4-(2-Hydroxyaryl)-1,2,3-selenadiazoles obtained by the action of selenium(IV) oxide on o-hydroxyacetophenone semicarbazones are readily converted into the corresponding potassium benzofuran-2-selenolates via reaction with potassium carbonate. Oxidation of potassium benzofuran-2-selenolates with iodine gives bis(2-benzofuranyl) diselenides in good yields.
The reaction of selenium dioxide with o-hydroxyacetophenone semicarbazones gives 4-(2-hydroxyaryl)-1,2,3-selenadiazoles which undergo ready decomposition by the action of potassium carbonate to form benzofuran-2-selenolates. The latter can be alkylated with methyl iodide and benzyl chloride and arylated with 2,4-dinitrochlorobenzene. Intermediate formation of 2-(o-hydroxyphenyl)ethyneselenolate during decomposition of 1,2,3-selenadiazoles was proved by the isolation of methyl o-methoxyphenylethynyl selenide when the substrate was treated with potassium carbonate in the presence of methyl iodide.