Reaction of diethyl azulene-1,3-dicarboxylate with potassium cyanide in dimethoxyethane gave diethyl 4-cyano-, 6-cyano-, and 4,6-dicyanoazulene-1,3-dicarboxylates. This cyanation involved addition of a cyanide ion to the seven- membered ring of azulene to form a cyclopentadienide ion, followed by oxidation.
Relation:
Journal of the Chinese Chemical Society=中國化學會會誌 42(5), pp.861-864
