'Organic metals': Synthesis of dithiolylidenetetrathiapentalenones and their higher analogues

Reaction of the tetrathiapentalene-2,5-dione (1) and 4,5-dimethoxycarbonyl- 1,3-dithiole-2-thione (2) with trimethylphosphite in refluxing benzene provides, along with the expected self-coupled products, the dithiolylidenetetrathiapentalenone (4; R = CO2Me) and its higher analogue (6; R = CO2Me).