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https://hdl.handle.net/2142/21280
Description
Title
The synthesis and use of cyclic nitronic esters
Author(s)
Kesler, Brenda S.
Issue Date
1993
Doctoral Committee Chair(s)
Denmark, Scott E.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
The Lewis acid promoted (4+2) cycloaddition of nitrostyrenes with various dienophiles was examined and several issues of selectivity were addressed. Anti diastereomers are formed exclusively in high yields in the cycloaddition with cyclic alkenes. Lewis acid complexation was examined by conducting a Hammett study which showed that electron-rich nitrostyrenes cyclize the fastest. It was shown that nitroalkenes can behave as the diene component of the cycloaddition with cyclic dienes due to the effect of the Lewis acid. Finally, the selectivity of the intramolecular cycloaddition is highly dependant upon the position of sp$\sp2$ centers in the tether. If that center is conjugated with the diene, syn diastereomers are afforded exclusively.
The ability to employ chiral Lewis acids was examined in Chapter 3. A suitable Model System was synthesized and a survey of many Lewis acids and ligands provided only low ee's (33%) of products with a titanium trachloride/2,2$\sp\prime$-binaphthol blend.
In efforts to exploit the products obtained from these cycloadditions, we attempted to add tethered carbon radicals to the nitronic ester. Photolysis with hexamethylditin successfully formed the correct carbon-carbon bond, but products were isolated in low yield and in the wrong oxidation state. The slow addition of tributyltin hydride and AIBN afforded high yields of novel N-hydroxy N,O-acetal bicyclic compounds.
Finally, various $\beta$-heteroatom-substituted nitroalkenes were synthesized and successfully underwent cycloaddition with butyl vinyl ether. These nitronic esters were hydrogenated with PtO$\sb2$ to afford 3-substituted pyrrolidines.
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