A powerful method to prepare sulfur-rich macrocycles

Various cyclic polysulfanes (up to a 16-membered ring) have been selectively obtained from the corresponding disubstituted trityl-protected polysulfane benzene derivatives upon treatment with elemental iodine in the presence of silica gel. Depending on the position of the sulfur-rich moieties and the presence of a methylene linker between the benzene ring and sulfur atoms, two types of products containing either one or two benzene subunits have been isolated. The scope of the reaction, its selectivity, and mechanism are discussed.