1,2-Dicyanocyclobutene

Used as reactive dienophile in [4 + 2], [3 + 2], and [2 + 2] Diels-Alder additions; reactive diene in [4 + 2] inverse electron demand Diels-Alder additions upon in situ thermolytic cleavage to 2,3-dicyanobutadiene.

1,2-Dicyanocyclobutene may be prepared by several methods. The most convenient involves the  chlorination of 1,2-dicyanocyclobutane with Phosphorus(V) Chloride followed by dechlorination with Triethylamine in refluxing benzene to give the reagent in good yield.