When 4-(methylsulfonyl)cinnoline (I) and potassium cyanide are reacted in dimethyl sulfoxide, 4-cinnolinecarbonitrile (IV) is produced quantitatively at a reaction temperature of 20°C, while the temperature us raised to 100°C, 4, 6-cinnolinedicarbonitrile (V) is produced. (Table I). V is also prepared by reacting both IV and potassium cyanide in dimethyl sulfoxide at 100°C. Therefore, the reaction process is suggested as is shown in Chart 2. The determination of the structure V is made by means of NMR spectrum (Table II).