text: About a decade later, Jurkauskas and Buchwald also utilized dynamic kinetic resolution towards the hydrogenation of conjugated systems.   1,4 addition to cyclic enones is quite common in many reaction schemes, however asymmetric reductions in the presence of an easily epimerizable center adds to the complexity when trying to modify only one center. Through the use of a copper catalyzed reaction however, Buchwald was able to obtain 1,4 reduction in great enantiomeric excess (ee).  In order to achieve a high rate of epimerization, a strong bulky base like sodium t-butoxide was used to ensure rapid equilibrium.
  Copper proved to be an excellent metal in this reaction due to its ability to complex with the oxygen when the hydrogen was added. Being a soft metal, copper greatly prefers 1,4 addition over 1,2 addition, with the alkene being a softer more polarizable electrophile. Again, BINAP became the ligand of choice due to its steric selectivity, lowering the transition state energy of starting material in the left column.  In addition, PMHS was used as a relatively less reactive silane.  This prevented loss of ee before deprotection with tetra-n-butylammonium fluoride (TBAF).