Chiral calixarene-based diphosphite ligands 3a–d have been obtained via lower-rim functionalisation of the p-tert-butylcalixarene core. High enantiomeric excesses (up to 94 %) and good activities were obtained in the rhodium-catalyzed asymmetric hydrogenation of prochiral olefins withTADDOL-containing diphosphites 3c,d. This is the first example of chiral calixarene-modified ligands that induce high enantioselectivity in metal-catalysed asymmetric reactions.
Chiral calixarene-based diphosphites as ligands in the asymmetric hydrogenation of prochiral olefins
Eur. J. Inorg. Chem. 2007, 4587-4591.