Triethylborane-Induced Radical Cyclization of 1-Allyloxy-2- halosilacyclopentane. Stereoselective Synthesis of 1,3,6-Triols Starting from Silacyclobutane.

1-Allyloxy-2-bromo-1-phenylsilacyclopentane was synthesized by a ring-enlargement reaction of 1-allyloxy-1-phenylsilacyclobutane with LiCHBr2. The treatment of 1-allyloxy-2-bromo-1-phenylsilacyclopentane with n-Bu3SnH in the presence of a catalytic amount of Et3B provided 2-oxa-1-silabicyclo[3.3.0]octane, which was converted into 1,3,6-triol by an oxidative cleavage of silicon–carbon bonds with H2O2. An intermolecular radical addition of 2-iodosilacyclopentane to acetylenic compounds afforded the corresponding iodoalkenes.