2021
DOI: 10.1002/adsc.202100234
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Rapid Oxidation Indoles into 2‐Oxindoles Mediated by PIFA in Combination with n‐Bu4NCl ⋅ H2O

Abstract: We report the development of a rapid approach for directly converting indoles into 2-oxindoles promoted by HOCl formed in situ from the combination of (bis(trifluoroacetoxy) iodo)benzene (PIFA) and n-Bu 4 NCl • H 2 O. The procedure is widely functional group tolerant and provides 2-oxindoles in up to 95% yield within 5 min. The potential applications of the developed methodology are demonstrated by the gram-scale preparation of 3-methyl-2-oxindole (11 a), the one-pot two-step syntheses of spiro-oxindoles 26 a … Show more

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Cited by 16 publications
(9 citation statements)
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“…Finally, inspired by recent discoveries regarding the oxidation chemistry of indole heterocycles by heme-enzymes and in view to replace the highly acidic and oxidizing reagents (HCl, hypervalent halides, peroxy acids, oxone) typically employed with state-of-the-art methodologies by more sustainable and benign protocols, we applied our iron-catalyzed methodology to indole 1s (Scheme ). Under the developed reaction conditions, full conversion was observed in only 30 min and the 2-oxindole product 2s was isolated in a nonoptimized 71% yield.…”
Section: Resultsmentioning
confidence: 99%
“…Finally, inspired by recent discoveries regarding the oxidation chemistry of indole heterocycles by heme-enzymes and in view to replace the highly acidic and oxidizing reagents (HCl, hypervalent halides, peroxy acids, oxone) typically employed with state-of-the-art methodologies by more sustainable and benign protocols, we applied our iron-catalyzed methodology to indole 1s (Scheme ). Under the developed reaction conditions, full conversion was observed in only 30 min and the 2-oxindole product 2s was isolated in a nonoptimized 71% yield.…”
Section: Resultsmentioning
confidence: 99%
“…In addition, 3-methyl-2-oxindoles are also accessed by various reducing 8 and oxidizing 9 protocols. Recently, a borrowing hydrogen approach has been explored by Morrill et al 10 and Venkatasubbaiah et al 11 to prepare 3-methyl-2-oxindoles using transition metal catalysts with methanol as a methylating agent.…”
Section: Introductionmentioning
confidence: 99%
“…13 C­{ 1 H} NMR (150 MHz, CDCl 3 ) δ 174.9, 141.2, 130.7, 126.4, 126.0, 123.6, 110.8, 52.1. All analytic data match the reported data …”
Section: Methodsmentioning
confidence: 55%