304857-41-8Relevant articles and documents
Synthesis of new chiral 2,2′-bipyridine ligands and their application in Copper-catalyzed asymmetric allylic oxidation and cyclopropanation
Malkov, Andrei V.,Pernazza, Daniele,Bell, Mark,Bella, Marco,Massa, Antonio,Teply, Filip,Meghani, Premji,Kocovsky, Pavel
, p. 4727 - 4742 (2003)
A series of modular bipyridine-type ligands 1 and 3-9 has been synthesized via a de novo construction of the pyridine nucleus. The chiral moieties of these ligands originate from the isoprenoid chiral pool, namely, β-pinene (10 → 1), 3-carene (14 → 3 and 5), 2-carene (28 → 4), α-pinene (43 → 6-8), and dehydropregnenolone acetate (48 → 9), respectively. Copper(I) complexes, derived from these ligands and (TfO)2Cu (1 mol%) upon an in situ reduction with phenylhydrazine, exhibit good enantioselectivity (up to 82% ee) and unusually high reaction rate (typicaly 30 min at room temperature) in allylic oxidation of cyclic olefins (52 → 53). Copper-catalyzed cyclopropanation proceeded with ≤76% enantioselectivity and ～3:1 to 99:1 trans/cis-diastereoselectivity (54 → 55 + 56). The level of the asymmetric induction is discussed in terms of the ligand architecture that controls the stereochemical environment of the coordinated metal.
New Lewis-Basic N-Oxides as Chiral Organocatalysts in Asymmetric Allylation of Aldehydes
Malkov, Andrei V.,Bell, Mark,Orsini, Monica,Pernazza, Daniele,Massa, Antonio,Herrmann, Pavel,Meghani, Premji,Kocovsky, Pavel
, p. 9659 - 9668 (2007/10/03)
Allylation of aromatic and heteroaromatic aldehydes 1a-k with allyltrichlorosilane 2 can be catalyzed by the new heterobidentate, terpene-derived bipyridine N-monoxides 4, 6a,b, and 8-11 (≤10 mol %) to afford (S)-(-)-3 with high enantioselectivities (≤99% ee). The stereochemical outcome has been found to be controlled by the axial chirality of the catalyst, which in turn is determined by the central chirality of the annulated terpene units. Solvent effects on the conversion and the level of asymmetric induction have been elucidated, and MeCN has been identified as the optimal solvent for these catalysts.
PINDY: A novel, pinene-derived bipyridine ligand and its application in asymmetric, copper(I)-catalyzed allylic oxidation
Malkov, Andrei V.,Bella, Marco,Langer, Vratislav,Kocovsky, Pavel
, p. 3047 - 3049 (2007/10/03)
(matrix presented) The title bipyridine ligand (+)-6(PINDY), prepared in five steps from (-)-β-pinene, forms a stable complex with CuCl2 (8) that has been characterized by X-ray crystallography to reveal an unusual geometry at Cu. Triflate 9 proved to catalyze asymmetric allylic oxidation (10 → 11; rt, ～30 min, 49-75% ee).
