816468-33-4Relevant academic research and scientific papers
Palladium-mediated N-arylation of heterocyclic diamines: Insights into the origin of an unusual chemoselectivity
Cabello-Sanchez, Noemi,Jean, Ludovic,Maddaluno, Jacques,Lasne, Marie-Claire,Rouden, Jacques
, p. 2030 - 2039 (2007/10/03)
The chemoselectivity of the palladium-mediated reaction of bromobenzene with various heterocyclic diamines was studied. Whatever the ligand used, 3-aminopyrrolidine underwent arylation of the secondary amine function (> 82%), whereas the more flexible 3-aminoazepinine was arylated on its primary function (>70%). The ratio "arylation of primary amine versus arylation of secondary amine" of 3-aminopiperidine with bromobenzene varied from 90:10 (BINAP, electron-enriched and hindered biphenyls L2 or L3) to 32:68 with the Josiphos-type ligand L10. The same trend was observed when 4-aminopiperidine was used (82:18 with L2 and 17:83 with L10). This selectivity can be tuned by the choice of aryl halide partners having different steric and electronic properties. A cooperative effect of both nitrogens of diamines during the reaction was deduced from competitive experiments. Finally, 13C and 31P NMR experiments, carried out with 3-aminopyrrolidine at room temperature, support a fast coordination of the primary amine to the metal. Indeed, a palladium complex resulting from the unusual displacement of one phosphane group of the intermediate ArPdX(BINAP) by the primary amino group was characterized.
Palladium-mediated arylation of 3-aminopiperidines and 3-aminopyrrolidines
Jean, Ludovic,Rouden, Jacques,Maddaluno, Jacques,Lasne, Marie-Claire
, p. 8893 - 8902 (2007/10/03)
This paper describes the palladium-catalyzed arylation of 1-substituted 3-aminopyrrolidines or piperidines. Palladium(0) (1-2 mol %) in conjunction with "Buchwald's ligand" [2-(dimethylamino)-2′- (dicyclohexylphosphine)biphenyll was shown to be the catalyst of choice for the coupling with aryl bromides or chlorides. When bromobenzene was used, a strong temperature effect was noticed. Whereas no reaction occurred at 100 °C, yields higher than 85% were obtained at 130 °C for each substrate. Such an effect was not observed when diphosphines were used. Whereas Xantphos and, to a lesser extent BINAP, were moderately efficient in the coupling of all diamines, the palladium-mediated arylation in the presence of monophosphines was strongly dependent on the substrate. The results suggest the participation of both nitrogens of the aminoheterocycle in the reactive intermediate. This participation could also account for the highly selective arylation of the endocyclic nitrogen of unsubstituted 3-aminopyrrolidine or piperidine. Optimal conditions were found for the arylation using 2- or 4-substituted electron-poor or enriched aryl halides.
