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SET‐Mechanismus bei Substitutionsreaktionen an Diorganyldichalkogeniden

1989; Wiley; Volume: 122; Issue: 12 Linguagem: Inglês

10.1002/cber.19891221213

0009-2940

Benno Bildstein, Karlheinz Giselbrecht, Fritz Sladky,

Organic Chemistry Cycloaddition Reactions

SET Mechanism in Substitution Reactions with Diorganyl Dichalcogenides Reaction of the sterically demanding tris(trimethylsilyl)methyl carbanion (Tsi ⊖ ) with bis[tris(trimethylsilyl)methyl] diselenide (Tsi 2 Se 2 ) or ditelluride (Tsi 2 Te 2 ) in THF does not lead to the expected substitution products Tsi 2 Se or Tsi 2 Te. Instead, 2‐ tetrahydrofuranyl tris(trimethylsilyl)methyl selenide ( 4a ) or telluride ( 4b ), tris(trimethylsilyl)methane ( 5 ), and tris(trimethylsilyl)‐methylselenol ( 6a ) are formed. This is interpreted in terms of a single electron transfer (SET) from Tsi ⊖ to the respective diorganyl dichalcogenide, giving rise to intermediate chalcogenyl radicals TsiSe ⊙ and TsiTe ⊙ , which are trapped by the solvent THF. Methyl‐ or phenyllithium react with Tsi 2 Se 2 or Tsi 2 Te 2 to afford the expected substitution products MeChTsi ( 1a , 1b ) or PhChTsi ( 2a , 2b ) ( a : CH  Se, b : Ch  Te), but Products derived from chalcogenyl radicals are detectable in minor yields.