Kinetic resolution, chiral poisoning

Complete enantiomer discrimination and asymmetric deactivation of the racemic XylBINAP-RuCl2(dmf) ( )-7b using DM-DABN as a chiral poison are shown to be effective in the kinetic resolution of 2-cyclohexenol (Scheme 8.9). Use of just a 0.5 molar amount of (5)-DM-DABN relative to ( )-7b gives enantiopure (S)-2-cyclohexenol, which is kinetically resolved in the same conversion as enantiopure 7b. Indeed, the relative rate of hydrogenation of (R)- versus (5)-2-cyclohexenol in the presence of only a 0.5 molar amount of (5)-DM-DABN relative to ( )-7b is significantly large (kf/kg = 102). The combination of ( )-7b with (S)-DM-DABN also gives 99.3% ee of (R)-methyl 3-hydroxybutanoate quantitatively... 

A chiral poison will destroy part of the racemic ligand or catalyst, in situ, by kinetic resolution. The remaining enantioenriched material will then act as the chiral catalyst. Chiral activation of a catalyst, on the other hand, generates a new... 

The resolution of racemic secondary allyl alcohols can be performed in the presence of certain ruthenium chiral catalysts through enantioselective asymmetric hydrogenation [811, 881], Chiral poisoning also works in such kinetic resolutions. For example, hydrogenation of 2-cyclohexenol under ( )-binap-Ru catalysis in the presence of (II , 25)-ephedrine 1.61 (10 equiv) provides unreacted (J )-2-cydo-hexenol in 95% ee after 60% conversion [857],... 

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