900816-50-4Relevant academic research and scientific papers
Enantioselective synthesis of tunable chiral pyridine-aminophosphine ligands and their applications in asymmetric hydrogenation
Liu, Youran,Chen, Fei,He, Yan-Mei,Li, Chenghao,Fan, Qing-Hua
, p. 5099 - 5105 (2019/05/29)
A small library of tunable chiral pyridine-aminophosphine ligands were enantioselectively synthesized based on chiral 2-(pyridin-2-yl)-substituted 1,2,3,4-tetrahydroquinoline scaffolds, which were obtained in high yields and with excellent enantioselectivities via ruthenium-catalyzed asymmetric hydrogenation of 2-(pyridin-2-yl)quinolines. The protocol features a wide substrate scope and mild reaction conditions, enabling scalable synthesis. These chiral P,N ligands were successfully applied in the Ir-catalyzed asymmetric hydrogenation of benchmark olefins and challenging seven-membered cyclic imines including benzazepines and benzodiazepines. Excellent enantio- and diastereoselectivity (up to 99% ee and >20:1 dr), and/or unprecedented chemoselectivity were obtained in the asymmetric hydrogenation of 2,4-diaryl-3H-benzo[b]azepines and 2,4-diaryl-3H-benzo[b][1,4]diazepines.
Chelate [2-(iminoethyl)pyridine N-oxide]metal complexes - Synthesis and structural comparison with their chemically related 2-(iminoethyl)pyridine- derived systems
Nienkemper, Katrin,Kotov, Vasily V.,Kehr, Gerald,Erker, Gerhard,Froehlich, Roland
, p. 366 - 379 (2007/10/03)
The N,O-chelate ligands 2-(iminoethyl)pyridine N-oxide (2a) and 2-(iminoethyl)-6-isopropylpyridine N-oxide (2b) were prepared by conventional synthetic routes, the latter involving a variant of the Reissert-Henze reaction. Treatment of 2a with FeCl2 resulted in a deoxygenation reaction of the ligand and formation of the salt (bis{2-(iminoethyl)-pyridine}FeCl] +[FeCl4]- (18a). In contrast, the reaction of 2a with PdCl2 or CoCl2 cleanly furnished the six-membered chelate [κN,O-2(iminoethyl)pyridine N-oxide]MCl2 complexes (19a, M = Pd) or (20a, M = Co), respectively, which were both characterised by X-ray diffraction. Treatment of 2b with [NiBr2 (dme)], followed by crystallisation from THF, gave the complex [κN,O-2b)NiBr2(THF)] (21b), which features a distorted trigonal-bipyramidal coordination geometry of the central metal atom. The reaction of 2a with [NiBr2(dme)] gave the structurally related complex [(κN,O-2a)NiBr2(κO-2a)] (21a). The N,O-chelate Pd complex 19a was shown to be an active catalyst for the Suzuki coupling reaction. The ligand systems 2a,b and their related 2-(iminoethyl)-pyridines 3a,b and a variety of metal complexes of ligands 3 were also prepared and characterised for comparison by X-ray diffraction. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
