An efficient one-pot synthesis of 1,4-dihydropyridine derivatives through Hantzsch reaction catalysed by melamine trisulfonic acid

The classical Hantzsch reaction is one of the simplest and most economical methods for the synthesis of biologically important and pharmacologically useful 1,4-dihydropyridine derivatives. Melamine trisulfonic acid (MTSA) under thermal condition is proven to act as a very efficient catalyst for a one-pot synthesis of 2-amino-4-phenyl-3-cyano-7,7-dimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline derivatives in excellent yields from aldehydes, dimedone, malononitrile and ammonium acetate under solvent-free conditions. The present environmentally benign procedure for the synthesis of 1,4-dihydropyridines is suitable for library synthesis and it will find application in the synthesis of potent biologically active molecules. The process presented here is operationally simple, environmentally benign and has excellent yield. Furthermore, the catalyst can be recovered conveniently and reused efficiently.