Neighboring Group Participation in the Sulfur Atoms and Formation of Dithiodications

Abstract

Monosulfoxide of 1, 5-dithiacyclooctane was dissolved in conc. H₄SO₄ to be converted to the 1, 5-dithiodication ( 1 ) which was idntified by ¹H- and ¹³C-NMR. The dication ( 1 ) was isolated as a hygroscopic powder-like salt by quenching the H₂SO₄ solution with anhydrous ether. The dication ( 1 ) was further converted to the corresponding trifluoromethanesulfonates as a stable crystalline compound. Similarly, other monosulfoxides of various cyclic and acyclic 1, n-dithia derivatives were treated in conc. H₂SO₄ to give 1, n-dithiodications. These monosulfoxides underwent the Pummerer rearrangement upon treatm ent with Ac₂O giving both α- and ω-acetoxy-1, n-dithioethers. Formation of 1, n-dithiodications was also observed during the reactions.
New metacyclophanes(2, 11-dithia[3.3]metacyclophane) bearing a bridged sulfur atom between 9 and 18 positions in the rings were prepared. Both monosulfoxides or the cyclophane itself' gave a new trithiodication where the charges are delocalized among three sul fur atoms with the central one taking a hypervalent structure.