Regioselective synthesis of optically active (pyrazolyl)pyridines with adjacent quaternary carbon stereocenter: chiral N, N-donating ligands

• Published in: Tetrahedron Vol. 61; no. 3; pp. 623 - 628
• Main Authors: Kowalczyk, Rafał, Skarżewski, Jacek
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 17.01.2005; Elsevier
• Subjects: Chemistry; Chemistry, Organic; Cyclization; Nitrogen chiral ligands; Physical Sciences; Pirazolylpyridines; Quaternary carbon stereocenter; Science & Technology; Pirazolylpyridines; Quaternary carbon stereocenter; Cyclization; Nitrogen chiral ligands; ASYMMETRIC CATALYSIS; CONVENIENT SYNTHESIS; COORDINATION CHEMISTRY; PYRAZOLYLPYRIDINE; PYRAZOLES; ACID; ABSOLUTE-CONFIGURATION; COMPLEXES; DERIVATIVES; HETEROCYCLIC LIGANDS
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2004.10.092

Novel optically active 2-(pyrazol-1-yl)pyridines have been prepared using resolved the O-methyl ether of atrolactic acid as a source of the adjacent quaternary carbon stereocenter. Different regioisomers were formed selectively in the reaction of 2-hydrazinopyridines with the chiral 1,3-diketone and in the nucleophilic substitution of 2-chloropyridines with the potassium salt of the chiral pyrazole. The second route gave 2-(pyrazol-1-yl)pyridines with the stereogenic center neighboring the coordinating nitrogen in the pyrazole ring. Also, new C 2-symmetric chiral ligands based on 2,6-bis(pyrazolyl)pyridine and 6,6′-bis(pirazolyl)-2,2′-bipyridine structures were obtained. Graphical Abstract