A series of new highly substituted isoquinoline derivatives was obtained from the reaction of 2‐(1‐substituted piperidin‐4‐ylidene)malononitrile, benzaldehyde and malononitrile or cyanoacetate in ionicliquid at 50°C. This novel procedure was different from the previous method in the synthesis of isoquinoline using pyridine fragment as reactant to construct benzene ring, and as well as had the advantages