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Honors Thesis




This thesis describes the investigation of the synthetic utility of dienophiles activated by organometallic alkyne complexes in the Diels-Alder reaction. The principles behind this thesis are staples of the Shea laboratory and have guided many years of research. The objective of this research is to devise novel methodology to quickly and efficiently convert acyclic starting materials into complex polycyclic ones using tandem transition metal-mediated cyclizations. Common themes of this research include cobalt alkyne chemistry and the Diels-Alder, Nicholas and Pauson-Khand reactions. This thesis focuses on establishing a new class of Diels-Alder dienophiles which are activated through the generation of a carbocation stablized by a cobalt alkyne complex. This idea developed from years of research in the Shea laboratory and may be traced back to 2003 when Miriam Quintal synthesized 5-8-5 oxygen-containing tricycle 4 via tandem Nicholas/Pauson-Khand reactions (Scheme 1). One goal of this project was to expand the size of heterocycles synthesized by the Nicholas reaction to include 9- or 10 membered rings. The other was to use tandem Nicholas/Pauson-Khand reactions for the synthesis of tricyclic heterocycles. Miriam showed that compound 2 could be formed from 1 using established chemistry in good yields before conducting a Lewis acid promoted Nicholas reaction to yield heterocycle 3. The Pauson-Khand reaction effectiently converted heterocycle 3 into 5-8-5 tricylcle 4 via standard conditions.




87 leaves : ill. Thesis (Honors)--Smith College, Northampton, Mass., 2008. Includes bibliographical references.