PHOTOOXIDATION OF 1,5-DITHIACYCLOOCTANE - A NOVEL C-S BOND-CLEAVAGE

Sensitized photooxidation of 1,5-dithiacyclooctane (1,5-DTCO) has been investigated in various solvents. At high conversions, a novel C-S bond cleavage occurs. Significant solvent effects are also observed. At high concentration (0.05-0.1 M) in methanol, more than 90% of the corresponding monosulfoxide and a mixture of cis- and trans-bissulfoxides are produced. In aprotic solvents (benzene, chloroform, acetone, and acetonitrile), novel cleavage products (1,2-dithiolane 1-oxide, 1,2-dithiolane 1,1-dioxide, and acrolein) were obtained in addition to the monosulfoxide and bissulfoxides. The cleavage products derive mostly from reaction of the primary monosulfoxide (1,5-DTCO 1-oxide) with singlet oxygen. Unstable compounds oxidized a to the sulfur atom were detected by NMR spectroscopy and shown to be intermediate in the formation of the cleavage products.