title: Preparation of new axially chiral bridged 2,2'-bipyridines and pyridyl monooxazolines (pymox). Evaluation in copper(I)-catalyzed enantioselective cyclopropanation.
abstract: This work reports the synthesis of new axially chiral bridged 2,2'-bipyridines 1 and pyridylmonooxazolines (pymox) 2. The potential of these new axially chiral N,N-ligands was evaluated in asymmetric catalytic cyclopropanation of styrene derivatives 22a-c with diazoesters 21a,b. While 2,2'-bipyridines 1a-c afforded the corresponding cyclopropanes 23a-f in up to 65% ee, pymoxs 2a-e gave somewhat lower enantioselectivities (up to 53% ee). Both classes of ligands produced trans-cyclopropanes 23a-f as the major isomer, although with modest diasteroselectivities (56 : 44 to 78 : 22). A structure-stereoselectivity relationship study of ligands 1 and 2 identified the chiral biaryl axis as being mostly responsible for the enantioselective performances of these ligands.
authors.affiliation: Laboratoire de Chimie Organique Fine et Hétérocyclique, UMR 6014, IRCOF, CNRS, Université et INSA de Rouen, B.P. 08, F-76131, Mont-Saint-Aignan Cédex, France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Bouet
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Deguest
authors.forename: Barbara
authors.initials: B
authors.lastname: Heller
authors.forename: Cyril
authors.initials: C
authors.lastname: Papamicaël
authors.forename: Georges
authors.initials: G
authors.lastname: Dupas
authors.forename: Sylvain
authors.initials: S
authors.lastname: Oudeyer
authors.forename: Francis
authors.initials: F
authors.lastname: Marsais
authors.forename: Vincent
authors.initials: V
authors.lastname: Levacher