Synthesis of linear and angular triquinane skeletons by O-stannyl ketyl-promoted fragmentation-cyclization reactions of alpha-keto cyclopropanes

Several investigations of rigid alpha-keto cyclopropane cleavage by O-stannyl ketyls are summarized herein. Tricyclo[3.3.0.0(2,8)]octan-3-one ring systems were treated with nBu(3)SnH, which produced different ring-cleavage products depending on the location and type of substituent present. An examination of both radical-stabilizing substituents and stereoelectronic factors was initiateci to understand Ft-hat factors bias bond cleavage in a configurationally restricted alpha-ketocyclopropane via O-stannyl ketyls. A preference! for cleavage of the cyclopropane bond with the best orbital overlap with the ketyl radical sp(2)-orbital even in the presence of radical stabilizing groups is indicated by these results. An O-stannyl ketyl ring scission-cyclization resulted in the novel synthesis of either a linear or angular triquinane skeleton depending on the length and location an alkene tether on the tricyclo[3.3.0.0(2,8)]octan-3-one precursor.