Asymmetric organocatalysis:

• Houk and List (2003):
  • Proline-mediated asymmetric intermolecular aldol reactions
  • One carbonyl compound functionalised into an enamine using enantiopure proline (green)
  • reacts with a second carbonyl to form an aldol
• the catalytic effect originates from intermolecular proton transfer
• Two new stereocentres created (red bond): (S,R), (S,S), (R,S), (R,R).
• One is produced in high enantiomeric excess (ee)

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  ...... Why? .......

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