Formation of Thiocarbonyl Compounds in the Reaction of Ebselen Oxide with Thiols

Reaction of a-toluenethiol with Ebselen oxide, 2, affords dibenzyl disulfide and seleno sulfide 5, R = PhCH₂. In the course of this reaction, thiobenzaldehyde is formed and can be trapped with cyclopentadiene in 90% yield. Reaction of 2-propene-1-thiol with 2 afforded thioacrolein dimer in 69% yield and seleno sulfide 5, R = CH₂-CH=CH₂. Trapping, stereochemical, and isotopic exchange studies were used to determine if in the reaction of 2 with 1-heptanethiol, cyclohexanethiol, and N-acetyl-D,L-cysteine thiocarbonyl compounds heptanethial, cyclohexanethione, and 2-acetamino-3-thioxopropanoic acid (α-thioformyl-N-acetylglycine), respectively, are also formed. These studies showed that free thiocarbonyl compounds are not formed in these reactions.