Liquid-phase thermal condensation of aromatic and heteroaromatic thiols with β-chloro and β-bromostyrene

Aromatic thiols and 2-thiophenethiol react with β-chloro- and β-bromostyrene when heated to form the corresponding 1-phenyl-2-aryl(thienyl)thioethenes. The reaction begins at 800C and takes place effectively and strictly stereospecifically at 140-1600C. The yield of the respective vinyl sulfides amounts to 70-95%. β-Bromostyrene reacts with thiophenol more slowly than β-chlorostyrene, and this is due to the inhibiting action of the hydrogen bromide, which acts as a trap for the thiyl radicals and gives rise to decomposition of the obtained 1-phenyl-2-phenylthioethene. Among the investigated thiols 2-thiophenethiol has the lowest reactivity