This chapter presents a complementary compilation of the synthetic routes of the fused and spiro pyridine derivatives via multicomponent reaction using malononitrile as one of the key reagents. It describes the synthesis of hydroisoquinoline derivatives by multicomponent reaction of glutaraldehyde and malononitrile with β-keto amides under microwave irradiations in the presence of a 20 mol" sodium hydroxide (NaOH) via a C-C bond cleavage reaction. Pyrido[2,3-a]carbazoles were prepared in good yields by the multicomponent reaction of 6-methyl-2,3,4,9-tetrahydro-1H-carbazol-1-one, benzaldehyde, malononitrile, and ammonium acetate using l-proline as organocatalyst in dry ethanol. The chapter discusses a very interesting procedure for the synthesis of polysubstituted pyrido[1,2-a]benzimidazole derivatives by four-multicomponent reaction of pyridine or 3-picoline, chloroacetonitrile, malononitrile, and aromatic aldehyde. It provides a synthesize of thiazolo[3,2-a]pyridines 27 using a multicomponent reaction between aromatic aldehydes, 2-nitromethylenethiazolidine, and malononitrile, in the presence of base Et3N under mild reaction conditions with high yields of product.
