1.3- Dithiolylium ions reduction

Electrochemical reduction of the 2-ethylthio-l,3-dithiolylium salts (344) in acetonitrile gives the corresponding dimers (345) which can then pyrolyze to the tetrathiafulvalene derivatives (24) in nearly quantitative yields (74JA945). When one considers the total yield, this method is superior to the base-catalyzed dimerization of 1,3-dithiolylium ions. However, for large-scale synthesis, the convenience may be questionable. 

Figure 42. Constant current coulometry (25 mA) of 3,4-diphenyl-1,2-dithiolylium ion (0.1 mmol). Cyclic voltammograms, horizontally displaced, are shown after reduction for 0, 1,2, 3, 4, 5, and 6 min, respectively.

Reaction of the immonium ion (157) with dihydrogen sulfide produces the l,3-dithiole-2-thione (158) while reduction of the ion (157) with sodium borohydride, followed by treatment with sulfuric acid, resulted in the formation of the 1,3-dithiolylium salt (48) (76S489). 

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