New chiral ligands for the enantioselective catalysis with transition metal complexes

We have prepared new ligands based on the combination of the atropisomeric chirality with the chirality of stereogenic carbon atoms.
The ligands are prepared according to the scheme 1, and are obtained in good yield by the condensation of one or two optically pure (R) or (S) 1,1’Binaphthyl[1] group and chiral not racemic aminoalcohols derived from the “chiral pool”.
The aminoalcohols of choice are -N-ethylamino buthanol and 2-Pyrrolidinemethanol; with these chiral substrates we have prepared two different types of ligands: 6 and 7.
By a combination of NMR techniques we have fully characterized the ligands and the correspondent Rh(I), Pd(II), Pt(II) complexes.
Rhodium complexes based on type 6 and type 7 ligands have demonstrated to be active catalysts in the asymmetric hydrogenation of N-protected dehydroaminoacids.

[1] We are indebted to Prof. F. Faraone and with his coworker C.G. Arena for the detailed description of the preparation of 1,1’Binaphtyl-2,2’ diylphosphite cloride.