Chiral Complexes of RhI Containing Binaphthalene-Core P,S-Heterobidentate Ligands − Synthesis, Characterization, and Catalytic Activity in Asymmetric Hydrogenation of α,β-Unsaturated Acids and Esters

✍ Scribed by Serafino Gladiali; Fabrizia Grepioni; Serenella Medici; Antonio Zucca; Zoltán Berente; László Kollár

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 137 KB
• Volume: 2003
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/ejic.200390077

✦ Synopsis

Abstract

The enantiopure complexes 3a and 3b [Rh(NBD)(P,S)]^+^BF~4~^−^ [P,S = (S)‐2‐(diphenylphosphanyl)‐2′‐(methylthio)‐1,1′‐binaphthalene (a); (S)‐2‐(diphenylphosphanyl)‐2′‐(isopropylthio)‐1,1′‐binaphthalene (b)] have been prepared from [Rh(NBD)(THF)~2~]^+^BF~4~^−^ by reaction with a stoichiometric amount of the appropriate P,S‐heterobidentate ligand. Single‐crystal X‐ray analysis of the S‐methyl derivative shows that the seven‐membered chelate ring is locked in a boat‐like conformation with the methyl group in the equatorial position. Variable‐temperature NMR measurements confirm that this conformation is maintained in solution and that the dynamic behaviour displayed by the complex is due to pseudo‐rotation of the diolefin. Complexes 3 have been tested in the asymmetric hydrogenation of α,β‐unsaturated acids and esters. Enantioselectivities of up to 60% ee have been recorded. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)