Synthesis of 3,3-Disubstituted Oxindoles by Palladium-Catalyzed Asymmetric Intramolecular α-Arylation of Amides: Reaction Development and Mechanistic Studies
| Autor: | Akhilesh K. Sharma, Dmitry Katayev, Raghavan B. Sunoj, E. Peter Kündig, Yi-Xia Jia, Céline Besnard, Dipshikha Banerjee |
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| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
Indoles
Enantioselective Synthesis Stereochemistry Aryl halide Quaternary Carbon Centers Alkenes Ligands Imidazolium Salts Catalysis Reductive elimination Stereocenter Alpha-Arylation Asymmetric catalysis N-heterocyclic carbenes Enantiomeric excess chemistry.chemical_classification Asymmetric Catalysis Molecular Structure Chemistry Alkene 3-Substituted Oxindoles Organic Chemistry Heck Reactions Enantioselective synthesis N-Heterocyclic Carbenes Complexes Synthesis Stereoisomerism General Chemistry Aldol-Type Reaction Heterocyclic Carbene Ligands Arylation Amides Oxidative addition Oxindoles Intramolecular force ddc:540 3-Allyl-3-Aryl Oxindoles Methane Palladium |
| Zdroj: | Chemistry-A European Journal, Vol. 19, No 36 (2013) pp. 11916-11927 |
| ISSN: | 0947-6539 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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