Yet Another Direct Aldol Reaction in Water

Significance

The authors report two proline-derived organocatalysts capable of mediating the direct asymmetric aldol reaction of ketones with aldehyde acceptors in high enantioselectivities and with low catalyst loadings in an aqueous medium. Both water and brine may be utilized as solvents. The reaction is quite general with regard to the aldehyde donors; not only aromatic, but also some α-disubstituted aliphatic aldehydes have been employed. Good yields are reported alongside excellent enantioselectivities, and the syn/anti ratios are very good. The authors reason that their reaction takes place under biphasic conditions, with a hydrophobic assembly of catalyst and substrate at the center of reactivity.