Beta substituted thiols and various derivatives containing the HX–C–C–SH motif oligomerise in water, preferably in the presence of a carbonate salt. The reaction yields oligomers consisting of one thiol end group, a thiaethylene backbone and an additional terminal group corresponding to the starting material used. Mechanistic studies, as well as the scope of substrates and products of these new promising condensation processes, are presented. In addition, strong nucleophiles were also reacted with mercaptoethanol under simple reaction conditions, leading to the selective formation of more complex molecules.