New cascade reactions in chiral Brønsted acid catalysis

Chiral phosphoric acids are belonging to be one of the most powerful classes in the broad field of organocatalysis. Over the last decade, chiral Bronsted acids have been introduced in asymmetric synthesis and were successfully employed in numerous transformations for the assembly of enantioenriched compounds. Their advanced performances are due to their properties as bifunctional catalysts, simultaneously lowering the LUMO of the electrophiles via protonation and activationg the nucleophiles via their Lewis basic site. However, they can also perform exclusive protonation to form contact ion-pairs with electrophiles which leads to high stereocontrol. Furthermore, chiral phosphoric acids have shown versatile properties when involved in dual catalytic systems. In addition, N-triflylphosphoramides are more acidic compared with the corresponding phosphoric acids. Since their first introduction by Yamamoto's group, their high acidity has permitted a range of functional groups to take part in new asymmetric reactions.