 1-benzylindoles are carboxylated under CO2 pressure (3.0 MPa) with the aid of 1.0 molar equiv of Me2AlCl to give 1-substituted indole-3-carboxylic acids in good to excellent yields. Mechanistic studies suggest that the intermediate, an indol-3-ylaluminum ate complex, was reversibly formed by electrophilic addition of Me2AlCl to the substrate followed by deprotonation of the resulting adduct. This method is successfully extended to alkoxycarbonylation with ethyl chloroformate and carbamoylation with naphthalen-1-yl isocyanate, which afford ethyl indole-3-carboxylates and N-naphthalen-1-ylindole-3-carboxamides, respectively.
- Nemoto, Koji,Tanaka, Shinya,Konno, Megumi,Onozawa, Satoru,Chiba, Masafumi,Tanaka, Yuuki,Sasaki, Yosuke,Okubo, Ryo,Hattori, Tetsutaro
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p. 734 - 745
(2016/01/15)
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- Direct carboxylation of simple arenes with CO2 through a rhodium-catalyzed C-H bond activation
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Direct carboxylation of simple arenes under atmospheric pressure of CO2 is achieved through a rhodium-catalyzed C-H bond activation without the assistance of a directing group. Various arenes such as benzene, toluene, xylene, electron-rich or electron-deficient benzene derivatives, and heteroaromatics are directly carboxylated with high TONs. This journal is
- Suga, Takuya,Mizuno, Hajime,Takaya, Jun,Iwasawa, Nobuharu
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supporting information
p. 14360 - 14363
(2015/02/19)
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- Copper-catalyzed methyl esterification reactions via C-C bond cleavage
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The highly effective synthesis of methyl esters from benzylic alcohols, aldehydes, or acids via copper-catalyzed C-C cleavage from tert-butyl hydroperoxide is reported in this paper for the first time. Our protocol is easily accessible and practical, making it a possible supplement for the traditional way.
- Zhu, Yan,Yan, Hong,Lu, Linhua,Liu, Defu,Rong, Guangwei,Mao, Jincheng
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p. 9898 - 9905
(2013/10/22)
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- Iminoxyl radicals and stable products from the one-electron oxidation of 1-methylindole-3-carbaldehyde oximes
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The radical intermediates and the stable products formed on one-electron oxidation of 1-methylindole-3-carbaldehyde oxime 2a were compared with those of 1-methylindole-3-carboxamidine oxime 4a in aqueous solution. The dibromide radical anion generated radiolytically by pulse radiolysis reacted with both 2a and 4a >C=NOH to yield the radical cations [>C=NOH]·+, which exist in prototropic equilibria with the neutral iminoxyl radicals [>C=NO]· (pKa = 3.53 ? 0.03 and 5.01 ± 0.01 at ionic strength 0.05 M, respectively). This was confirmed by the observed primary salt-effect which accelerated the decay of the radical cations but not the iminoxyl radicals. Methylation of the N-hydroxyimino function in both 2a and 4a precluded deprotonation of the corresponding radical cations [>C=NOCH3]·+. At low concentrations of 2a and high dose rates the 2a radicals [>C=NO]· decayed bimolecularly via unstable dimers to the aldehyde >C=O, with higher concentrations and lower dose rates favouring the chain-catalysed isomerisation of the N-hydroxyimino moiety. Radicals from 4a decay bimolecularly to form unstable dimers which degrade to produce an amide, nitrile and carboxylic acid. The observed differences in the oxidation chemistry of 2a and 4a probably reflect the enhanced stabilisation of iminoxyl radicals through α-amino substitution.
- Everett, Steven A.,Naylor, Matthew A.,Stratford, Michael R.L.,Patel, Kantilal B.,Ford, Eleonora,Mortensen, Alan,Ferguson, Amanda C.,Vojnovic, Borivoj,Wardman, Peter
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p. 1989 - 1997
(2007/10/03)
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