Dissertation Information for Christopher Sean StraubNAME:
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SCHOOL: ADVISORS: COMMITTEE MEMBERS: MPACT Status: Fully Complete Title: Rhodium-mediated cyclizations of alpha-diazo carbonyl compounds: The use of diazo imides and acetylenic diazo esters for alkaloid synthesis Abstract: "Rhodium(II) catalyzed decomposition of ¦Á-diazo esters containing alkynyl tethers results in the formation of vinyl carbenoids which can be intercepted by adjacent carbonyl groups to produce 2-heteroatom substituted furans. This tandem cyclization/6¦Ð-electrocyclization sequence is dependent on many factors, including the solvent employed, the ligands attached to the rhodium catalyst, the conformational rigidity of the system, and the substituents on the alkynyl tether. When terminal alkynes are used the cyclization does not occur. However, the presence of a trimethylsilyl group at the terminal position facilitates the reaction and permits access to various 2-alkoxy and 2-amino substituted furans. The intermolecular Diels-Alder cycloaddition of these furans was explored. By varying the conditions and the dienophiles used it was possible to produce an array of heterocyclic compounds. Protodesilylation of the silyl substituted furans prior to the Diels-Alder reaction greatly facilitated the cycloaddition. This protocol was also employed for the synthesis of furans containing tethered ¦Ð-bonds. Protodesilylation of these furan systems followed by thermolysis produced novel polycyclic ring systems. Several model systems were examined with the intention of using the methodology towards a planned synthesis of the alkaloid strychnine. |
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