New P-Chirogenic tert.-butyl-xantphos ligands and their application in asymmetric hydrogenation and alkylation

Abstract The synthesis of a broad library of new P-chirogenic Xantphos ligands is reported. A special feature is 2,7-di-tert.-butyl substituents in the backbone which requires the modification of the original synthetic approach. In comparison to related ligands reported formerly the substitution has a considerable influence on the results (yield and % e.e.) of metal catalyzed reactions, e.g. asymmetric rhodium catalyzed hydrogenation of isophorone and the palladium catalyzed alkylation, respectively.