Chiral Phosphino- and (Phosphinooxy)-Substituted N-Heterocyclic Carbene Ligands and Their Application in Iridium-Catalyzed Asymmetric Hydrogenation

• Published in: Helvetica chimica acta Vol. 89; no. 8; pp. 1559 - 1573
• Main Authors: Nanchen, Steve, Pfaltz, Andreas
• Format: Journal Article
• Language: English
• Published: Zürich WILEY-VCH Verlag 01.08.2006; WILEY‐VCH Verlag; Wiley
• Subjects: asymmetric; Asymmetric catalysis; Asymmetric hydrogenation; Catalysis; Chemistry; Chemistry, Multidisciplinary; Chiral ligands; Hydrogenation; Hydrogenation, asymmetric; Iridium complexes; Physical Sciences; Science & Technology; ALLYLIC ALKYLATION; ALKENES; OLEFIN METATHESIS; OXAZOLINE LIGANDS; ENANTIOSELECTIVE HYDROGENATION; COMPLEXES
• ISSN: 0018-019X; 1522-2675
• DOI: 10.1002/hlca.200690157

Enantiomerically pure iridium complexes with phosphino‐ and (phosphinooxy)‐substituted N‐heterocyclic carbene (NHC) ligands were synthesized. Investigation of their electronic properties showed a similar trans influence of the phosphino (or phosphinooxy) and the NHC units. The complexes were tested in iridium‐catalyzed hydrogenation. While low conversions were observed with unfunctionalized olefins, the catalysts proved to be suitable for hydrogenation of the α,β‐unsaturated ester 20, allylic alcohol 21, and imine 22. The enantioselectivities were, however, moderate.