201045-67-2Relevant academic research and scientific papers
γ- and δ-lactams through palladium-catalyzed intramolecular allylic alkylation: Enantioselective synthesis, NMR investigation, and DFT rationalization
Bantreil, Xavier,Prestat, Guillaume,Moreno, Aitor,Madec, David,Fristrup, Peter,Norrby, Per-Ola,Pregosin, Paul S.,Poli, Giovanni
, p. 2885 - 2896 (2011/04/24)
The Pd-catalyzed intramolecular allylic alkylation of unsaturated amides to give γ- and δ-lactams has been studied in the presence of chiral ligands. Ligand (R)-3,5-tBu-MeOBIPHEP (MeOBIPHEP=6,6'-dimethoxybiphenyl-2,2- diyl)bis(diphenylphosphine)) afforded the best results and allowed the cyclization reactions to take place in up to 94:6 enantiomeric ratio. A model Pd-allyl complex has been prepared and studied through NMR spectroscopic analysis, which provided insight into the processes responsible for the observed enantiomeric ratios. DFT studies were used to characterize the diastereomeric reaction pathways. The calculated energy differences were in good agreement with the experimentally observed enantiomeric ratios. A transient existence: The Pd-catalyzed intramolecular allylic alkylation of unsaturated amides to give γ- and δ-lactams in the presence of (R)-3,5-tBu-MeOBIPHEP takes place in up to 94:6 enantiomeric ratio (e.r.; see scheme). The energies of the diastereomeric transition states are in good agreement with the experimentally observed enantiomeric ratios.
A new palladium-catalyzed intramolecular allylation to pyrrolidin-2- ones
Giambastiani,Pacini,Porcelloni,Poli
, p. 804 - 807 (2007/10/03)
A novel palladium(0)-catalyzed cyclization to 3,4-disubstituted pyrrolidin-2-ones has been developed. The new approach relies upon the concomitant generation of stabilized acetamide enolate anions and of a π- allyl-palladium appendage, properly tethered by a nitrogen atom. Reaction conditions have been optimized for the methoxycarbonyl-stabilized model reaction [(Z)-2 → 3] and then applied to other substrates. A broad range of acetamide anion stabilizers was shown to allow the desired intramolecular C- C bond formation (MeO2C, MeCO, NC, (EtO)2PO, PhSO2). The cyclizations gave exclusively 5-exo-trig ring closure, thereby affording γ-lactams. All the cyclizations gave the corresponding 3,4-disubstituted pyrrolidin-2-ones with total diastereoselection. Complete trans preference was unequivocally demonstrated for the model reaction via a NOESY experiment.
