Studien zum Vorgang der Wasserstoffübertragung, 72 [1] Versuche zur enantioselektiven Homogenhydrierung von N-Acyl-α-aminozimtsäuren mit Rh(I)-Komplexen unter Verwendung neuer optisch aktiver Co-Katalysatoren/Studies on the Occurrence of Hydrogen Transfer, 72, [1] Investigation on the Enantioselective Homogeneous Hydrogenation of N-Acyl-α-aminocinnamic Acids with Rh(I)-Complexes Using New Optically Active Co-Catalysts
3 Optically active compounds of the type I and 15 optically active compounds of the type II were investigated as co-catalysts in the homogeneous hydrogenation of N-acyl-α-aminocinnamic acids using standard conditions. In the co-catalysts of the type I the phosphorus atom is the center of the asymmetry. In the representatives of type II the side chain is optically active and the three bonded phosphorus either achiral or optically active.The results of the homogeneous hydrogenation are deposited in the Tables I-IV. In the Tables I and IV the degree of the optical induction and the configuration of the excess enantiomer are determined using Rh/P-ratios 1:1,1 and 1:2,2. The Tables II and III show the results applying a Rh/P-ratio of 1:2,2. The observed degree of optical induction is low with the co-catalysts 1-18; only the co-catalyst 19 shows an optical induction of 68%. A change of the configuration of the excess enantiomer of N-benzoylphenylalanine formed by the homogeneous hydrogenation of N-benzoyl-α-cinnamic acid for the first time was observed by varying the Rh/P-ratio of the co-catalysts 14, 17 and 18 from 1:1,1 to 1:2,2.