A strategy for the stereoselective synthesis of unsymmetric atropisomeric ligands: preparation of NAPhePHOS, a new biaryl diphosphine.
MeO-NAPhePHOS represents the first example of a new series of atropisomeric diphosphines bearing heterotopic biaryl moieties. The key step of its synthesis is the diastereoselective, intramolecular, Cu(I)-promoted coupling of 1-iodonaphthol and 2-iodo-3-methoxyphenol connected by a chiral tether. (R,R)-2,4-Pentanediol is used as the chiral auxiliary in this highly selective reaction that leads to a single enantiomer of the title diphosphine. In the Ru-promoted hydrogenations of carbonyl derivatives, NAPhePHOS affords enantioselectivity levels fully comparable to those of the C(2)-symmetrical analogues, BINAP and MeO-BIPHEP respectively, thus showing that the lack of C(2) symmetry is not detrimental to the catalytic properties of atropisomeric ligands in these hydrogenation reactions.
Laboratoire de Synthèse Sélective Organique et Produits Naturels ENSCP-11, rue Pierre et Marie Curie, 75231 Paris Cedex 05 France.marinet@ext.jussieu.fr
Guillaume
G
Michaud
Michel
M
Bulliard
Louis
L
Ricard
Jean-Pierre
JP
Genêt
Angela
A
Marinetti