An alpha,alpha'-dioxothione and its

In the reaction of Ninhydrin (1a)/1,2,3-indantrione (1b) with potassium thiotosylate, 1,4-oxathiin 6 is formed in up to 63% yield as the trapping product of the intermediary alpha,alpha'-dioxothione 1c with trans-cyclooctene (3a). Additionally, up to 18% of the available sulfur is transferred to olefin 3a to thiirane 3b through the intermediary oxathiirane.