New chalcogen-nitrogen π-heterocycles covering 3,1,2,4-benzothiaselenadiazines, 1,3,2,4-benzodithiadiazines and 1,2,4,3,5-benzotrithiadiazepines were synthesized by electrophilic cyclization of compounds Ar–N=S=N–SiMe3 under the action of SeCl2, SeCl4/FeCp2, SCl2 and S2Cl2. Heterocycles obtained were thermolyzed into...