Synthesis and properties of the inner salt, 3,3-dipiperidino-3-propylium-1-dithioate: Adduct of 1,1-dipiperidinoethene and carbon disulfide

The nucleophilic addition of 1,1-dipiperidinoethene to carbon disulfide gives an inner salt, 3,3-dipiperidino-3-propylium-1-dithioate (8), in good yield. The inner salt 8 exists as an equilibrium mixture with its tautomer 3,3-dipiperidinodithioacrylic acid in the ratio of 9:1 in CDCl3 at 22 degrees C. The air-oxidation of 8 leads to bis(3,3-dipiperidinothioacryloyl) disulfide. The inner salt 8, prepared in situ, reacts with a wide variety of alkyl halides to provide a convenient synthesis of alkyl 3,3-dipiperidinodithioaclylates in one-pot.