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2,5,7,9-Tetrathiabicyclo4.3.0)non-1(6)-en-8-thione (3) is prepared in increased yield by isolating the intermediate 4,5-dimercapto-1,3-dithiole-2-thione disodium salt (2) which undergoes efficient ring-closure with 1,2-dibromoethane. Quantitative oxidation of 3 with mercuric acetate to 2,5,7,9-tetrathiabicyclo 4.3.0non-1(6)-en-8-one (4) followed by coupling with triethyl phosphite yields bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF) in high overall yield.
Varma et al. (Thu,) studied this question.