Synthesis of Linear and Angular Triquinane Skeletons by O-Stannyl Ketyl-Promoted Fragmentation−Cyclization Reactions of α-Keto Cyclopropanes

Several investigations of rigid α-keto cyclopropane cleavage by O-stannyl ketyls are summarized herein. Tricyclo[3.3.0.02,8]octan-3-one ring systems were treated with nBu3SnH, 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 initiated to understand what factors bias bond cleavage in a configurationally restricted α-ketocyclopropane via O-stannyl ketyls. A preference for cleavage of the cyclopropane bond with the best orbital overlap with the ketyl radical sp2-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 an angular triquinane skeleton depending on the length and location an alkene tether on the tricyclo[3.3.0.02,8]octan-3-one precursor.