An efficient Hantzsch synthesis of 1,4-dihydropyridines using p-toluenesulfonic acid under solvent-free condition

An efficient Hantzsch synthesis of various substituted 1,4-dihydropyridines from an aldehyde, a beta-dicarbonyl compound and ammonium acetate using p-toluenesulfonic acid in a solvent-free condition in the absence of any other co-catalyst is described. The process is simple and environmentally benign and the catalyst is commercially available and inexpensive. This method has the advantages of excellent yield (80-96%) and short reaction time (5-20 min.). Irradiation of a typical 1,4-dihydropyridine leads to the corresponding pyridine.