Catalytic asymmetric synthesis of both enantiomers of 4-substituted 1,4-Dihydropyridines with the use of bifunctional Thiourea-Ammonium salts bearing different counterions

Abstract

Organoammonium salts composed of a Brønsted acid and an anilinothiourea promoted the Michael addition of β-keto esters and α,β-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 HBF4 with the same bifunctional thiourea, both enantiomers of 4-substituted 1,4-dihydropyridine were synthesized from the same starting materials. © 2010 licensee MDPI, Basel, Switzerland.