Catalytic asymmetric aldol reactions in aqueous media--a 5 year update

Asymmetric reactions in water and in aqueous solutions have become an area of fast growing interest recently. Although for a long time neglected as a medium for organic reactions, water has attracted attention as the most widely distributed solvent in the world. Indeed, water is the solvent used by nature for biological chemistry including aldol reactions being essential for glycolysis, gluconeogenesis and related processes. Consequently, artificial catalysts designed and used for aldol reactions in water can be promising for the synthesis of enantiopure molecules and are also important for the understanding of complex chemistry of life. This tutorial review summarizes recent developments in the area of aqueous asymmetric aldol reactions highlighting two fundamental directions--development of water compatible chiral Lewis acids and amine-based organocatalysts.