The heterogeneous asymmetric direct aldol reactions between aldehydes (2-nitrobenzaldehyde, 2-methylpropanal) and ketones (acetone, cyclohexanone) in the presence of polystyrene (PS) resin supported di- and tripeptides were studied under otherwise identical experimental conditions at room temperature in batch reactor. For all three asymmetric aldol reactions reversal of enantiomeric excess was observed on H-Pro-Pro-Glu(OH)-PS catalyst (ee 39-50%) as compared to the H-Pro-Glu(OH)-PS catalyst (ee 52-95%). The determinant role of the conformation of the intermediate adducts held responsible for chiral induction is interpreted by quantum chemical calculations.
- Aldol reaction
- Asymmetric synthesis
- Heterogeneous catalysis
ASJC Scopus subject areas
- Process Chemistry and Technology
- Physical and Theoretical Chemistry