Catalytic asymmetric synthesis of both enantiomers of 4‑substituted 1,4-dihydropyridines with the use of bifunctional thiourea-ammonium salts bearing different counterions.

Organoammonium salts composed of a Brønsted acid and an anilinothiourea promoted the Michael addition of ß-keto esters and α,ß-unsaturated aldehydes in the presence of primary amines to give functionalized 1,4-dihydropyridines enantioselectively. With the use of the different Brønsted acids such as DFA and HBF(4) with the same bifunctional thiourea, both enantiomers of 4-substituted 1,4-dihydropyridine were synthesized from the same starting materials.