A reliable methodology, applicable on a process-scale level, for producing enantiomerically pure chiral γ-lactones by enantioselective hydrogenation of γ-ketoesters, followed by cyclisation of the resulting γ-hydroxyesters, has been developed. The multi-step procedure was transformed into a one-pot reaction. A very efficient chiral Ru-complex, based on the biheteroaromatic diphosphine ligand tetraMe-BITIOP, was developed as a catalyst, capable of coupling fast kinetics with high stereoselection levels. Its structure was fully elucidated through 31P NMR, EPR and X-ray single-crystal analyses. The optimal experimental conditions are as follows: hydrogen pressure=30psi, S/C ratio=2000, 30% in weight substrate concentration. Yields are quantitative and enantiomeric excesses in the range 98-99.9%. Sensorial tests on the antipodes of two γ-lactones demonstrated the very different properties of the enantiomers.
Process-scale preparation of enantiomerically pure gamma-lactones by aymetric hydrogenation of gamma-ketoesters and comparative tests of the sensory properties of some antipodes / T. Benincori, S. Rizzo, T. Pilati, A. Ponti, M. Sada, E. Pagliarini, S. Ratti, G. Cementano, L. De Ferra, F. Sannicolò. - In: TETRAHEDRON-ASYMMETRY. - ISSN 0957-4166. - 15:14(2004), pp. 2289-2297. [10.1016/j.tetasy.2004.06.024]
Process-scale preparation of enantiomerically pure gamma-lactones by aymetric hydrogenation of gamma-ketoesters and comparative tests of the sensory properties of some antipodes
E. Pagliarini;S. Ratti;F. Sannicolò
2004
Abstract
A reliable methodology, applicable on a process-scale level, for producing enantiomerically pure chiral γ-lactones by enantioselective hydrogenation of γ-ketoesters, followed by cyclisation of the resulting γ-hydroxyesters, has been developed. The multi-step procedure was transformed into a one-pot reaction. A very efficient chiral Ru-complex, based on the biheteroaromatic diphosphine ligand tetraMe-BITIOP, was developed as a catalyst, capable of coupling fast kinetics with high stereoselection levels. Its structure was fully elucidated through 31P NMR, EPR and X-ray single-crystal analyses. The optimal experimental conditions are as follows: hydrogen pressure=30psi, S/C ratio=2000, 30% in weight substrate concentration. Yields are quantitative and enantiomeric excesses in the range 98-99.9%. Sensorial tests on the antipodes of two γ-lactones demonstrated the very different properties of the enantiomers.
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