A facile synthesis of bis(ethylenedithio)tetrathiafulvalene and related donors for synthetic metals

Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF; 4a) and related TTF-based donor molecules (4b-d) were prepared in two steps from thiapendione (1). Basic cleavage of 1 yielded the intermediate 4,5-dimercapto-1,3-dithiol-2-one (2) which provided upon alkylation the corresponding 4,5-alkylenedithio-1,3-dithiol-2-ones (3a-d). Coupling of 3a-d in triethyl phosphite furnished the target molecules: BEDT-TTF, bis(propylenedithio)tetrathiafulvalene (BPDT-TTF; 4b), bis[oxybis(methylenethio)]tetrathiafulvalene (BOBMT-TTF; 4c), and bis[thiobis(methylenethio)]tetrathiafulvalene (BTBMT-TTF; 4d). The electrochemical properties of these compounds are briefly discussed. BOBMT-TTF forms a highly conducting charge transfer complex with TCNQ[conductivity(298 K) = 10 S/cm; compaction sample].