P-Stereogenic Ferrocene-Based (Trifluoromethyl)phosphanes: Synthesis, Structure, Coordination Properties and Catalysis

• Published in: European Journal of Organic Chemistry 2011-01, Vol.2011 (1), p.78-87
• Main Authors: Sondenecker, Aline, Cvengroš, Ján, Aardoom, Raphael, Togni, Antonio
• Format: Article
• Language: English
• Subjects: Asymmetric catalysis; Chemistry; Chiral auxiliaries; Coordination compounds; Electrophilic trifluoromethylation; Exact sciences and technology; Ferrocene; Inorganic chemistry and origins of life; Ligand design; Organic chemistry; Organometalloidal and organometallic compounds; P derivatives; Phosphanes; Preparations and properties
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201001162

Diastereoselective ortho‐hydroxymethylation of (R)‐(1‐ferrocenylethyl)dimethylamine and Brønsted‐acid‐mediatednucleophilic substitution with phenyl(trifluoromethyl)phosphane affords an epimeric mixture of P‐stereogenic amine–phosphanes 4a and 4b, which are readily separated by crystallization from methanol. Subsequent substitution of the dimethylamino group with diphenylphosphane occurs without epimerization, yielding novel bis(phosphanes) 1a and 1b. These bis(phosphanes) combine three elements of chirality (C‐central, P‐central and planar) and bear a trifluoromethyl group at a stereogenic phosphorus atom. Their complexes with transition metals (Pd, Rh, Ir) were studied and characterized by means of NMR techniques and X‐ray crystallographic analyses, and the bidentate ligands proved efficient in stereoselective catalysis. Enantiomerically pure ferrocene‐based bis(phosphane) ligands combining three elements of chirality (C‐central, P‐central and planar) and bearing a trifluoromethyl group at a phosphorus atom were synthesized. Their complexes with transitionmetals were characterised and examined in an enantioselective Rh‐catalyzed hydrogenation. The impact of the trifluoromethylated stereogenic phosphorus atom is described.