Development of Methodology for the Synthesis of Strained Medium- and Small-Sized Rings Using Silylenes as Reactive Intermediates and Investigations into the Mechanisms of Catalyzed and Uncatalyzed Reactions of Silylenes and Silacyclopropanes

The synthesis of strained medium-sized rings with control of the relative stereochemistry is limited due to the inherent difficulty of the synthesis and isolation of these cyclic compounds. A method for the diastereoselective synthesis of eight-membered ring allenes from propargyl epoxides, silylenes, and aldehydes was developed. An analysis of the solid-state structure of these allenes indicates that these compounds are strained compared to their acyclic counterparts. Efforts were made to expand the variety of medium-sized unsaturated rings that could be synthesized using silylene transfer methodology. As a result of these efforts, syntheses of four-membered ring silicon-containing rings were developed using silylenes as reactive intermediates.;Studies were executed to further understand the mechanisms of the reactions of silylenes and silacyclopropanes. Attempts to develop an asymmetric silylene transfer reaction were made by transferring silylenes to chiral enantiopure alkene starting materials. No asymmetric induction was observed for a variety of conditions. This lack of selectivity indicates a steric barrier to successfully incorporating a bulky chiral ligand, a di-tert-butylsilylene group, and an alkene group all in the silylene transfer step. The reactions of silacyclopropanes with benzoquinones and other enones were investigated. Electron-deficient carbonyl compounds were inserted into the carbon--silicon bond of silacyclopropanes to provide oxasilacyclopentane without the aid of a metal catalyst. Mechanistic experiments provided evidence that insertions of carbonyl compounds into the carbon--silicon bond of silacyclopropanes involves radical intermediates depending on the electronic nature of the carbonyl functional group.