Intermolecular Aldol Reactions in Enamine Catalysis

Entry R R R Catalyst (mol%) Conditions Yield (%) dr [anti syn) ee %) Reference 

2 CH2OH OH 4-NO2QH4 13 (20) PBS (phosphate buffered saline), rt, 24-72h Trace 50 50 0 14  

The commercially available acetaldehyde (34) serves as a donor for aldol reactions, but undesirable side products are generally formed because of its very high degree of reactivity. In 2002, the (S)-proline catalyzed self-aldol reaction of this acetaldehyde was reported the reaction yielded over-reacting (-F)-(5S)-hydroxy-(2 )-hexenal with 57 to 90% ee [21]. The synthetically challenging i-hydroxy a-unsubstituted 

---