1,3,5,2,4-Trithiadiazines, previously formed from tetrasulphur tetranitride and diazoalkanes, are syn-thesised from 1,1-bis-sulphenyl chlorides (1; R = H, Cl), (5), (11) and bis(trimethylsilyl)sulphurdiimide (2), and this reaction extends to trithiadiazines with functional groups on carbon. Bissulphenyl chlorides (5a–d) are formed in one step from malonic esters and amides and sulphur dichloride. Pentathiepane (lenthionine)(14), prepared from di-iodomethane and disodium di-sulphide, gives methanebis(sulphenyl chloride) on chlorinolysis and hence, with (2), the parent trithiadiazine (3; R = H). Similarly the pentathiepane (16) is converted into bis-sulphenyl chloride (11) and the spirotrithiadiazine (12). The sensitivity of the heterocyclic ring towards strongly polar reagents precluded the generation of the trithiadiazine cation (17) and anion (19), but the radical (18) is formed on treatment with benzoyl peroxide and benzoyl t-butyl nitroxide (22), resulting in the benzoyloxy and amino-oxy derivatives (21) and (24). m-Chloroperbenzoic acid or nitrogen tetroxide convert trithiadiazine into the S-oxide (25).