Tris(trimethylsilyl)silyl Radical Induced Bicyclization of 1,6-Dienes and 1,6-Enynes Providing 3,3-Bis(trimethylsilyl)-3-silabicyclo[3.3.0]octanes and 3-Silabicyclo[3.3.0]oct-1-enes

Treatment of 1,6-dienes with tris(trimethylsilyl)silane in the presence of Et3B or α,α′-azobis(isobutyronitrile) afforded 3,3-bis(trimethylsilyl)-3-silabicyclo[3.3.0]octanes in addition to monocyclized cyclopentanes. Bicyclization of 1,6-enynes provided the corresponding 3-silabicyclo[3.3.0]oct-1-enes.