Silacyclopropanes-Building Blocks for Organic Synthesis

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Despite numerous applications of three-membered ring compounds in stereoselective organic synthesis, silacyclopropanes were not considered as synthetic intermediates. In the previous funding period, we developed several carbon-carbon bond forming reactions of silacyclopropane, and demonstrated that they were stereospecific, stereoselective, and regioselective. We also developed conditions for conversion of the carbon-silicon bonds of the products into carbon-oxygen bonds so that silacyclopropanes would be synthetically useful intermediates. This proposal extends our studies of silacyclopropane chemistry to address fundamental issues including the development of improved methods for silacyclopropanation, the synthesis of highly functionalized and enantiomerically pure silacyclopropanes, and the preparation of silacyclopropanes with structures that are significantly different from those studied to date. Preliminary experiments from our laboratory have already hinted at solutions to these issues. We have shown that silacyclopropanation occurs under thermal conditions without the need for highly reactive reagents. This reaction allows for the preparation of silacyclopropanes in functionalized systems, and it can also be employed to make silacyclopropanes in homochiral form. During the funding period, we will address the following important issues in silacyclopropane chemistry: (1) We will pursue the synthesis of stereochemically homogeneous, functionalized silacyclopropanes. (2) We will develop intramolecular silacyclopropanation processes and study the unique reactivities of the products. (3) We will optimize methods for the synthesis of silacyclopropanes under mild conditions, which will necessitate devising structurally new silacyclopropanes. (4) We will develop new reactions of silacyclopropanes, including catalytic, enantioselective reactions.