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 = 30 psi, 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.
|Data di pubblicazione:||2004|
|Titolo:||Process-scale preparation of enantiomerically pure g-lactones by asymmetric hydrogenation of g-ketoesters and comparative tests of the sensory properties of some antipodes|
|Digital Object Identifier (DOI):||10.1016/j.tetasy.2004.06.024|
|Codice identificativo ISI:||WOS:000223219400031|
|Codice identificativo Scopus:||2-s2.0-3843104976|
|Appare nelle tipologie:||Articolo su Rivista|