Metal-Free Chiral Phosphoric Acid or Chiral Metal Phosphate as Active Catalyst in the Activation of N-Acyl Aldimines

Whether metal-free chiral phosphoric acid or chiral metal phosphate functions as an active catalyst was confirmed in three reactions. In the aza-Friedel-Crafts and aza-ene-type reactions, a metal-free chiral phosphoric acid, namely, a chiral Bronsted acid, was verified to be the active catalyst. In contrast, the substitution reaction of a-diazoacetate with aldimine was accelerated by a salt-containing chiral phosphoric acid and hence chiral metal phosphate presumably functioned as an active catalyst.