Synthesis of unsaturated organochalcogen compounds proceeding from dichloroethenes and organyl dichalcogenides

Resumo

Reaction of 1,1- and 1,2-dichloroethenes with Ph₂S₂, Ph₂Se₂, Bn₂S₂, and i-Pr₂S₂ in a system hydrazine hydrate–KOH proceeds as a sequence of successive transformations: dehydrochlorination of initial dichloroethenes to form chloroacetylene, chlorine substitution for the chalcogen-containing nucleophile (ethynylchalcogenides formation), and the addition of the nucleophilic reagent to the triple bond affording 1,2- dichalcogenylethenes. In reactions with PhS^– and PhSe^‒ nucleophiles due to the high rate of all stages 1,2-bis (phenylchalcogenyl)ethenes are obtained having mainly the Z-configuration. In reactions with BnS^‒ and i-PrS^‒ in the IR, NMR and chromato-mass spectra intermediate ethynylchalcogenides were identified, and the final products consisted of a mixture with the prevalence of the Z-isomer.