205195-47-7Relevant academic research and scientific papers
Enantioselective catalysis, XVIII [1] the influence of non-coordinated stereocenters on the enantioselective hydrogenation
Nagel, Ulrich,Roller, Christoph
, p. 211 - 223 (1998)
3,4-Bis{[2-(methyl-phenyl-oxophosphanyl)-ethyl]phenyl-phosphanyl} pyrrolidines have been synthesized by Michael Addition from the corresponding methyl-phenyl-vinyl-phosphane oxides and 3,4-bis(phenylphosphino)pyrrolidines. For purification of the ligands palladium complexes were used and with the enantiomerically pure ligands Rh complexes have been prepared. The catalyst has 6 stereogenic centers. In the hydrogenation of Z-α-acetamidocinnamic acid all six stereogenic centers have an influence on the enantioselectivity. The influence is strongest from the C stereocenters of the pyrrolidine ring. Less important are the stereogenic centers on the coordinated P atoms. The influence of the stereocenters on the non-coordinated P=O groups is the least, but it is not negligible. The ee values obtained with the ligands containing P=O groups are much lower than those obtained with ligands which are substituted only with aryl groups. Ketones are hydrogenated with only low ee's.
