- Intramolecular radical acylation of 2-methylsulfonylpyrroles
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Primary alkyl radicals generated (AIBN/Bu3SnH) from 1-(2- or 3- haloalkyl)-2-methylsulfonylpyrroles are intercepted by CO (80 atm), and the acyl radicals so produced undergo intramolecular oxidative cyclization at the α-position, giving bicyclic ketones with retention or loss of the sulfonyl moiety. (C) 2000 Elsevier Science Ltd.
- Miranda, Luis D.,Cruz-Almanza, Raymundo,Alvarez-García, Abraham,Muchowski, Joseph M.
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- Methylthiolation for Electron-Rich Heteroarenes with DMSO-TsCl
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DMSO-TsCl has been developed for direct methylthiolation of various electron-rich heteroarenes (more than 40 examples) with high regioselectivity in moderate to excellent yields (up to 96 %). Especially, pyrroles, furans, and thiophenes can be efficiently mono-methylthiolated. This practical method features scalable, metal-free, mild conditions and is compatible with air and moisture. Several applications of methylthiolated products were demonstrated for the first time. Based on controlled experimental results, a plausible mechanism was proposed with two key intermediates involved in the mechanism being detected by HRMS.
- Zhang, Lei-Yang,Wu, Yue-Hua,Wang, Nai-Xing,Gao, Xue-Wang,Yan, Zhan,Xu, Bao-Cai,Liu, Ning,Wang, Bo-Zhou,Xing, Yalan
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supporting information
p. 1446 - 1451
(2021/02/26)
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- Access to indoles via Diels-Alder reactions of 5-methylthio-2-vinylpyrroles with maleimides
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Diels-Alder reactions of 5-methylthio-2-vinyl-1H-pyrroles with maleimides followed by isomerization gave tetrahydroindoles in moderate to good yield. Aromatization using activated MnO2 in refluxing toluene gave the corresponding 2-methylthioindoles in good yields, and demethylthioation using Raney nickel gave the 2-H indoles in excellent yields. The protection of the adducts produced aromatization in improved yield, demonstrating the effectiveness of the methylthio group as a protecting group for pyrroles; however, 5-methylthio-2-vinylpyrrole was shown to perform with slightly less efficiency than 2-vinylpyrrole in Diels-Alder reactions, indicating the protective group was more deactivating than desired. This route toward indoles offers high convergency and conveniently available starting materials that are easily purified. Bis-methylthioated vinylpyrroles were shown to have potential as highly activated Diels-Alder dienes.
- Noland, Wayland E.,Lanzatella, Nicholas P.,Dickson, Rozalin R.,Messner, Mary E.,Nguyen, Huy H.
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p. 795 - 808
(2013/08/23)
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- Oxidative radical cyclization to pyrroles under reducing conditions. Reductive desulfonylation of α-sulfonylpyrroles with tri-n-butyltin hydride
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1-(2-Bromobenzyl)-2-alkanesulfonylpyrroles (1c, 1d) and 1-(4-bromobutyl)-2-methylsulfonylpyrrols (8) undergo oxidative radical cyclization with partial or complete reductive desulfonylation to the pyrrolizidine derivatives 5 and 9 by an AIBN initiated reaction with tri-n-butyltin hydride.These cyclizations are suggested to proceed via a pseudo SRN1 process involving radical addition to the α position of the pyrrole nucleus not bearing the sulfonyl group.Reductive removal of the alkylsulfonyl moiety is proposed to occur in a second process after completion of the oxidative radical cyclization.The site of the radical addition is supported by deuterium labelling studies.Consistent with the timing of the loss of the sulfonyl group is that 2-alkylsulfonylpyrroles 11 are reductively desulfonylated under the same conditions that effect the oxidative radical cyclizations.
- Antonio, Yulia,Cruz, Ma. Elizabeth De La,Galeazzi, Edvige,Guzman, Angel,Bray, Brian L.,et al.
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