Synthesis of new tetra- and pentacyclic, methylenedioxy- and ethylenedioxy-substituted derivatives of the dibenzo[ c , f ][1,2]thiazepine ring system

New tetra- and pentacyclic derivatives of the dibenzo[ c , f ][1,2]thiazepine ring system have been synthesized. The target compounds contain methylenedioxy or ethylenedioxy substituents linked to the benzene ring. The key step for the construction of the ring systems has been implemented by an intramolecular Friedel–Crafts cyclization. Altogether eight new ring systems are described here, five of them are also characterized by single-crystal X-ray diffraction.