Enantioselective copper-catalysed 1,4-addition of diethylzinc to cyclohexenone using chiral diphosphite ligands

Bulky diphosphite ligands derived from ribo- and xylofuranose were tested in the copper asymmetric catalytic addition of diethylzinc to 2-cyclohexenone. The xylose derivatives provide enantiomeric excesses in the range of 22-53%. We also describe the preparation of the ribofuranose diphosphite ligands.