1459789-91-3Relevant articles and documents
Synthesis of 3,3-disubstituted oxindoles by palladium-catalyzed asymmetric intramolecular α-arylation of amides: Reaction development and mechanistic studies
Katayev, Dmitry,Jia, Yi-Xia,Sharma, Akhilesh K.,Banerjee, Dipshikha,Besnard, Celine,Sunoj, Raghavan B.,Kuendig, E. Peter
, p. 11916 - 11927 (2013/09/23)
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. Copyright
