Asymmetrische katalytische Hydrierung von Acylamino-acrylsaeureethylester und (Z)-Acylamino-zimtsaeuremethylester mit Rhodium-(Diop-Derivat)-Komplexen als Katalysatoren. Einfluss der Einfuehrung zweier Bisarylphosphino-Gruppen mit unterschiedlichen Elektronendichten an den Phosphorato...

Article abstract of DOI:10.1016/0022-328X(89)87036-6

(R,R)-Diop was modified by the introduction of two bis-arylphosphino groups <(4-X-phenyl)2P- and (4-Y-phenyl)2P-; X, Y different substituents> of different charge densities on the phosphorus atoms, so that unsymmetrically substituted diop derivatives were formed.The effects of the substituents and the loss of the two-fold rotation axis were examined on the basis of the hydrogenation of ethyl α-acylamino-acrylate (AAEE) and (Z)-methyl α-acylamino-cinnamate (AZME) with ⁺BF4^- (ns-Rh) as the catalytic precursor with the least steric influence by the substituents.We reported recently the results of the hydrogenation of the same substrates but with ⁺BF4^- (s-Rh) as the catalytic precursor.The electronic and steric effects of the substituents we had found by the hydrogenation experiments with the s-Rh (1) affected the optical yields with the ns-Rh nearly additively.This means that the optical yield obtained with an ns-Rh was fairly consistent with the value calculated by averaging the optical yields of the corresponding s-Rh.Surprisingly the electronic and in special cases the steric features of the substituents are sufficient to explain the results.The loss of the two-fold rotation had no significant effect.The effects of solvation were not examined.