Chiral 1,2-bis(phosphetano)ethanes

Optically pure 1,2-bis(phosphetano)ethanes 3 (BPE-4) have been prepared from 1,2-bis(phosphino)ethane and the cyclic sulfates of symmetrical anti-1,3-diols. Diphosphine 3c (R=cyclohexyl) is an easily accessible, air-stable chiral ligand. Its suitability to the ruthenium-catalysed hydrogenation of functionalised ketones has been examined by using several catalyst precursors. Significant enantiomeric excesses were obtained. A ruthenium complex containing two coordinated diphosphines 3c was characterised by X-ray diffraction studies.