Organic heterocyclothiazenes. Part 3. Synthesis and structure of 1,3,5,2,4-trithiadiazepines

1,3λ4δ2,5,2,4-Trithiadiazepine (10) has been prepared from 1-chloroethane–1,2-bis(sulphenyl chloride)(11) and bis(trimethylsilyl)sulphurdi-imide (3) and also by dehydrogenation of the 6,7-dihydro derivative (9). Trithiadiazepine (10) is a planar, delocalised, stable 10π aromatic system. Its benzo derivative (4), an analogous 14π aromatic system, has been prepared from benzene–1,2-bis(sulphenyl chloride)(2) and sulphurdi-imide (3). In 6,7-dihydro-1,3λ4δ2,5,2,4-trithiadiazepine (9), similarly prepared from ethane–1,2-bis(sulphenyl chloride)(8) and sulphurdi-imide (3), the five heteroatoms are accurately co-planar, with the out of plane methylene protons rapidly interconverting at room temperature. Reaction of S4N4 with di-t-butyl acetylenedicarboxylate in boiling toluene gave di-t-butyl 1,3λ4δ2,5,2,4-trithiadiazepine-6,7-dicarboxylate (14) and t-butyl 1,3λ4δ2,5,2,4,6-trithiatiazepine-7-carboxylate (15) in low yield.