Interconversion of diastereomeric complexes involved in Rh(I)‐catalyzed asymmetric hydrogenation: A (31P, 31P) EXSY NMR study
- 1 March 1993
- journal article
- research article
- Published by Wiley in Magnetic Resonance in Chemistry
- Vol. 31 (3) , 293-298
- https://doi.org/10.1002/mrc.1260310316
Abstract
Rhodium(I) complexes containing chiral chelating diphosphines, e.g. R,R‐dipamp [(R,R)‐1,2‐bis(o‐methoxy‐phenylphenylphosphino)ethane] or S,S‐chiraphos [(2S,3S)‐bis(diphenylphosphino)butane] and a prochiral olefin, e.g. methyl (Z)‐α‐acetamidocinnamate (mac), form diastereomeric complexes which differ only in which enantiotopic face of the olefin is bound to rhodium and can be observed by 31P NMR. The interconversion of the two diastereomers has been observed with (31P,31P)‐{1H} 2D EXSY techniques for various mixing times, Tm, and in three different solvents (CD2Cl2, CD3OD and CD3COCD3). The results clearly demonstrate that both inter‐ and intramolecular ligand exchange processes are occurring, and that diastereomeric interconversion cannot proceed exclusively by complete mac dissociation followed by readdition to the opposite enantiotopic olefin face. The new results are consistent with previous DANTE NMR experiments. The differing results in CD2Cl2, CD3OD and CD3COCD3 solutions suggest the possibility of solvent involvement in the rate‐limiting step of ligand exchange. The 2D EXSY method appears to be the method of choice for elucidating the qualitative exchange pathway of this complex system.Keywords
This publication has 12 references indexed in Scilit:
- Kinetics and mechanism of catalysis of the asymmetric hydrogenation of .alpha.,.beta.-unsaturated carboxylic acids by bis(carboxylato) {2,2'-bis(diphenylphosphino)-1,1'-binaphthyl}ruthenium(II), [RuII(BINAP) (O2CR)2]Journal of the American Chemical Society, 1991
- Application of two-dimensional NMR to kinetics of chemical exchangeChemical Reviews, 1990
- Asymmetric hydrogenation of methyl (Z)-.alpha.-acetamidocinnamate catalyzed by [1,2-bis(phenyl-o-anisoyl)phosphino)ethane]rhodium(I): kinetics, mechanism and origin of enantioselectionJournal of the American Chemical Society, 1987
- A systematic approach to the suppression of J cross peaks in 2D exchange and 2D NOE spectroscopyJournal of Magnetic Resonance (1969), 1985
- Asymmetric Catalytic Hydrogenation: Mechanism and Origin of EnantioselectionPublished by Elsevier ,1985
- Longitudinal two-spin order in 2D exchange spectroscopy (NOESY)Journal of Magnetic Resonance (1969), 1984
- Asymmetric Hydrogenation Reactions Using Chiral Diphosphine Complexes of RhodiumPublished by Springer Nature ,1983
- Identification of the enantioselective step in the asymmetric catalytic hydrogenation of a prochiral olefinJournal of the American Chemical Society, 1980
- Interception and characterization of a hydridoalkylrhodium intermediate in a homogeneous catalytic hydrogenation reactionJournal of the American Chemical Society, 1980
- Intermediates in homogeneous catalytic hydrogenation. The crystal and molecular structure of the methyl(Z)-α-acetamodicinnamate adduct of 1,2-bis(diphenylphosphino)ethanerhodium(I)Inorganica Chimica Acta, 1979