Reaction of tetracyanoethylene with diselenium dichloride: a route to pyrrolo[2,3-c][1,2,6]selenadiazines

Tetracyanoethylene reacts with Se2Cl2, SO2Cl2 and catalytic BnEt3NCl in 1,2-dichloroethane heated at ca. 70 °C for 40 h to give 4,6-dichloropyrrolo[2,3-c][1,2,6]selenadiazine-5-carbonitrile (42%) and 4-chloro-6-oxo-6,7-dihydropyrrolo[2,3-c][1,2,6]selenadiazine-5-carbonitrile (30%). A chromatography free procedure allows isolation of 4,6-dichloropyrrolo[2,3-c][1,2,6]selenadiazine-5-carbonitrile in 70% yield. Regioselective displacement of the 6-chloro by O- and N-nucleophiles is demonstrated. Treatment of 4-chloro-6-morpholinopyrrolo[2,3-c][1,2,6]selenadiazine-5-carbonitrile with morpholine gives a low yield of the 4,6-dimorpholinopyrrolo[2,3-c][1,2,6]selenadiazine-5-carbonitrile (8%) together with 2,5-dimorpholino-3-oxo-3H-pyrrole-4-carbonitrile (13%) and 3,5-dimorpholino-2-oxo-2H-pyrrole-4-carbonitrile (55%).