7-Chloro-2,3-dihydrobenzo(f)-l,4-dithiepin (IV) has been synthesized from 2-(2-chloro-ethylmercapto)-5-chlorobenzyl chloride (I). Attempts to synthesize the higher homologues of IV by this method failed because the required intermediates cleaved at the alkyl–sulphur bond. A reaction product of p-chlorothiophenol, formaldehyde, and hydrogen chloride has been identified as 2,8-dichloro-6H,12H-dibenzo(b,f)-l,5-dithiocin (VI), a tricyclic system with the eight-membered ring containing two sulphur atoms.