Chiral Calix[4]arene-Based Diphosphites as Ligands in the Asymmetric Hydrogenation of Prochiral Olefins

摘要

Chiral calixarene-based diphosphite ligands 3a-d have been obtained via lower-rim functionalisation of the p-tert-butyl-calix[4]arene core. High enantiomeric excesses (up to 94%) and good activities were obtained in the rhodium-catalyzed asymmetric hydrogenation of prochiral olefins with TADDOL-containing diphosphites 3c,d. This is the first example of chiral calix[4]arene-modified ligands that induce high enantioselectivity in metal-catalysed asymmetric reactions.