Dianions of 3-oxodithioic acids: preparation and conversion to 3H-1,2-dithiole-3-thiones

Reaction of ketones with CS2 and 2 equivalents of KH in THF–N,N′-dimethylpropyleneurea solution produces the dianions of 3-oxodithioic acids. These dianions are converted in good yield to 3H-1,2-dithiole-3-thiones by the sequential action of hexamethyldisilathiane and an oxidizing agent such as hexachloroethane.