Synthesis, structure, and oxidation of 3,4‐dihydro‐1,2,5‐benzotrithiepins

Abstract

AbstractStable benzene‐fused polysulfide compounds, 3,4‐dihydro‐1,2,5‐benzotrithiepins (1a‐c), have been prepared, and the structure of 1a has been determined by X‐ray crystallographic analysis. While the electrophilic oxidation of compounds 1 with m‐chloroperbenzoic acid gave the corresponding 3,4‐dihydro‐1,2,5‐benzotrithiepin 5‐oxides (2) in moderate yields, the oxidation of 1 with N‐bromosuccinimide afforded a mixture of 5‐oxides 2, unexpected, inseparable 3,4‐dihydro‐1,2,5‐benzotrithiepin 2,2‐dioxides (3), and 3,4‐dihydro‐1,2,5‐benzotrithiepin 1,1‐dioxides (4). Semiempirical PM3 calculations were carried out, and the computed HOMO of 1a suggested a significant favoring of electrophilic reactions at the sulfur atom at the 5‐position. The treatment of 5‐oxides 2 with acetyl bromide or oxalyl dibromide as halogenating reagents gave 2,2‐dioxides 3 and 1,1‐dioxides 4, suggesting that an intramolecular halogen transfer from the 5‐position (sulfide moiety) to the 1‐ and 2‐positions (disulfide moiety) took place in the reactions.