Optically active cyclopentadienyl and indenyl ligands obtained from lactic acid esters |
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Authors: | Richard Laï ,Florence Chanon,Martial Sanz,Jean-Claude Daran |
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Affiliation: | a Université Paul Cézanne, Av. Escadrille Normandie-Niémen, UMR CNRS 6180, F-13013 Marseille, France b Laboratoire de Chimie de Coordination, 205 Route de Narbonne, 31077 Toulouse Cedex 04, France |
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Abstract: | Asymmetric cyclopentadienes and indenes are easily prepared by nucleophilic attack of LiCp or LiInd on tosylate or triflate of ethyl (S)-(−) lactate. The selectivity of the reaction depends on the nature of the leaving group. This is particularly true in the case of the reaction of LiCp with sulfonates of ethyl (S)-(−) lactate. Indeed, only the monosubstituted cyclopentadiene lactate 2 is obtained from the triflate 6, whereas from the tosylate 1, besides 2 (20%) a 1,3-disubstituted cyclopentadiene lactate 3 is isolated (16.5%). From cyclopentadiene and indene lactate 2 and 7, optically active β-hydroxycyclopentadiene 10 and β-hydroxyindene 11 are obtained by reduction with LiAlH4. Two rhodium(I) complexes 14 and 15 have been synthesized from (R,S)-2-(cyclopentadienyl)N,N-dimethylpropanamide 12 and (S)-2-(cyclopentadiene)propan-1-ol 10, respectively. The molecular structure of these complexes has been determined. Analytical and preparative chiral HPLC have been used to determine the optical purity of the ligands and to isolate enantiopure cyclopentadienyl complexes from racemic or enantiomerically enriched rhodium(I) complexes. |
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Keywords: | Chiral cyclopentadienyl rhodium(I) complexes Ethyl (S)-(&minus ) lactate Cyclopentadiene and indene lactate Chirality Chiral HPLC X-ray diffraction |
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