Pyridinium 1,1′-Binaphthyl-2,2′-disulfonates as Highly Effective Chiral Bronsted Acid-Base Combined Salt Catalysts for Enantioselective Mannich-Type Reaction

We have established, for the first time, a practical synthesis of chiral 1,1'-binaphthyl-2,2'-disulfonic acid (BINSA 1) from inexpensive BINOL. An efficient enantioselective catalysis in the Mannich-type reactions of diketones and ketoester equivalents with aldimines was developed using chiral 1-achiral, 2,6-diarylpyridine (2) combined salts, which acted as convenient chiral tailor-made Bronsted acid-base organocatalysts in situ.