text: In addition to hydrogenation reactions, other bonds have been formed using DKR and are highly successful.  The aldol reaction has been extensively researched primarily because of the inherent challenge of forming a carbon-carbon bond.  Ward and colleagues have been able to use the proline-catalyzed aldol reaction in tandem with dynamic kinetic resolution to obtain a high enantioselective reaction.
  In this reaction proline catalyzes the reaction through creation of an enamine intermediate that is highly nucleophilic. The acid group on the catalyst helps facilitate the carbon-carbon bond formation by coordinating with the aldehyde oxygen.  This greatly improves stereoselectivity and yield.  Ward and his associates also found that by adding trace amounts of water to the DMSO solvent, it greatly increase the yield of the reaction, most likely by aiding proton transfer from proline to the newly forming alcohol.
  The selectivity for this product can best be explained by the Felkin model.  The cyclic (E)-enamine is able to undergo a favorable transition state where the aldehyde adopts an anti relationship relative to the incoming nucleophile, as well as a 1,2 syn relationship between the aldehyde and its adjacent ring system.  The transition state is shown above.