The reaction between thiiranes and singlet oxygen has been investigated. Diphenylthiirane is unreactive, but simple alkyl thiiranes react readily, even at low temperature. The products depend on solvent and substrate concentration. In nonnucleophilic solvents, the primary product is the thiirane oxide. In methanol, the primary products are sulfinic esters at low substrate concentration and thiirane oxide at high concentration. It is suggested that the reaction proceeds via an intermediate, for which we assign a peroxythiirane oxide structure. The structures of potential intermediates have been calculated at the ab initio level using a 3-21 G basis set. The reaction mechanism is discussed on the basis of Frontier Molecular Orbital theory and ab initio calculations.
