Serendipitous discovery of new pentacycloundecane molecules

Abstract This study explored the rearrangement process which occurred during Grignard reactions of the pentacycloundecane (PCU) dione, 1. This compound was reacted with vinyl and allyl magnesium bromide to afford PCU-vinyl cyclic ether, 2, and PCU-allyl cyclic ether, 4, which upon ozonolysis afforded compounds PCU dilactone, 3 and PCU-cyclic ether monoacid, 5 respectively. This resulted in the discovery of three novel cage compounds, 2, 4 and 5. The Baeyer-Villiger oxidation of 1 was proposed and investigated experimentally as an alternative synthetic route for the PCU dilactone. The unsymmetrical nature of compounds 2, 4 and 5 resulted in overlapping signals of the methine protons and carbons observed in the 1H and 13C NMR spectra, however, the complexity of the spectra was resolved by using 2D NMR techniques to successfully elucidate these compounds. Herein, the three novel cage compounds including compound 3 were fully characterized by IR and NMR spectroscopy, HRMS. Single crystal X-ray crystallography analysis was also performed on compounds 3 and 5.