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Planar chiral alkenylferrocene phosphanes: Preparation, structural characterisation and catalytic use in asymmetric allylic alkylation

Authors
Journal
Journal of Organometallic Chemistry
0022-328X
Publisher
Elsevier
Publication Date
Volume
693
Issue
3
Identifiers
DOI: 10.1016/j.jorganchem.2007.11.016
Keywords
  • Ferrocene
  • Phosphanes
  • Alkenes
  • Alkenylphosphanes
  • Palladium
  • Enantioselective Allylic Alkylation

Abstract

Abstract Planar chiral alkenylferrocene phosphanes, viz. ( S p)-[Fe(η 5-C 5H 3-1-PPh 2-2-CH CR 2)(η 5-C 5H 5)] (R = H, ( S p)- 2; Ph, ( S p)- 5) and ( S p)-[Fe(η 5-C 5H 3-1-PPh 2-2-( E)-CH CHR)(η 5-C 5H 5)] (R = Ph, ( S p)- 3; C(O)CH 3, ( S p)- 6; and CO 2CH 2CH 3, ( S p)- 7) have been prepared by alkenylation of ( S p)-2-(diphenylphosphanyl)ferrocenecarboxaldehyde and tested as ligands for enantioselective palladium-catalysed allylic alkylation of 1,3-diphenyprop-2-en-1-yl acetate with dimethyl malonate. All phosphanylalkenes formed active catalysts. However, the induced enantioselectivity was only poor to moderate [12–43% ee after 20 h at room temperature], with the ee’s and configuration of the preferred product strongly depending on the ligand structure. The catalytic results have been related to solution properties (NMR, ESI MS) and the solid-state structural data (X-ray diffraction) of [Pd(η 3-1,3-Ph 2C 3H 3){( S p)- 2-η 2:κ P}]ClO 4 (( S p)- 12), which represent a model of the plausible reaction intermediate.

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