N,N-dimethylformamide-mediated sodium reduction of trans-3,3'-benzo[c]thienylidene-1,1'-dithione and trans-3,3'-benzo[c]selenonylidene-1,1'-dithione.

[reaction: see text] The synthesis of stable methylthio-capped biisothianaphthene and biisoselenophene derivatives has been achieved using DMF-mediated sodium reduction of cyclic thiocarbonyl compounds.