Development of Synthetic Methodologies for the Multicomponent Synthesis of Biologically Important Polyhydroquinolines

Polyhydroquinoline is a privileged scaffold consisting of a 1,4-dihydropyridine moiety, which exhibits several pharmacological activities. The multicomponent approach for the synthesis of polyhydroquinolines involves a one-pot four-component condensation reaction of aldehyde, dimedone, ethylacetoacetate or ethylcyanoacetate and ammonium acetate. It involves protocols using various catalytic systems such as nanoparticles, organocatalysts, ionic liquids and inorganic materials. Biological functions as well as applications in other fields have increased interest in synthetic chemists towards the development of newer protocols for the construction of polyhydroquinolines. In this connection, an attempt has been made to summarize the recent methodologies for the synthesis of polyhydroquinolines in one article. The insights developed from this review will expand ideas of chemists for newer green synthetic strategies towards multicomponent synthesis of polyhydroquinolines.