Diazocines, Beckmann rearrangement

Beckmann rearrangement of anthraquinone dioximes leads to 1.5-diazocine systems, a reaction which indirectly proves the C2-symmetry of the starting material.51,52 The reaction is induced preferentially by heating in polyphosphoric acid. 

A number of 1,4-diazocines have reacted to form imidazoles and fused-ring analogs. Beckmann rearrangement of the dioxime 171 yielded isoindolo-benzimidazole 172 (R = Cl, R = H) or 172 (R = H, R = Cl), most likely via rearrangement of an initially formed dichloro- 57 (57JCS1900). Dibenzo-diazocinedione 57, when heated with phosphorus pentachloride, afforded an... 

---