title: Synthesis of new chiral 2,2'-bipyridine ligands and their application in copper-catalyzed asymmetric allylic oxidation and cyclopropanation.
abstract: 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, beta-pinene (10 --> 1), 3-carene (14 --> 3 and 5), 2-carene (28 --> 4), alpha-pinene (43 --> 6-8), and dehydropregnenolone acetate (48 --> 9), respectively. Copper(I) complexes, derived from these ligands and (TfO)(2)Cu (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 < or =76% enantioselectivity and approximately 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.
authors.affiliation: Department of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Malkov
authors.forename: Daniele
authors.initials: D
authors.lastname: Pernazza
authors.forename: Mark
authors.initials: M
authors.lastname: Bell
authors.forename: Marco
authors.initials: M
authors.lastname: Bella
authors.forename: Antonio
authors.initials: A
authors.lastname: Massa
authors.forename: Filip
authors.initials: F
authors.lastname: Teplý
authors.forename: Premji
authors.initials: P
authors.lastname: Meghani
authors.forename: Pavel
authors.initials: P
authors.lastname: Kocovský