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 -diazoacetate with aldimine was accelerated by a salt-containing chiral phosphoric acid and hence chiral metal phosphate presumably functioned as an active catalyst.
- asymmetric catalysis
- Friedel-Crafts reaction