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Synthesis of 3,3-Disubstituted Oxindoles by Palladium-Catalyzed Asymmetric Intramolecular α-Arylation of Amides: Reaction Development and Mechanistic Studies

Authors
Sharma, Akhilesh K.
Sunoj, Raghavan B.
Published in Chemistry - A European Journal. 2013, vol. 19, no. 36, p. 11916-11927
Abstract Palladium complexes incorporating chiral N-heterocyclic carbene (NHC) ligands catalyze the asymmetric intramolecular α-arylation of amides producing 3,3-disubstituted oxindoles. Comprehensive DFT studies have been performed to gain insight into the mechanism of this transformation. Oxidative addition is shown to be rate-determining and reductive elimination to be enantioselectivity-determining. The synthesis of seven new NHC ligands is detailed and their performance is compared. One of them, L8, containing a tBu and a 1-naphthyl group at the stereogenic centre, proved superior and was very efficient in the asymmetric synthesis of fifteen new spiro-oxindoles and three azaspiro-oxindoles often in high yields (up to 99 %) and enantioselectivities (up to 97 % ee; ee=enantiomeric excess). Three palladacycle intermediates resulting from the oxidative addition of [Pd(NHC)] into the aryl halide bond were isolated and structurally characterized (X-ray). Using these intermediates as catalysts showed alkene additives to play an important role in increasing turnover number and frequency.
Keywords ArylationAsymmetric catalysisN-heterocyclic carbenesOxindolesPalladium
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Other version: http://doi.wiley.com/10.1002/chem.201301572
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KATAYEV, Dmitry et al. Synthesis of 3,3-Disubstituted Oxindoles by Palladium-Catalyzed Asymmetric Intramolecular α-Arylation of Amides: Reaction Development and Mechanistic Studies. In: Chemistry - A European Journal, 2013, vol. 19, n° 36, p. 11916-11927. https://archive-ouverte.unige.ch/unige:29561

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Deposited on : 2013-09-04

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