Direct Catalytic Asymmetric Aldol Reactions Assisted by Zinc Complex in the Presence of Water

A combination of zinc triflate and chiral C₂‐symmetrical prolinamide ligand leads to high enantioselectivities in direct aldol reactions essentially assisted by water. The presence of 5 mol % of the catalyst affords an asymmetric intermolecular aldol reaction between unmodified ketones and aldehydes to give anti‐products with excellent enantioselectivities ranging from 86–98 % ee. The same bis(prolinamide) ligand is found to catalyze the direct aldol reactions in the presence of water (or in water) with excellent stereocontrol and furnish the corresponding aldols in up to 99 % ee. For the demonstrated catalytic systems organic solvent‐free conditions are applied.