RESUMEN
A metal- and catalyst-free photo-promoted cyclization of properly substituted vinyl selenides was developed using UVA irradiation. A total of eighteen new C3-unsubstituted 2-selanyl benzochalcogenophenes (benzofurans, benzothiophenes and benzoselenophenes) were prepared in 30-86% yield after irradiation with UVA at room temperature. The usefulness of the title compounds was demonstrated in the easy functionalization of the remaining free C-H bond of the benzochalcogenophenes to form new C-Se and C-Br bonds by simple procedures. Furthermore, the reaction can be performed under natural sunlight irradiation and the solvent is easily reused further in several subsequent runs.
Asunto(s)
Benzofuranos , Rayos Ultravioleta , Catálisis , Ciclización , SolventesRESUMEN
Herein we describe the synthesis of organoselanyl and organotellanyl alkynes by the addition of lithium alkynylchalcogenolate (Se and Te) to tosyl solketal, easily obtained from glycerol. The alkynylchalcogenolate anions were generated in situ and added to tosyl solketal in short reaction times, furnishing in all cases the respective products of substitution in good yields. Some of the prepared compounds were deprotected using an acidic resin to afford new water-soluble 3-organotellanylpropane-1,2-diols. The synthetic versatility of the new chalcogenyl alkynes was demonstrated in the iodocyclization of 2,2-dimethyl-1,3-dioxolanylmethyl(2-methoxyphenylethynyl)selane 3f, which afforded 3-iodo-2-(2,2-dimethyl-1,3-dioxolanylmethyl) selenanylbenzo[b]furan in 85% yield, opening a new way to access water-soluble Se-functionalized benzo[b]furanes.