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-on e ring systems were treated with nBu(3)SnH, which produced different r ing-cleavage products depending on the location and type of substituen t 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-ketocyclopr opane via O-stannyl ketyls. A preference! for cleavage of the cyclopro pane bond with the best orbital overlap with the ketyl radical sp(2)-o rbital even in the presence of radical stabilizing groups is indicated by these results. An O-stannyl ketyl ring scission-cyclization result ed in the novel synthesis of either a linear or angular triquinane ske leton depending on the length and location an alkene tether on the tri cyclo[3.3.0.0(2,8)]octan-3-one precursor.