The bisolefins partly block the active catalyst by coordination to rhodium. This was demonstrated experimentally by prehydrogenation of the precatalyst (in the absense of the prochiral olefin) and subsequent addition of prochiral substrate, or by using COD-free complexes. Only after complete hydrogenation of the bisolefin ligand does the full amount of catalyst become accessible for asymmetric hydrogenation. On the basis of the experimentally confirmed Michaelis-Menten kinetics the rate constants of the hydrogenation of COD and NBD by different chiral catalysts were determined (Table 1).All investigated catalysts hydrogenated NBD faster than COD, in some cases considerably faster. Additionally, rate constants which differ by up to a factor of 50, were obtained for the hydrogenation of a bisolefin with different catalysts. Generally, methanol was used as solvent, however, similar results were obtained in other solvents, e.g. THF (ligands 1 and 7 in Table 1).The induction period, observed for several catalysts (ligands 3, 4, 5), which accompanies the catalytic hydrogenation of NBD with COD complexes (Figure 1) indicates that the Michaelis constant (KM) for the COD hydrogenation is smaller than for the NBD hydrogenation.Rates of the hydrogenation of CODDJBD = 1 : l mixtures are lower than expected. Product analysis after
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