Preparation of enantiomerically pure [3]ferrocenophane-based chelate bis-phosphane ligands and their use in asymmetric alternating carbon monoxide/propene copolymerization

Patrick Liptau, Ludger Tebben, Gerald Kehr, Roland Fröhlich, Gerhard Erker, Frank Hollmann, Bernhard Rieger

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46 Scopus citations

Abstract

An intramolecular Mannich reaction (HNMe2, TiCl4) was used to convert 1,1′-diacetylferrocene to the unsaturated amino[3]ferrocenophane 2. Subsequent hydrogenation gave 3. To obtain enantiomerically pure chelate P,P-[3]ferrocenophane ligands the readily available pure dimethylamino[3]ferrocenophane enantiomers (R,R)-3 and (S,S)-3 each were treated with butyllithium followed by chlorodiphenylphosphane to yield the chelate P,N-[3]ferrocenophanes (R,R,Rpl)-10 and (S,S,S pl)-10, respectively. Their treatment with HPPh2 in glacial acetic acid resulted in substitution of the -NMe2 group by -PPh2 with overall retention of configuration to yield (R,R,R pl)-11 and (S,S,Spl)-11, respectively (both characterized by X-ray diffraction). Similarly, the reaction of (R,R,Rpl)-10 or (S,S,Spl)-10 with dicyclohexylphosphane/HOAc yielded the pure (R,R,Rpl)-12 and (S,S,Spl)-12 enantiomers, respectively. Both these compounds were also characterized by X-ray crystal structure analyses. (R,R,Rpl)-12 was employed in catalytic asymmetric hydrogenation and also in asymmetric alternating carbon monoxide/propene copolymerization. A catalyst that was generated in situ from the chelate P,P-[3]ferrocenophane ligand and palladium acetate gave the CO/propene alternating copolymer with a good activity and high asymmetric induction. The catalyst derived from the reaction of (R,R,Rpl)-11 with [Rh(cod) 2]BF4 was employed in the enantioselective hydrogenation of dimethyl itaconate (DMI) (13, ca. 95% ee, R-configured product) and methyl α-acetamidocinnamate (MAC) 14 (ca. 24% ee, R-configured product).

Original languageEnglish
Pages (from-to)1909-1918
Number of pages10
JournalEuropean Journal of Organic Chemistry
Issue number9
DOIs
StatePublished - 29 Apr 2005
Externally publishedYes

Keywords

  • Asymmetric catalysis
  • Chiral ferrocenophane
  • Copolymerization

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