Selenium-containing heterocycles from isoselenocyanates:: Synthesis of 1H-5-selena-1,3,6-triazaaceanthryiene derivatives

The reaction of aryl isoselenocyanates 8 with methyl 3-amino-4-chloro-1-ethylpyrrolo[3.2-c]quinoline-2-carboxylate (6) in boiling pyridine leads to tetracyclic selenaheterocycles of type 9 in high yield (Scheme 3). A reaction mechanism via an intermediate selenoureido derivative A and cyclization via nucleophilic substitution of Cl by Se is proposed (Schemes 3 and 5). The reaction of 6 with 4-bromophenyl isothiocyanate yields the analogous thiaheterocycle 12 (Scheme 4). The molecular structures of 9c and 12 have been established by X-ray crystallography.