Perthio- and perseleno-1,3-butadienes, -but-1-ene-3-ynes, and -[3]-cumulenes: one-step syntheses from 1,4-dilithio-1,3-butadiyne.

Treatment of 1,4-dilithio-1,3-butadiyne (1) with dichalcogenides RSSR or RSeSeR affords dithio- and diseleno-1,3-butadiynes (2, 3), perthio- and perseleno-[3]-cumulenes (4, 5), perthio- and perseleno-1,3-butadienes (6, 7), and/or perthio- and perseleno-but-1-ene-3-ynes (8, 9). The products can be controlled by stoichiometry and temperature, by the presence or absence of oxygen, and by choice of the "R" group. By X-ray crystallography, hexa(methylthio)-1,3-butadiene is highly twisted, with a torsion angle [(Phi(CCCC) of 84.7degrees and an elongated C(2)-C(3) distance of 1.484(3) Angstrom.