Pyridinium 1,1'-binaphthyl-2,2'-disulfonates as highly effective chiral Brønsted 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 Brønsted acid-base organocatalysts in situ.