Preparation of new axially chiral bridged 2,2′-bipyridines and pyridyl monooxazolines (pymox). Evaluation in copper( i )-catalyzed enantioselective cyclopropanation

Alexis Bouet (1) , Barbara Heller (2) , Cyril Papamicaël (1) , Georges Dupas (1) , Sylvain Oudeyer (1) , Francis Marsais (1) , Vincent Levacher (1)

1 COBRA - Chimie Organique et Bioorganique : Réactivité et Analyse
2 LIKAT Rostock - Leibniz-Institut für Katalyse

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.

Domaines: Chimie organique

Alexis Bouet, Barbara Heller, Cyril Papamicaël, Georges Dupas, Sylvain Oudeyer, et al.. Preparation of new axially chiral bridged 2,2′-bipyridines and pyridyl monooxazolines (pymox). Evaluation in copper( i )-catalyzed enantioselective cyclopropanation. Organic & Biomolecular Chemistry, 2007, 5 (9), pp.1397-1404. ⟨10.1039/b701549f⟩. ⟨hal-02278796⟩