New chemistry of donor-acceptor cyclopropanes
| dc.contributor.advisor | Pagenkopf, Brian L. | en |
| dc.creator | Yu, Ming | en |
| dc.date.accessioned | 2008-08-28T22:01:06Z | en |
| dc.date.available | 2008-08-28T22:01:06Z | en |
| dc.date.issued | 2004 | en |
| dc.description | text | en |
| dc.description.abstract | Donor-Acceptor (DA) cyclopropanes are considered to be well-understood compounds with predictable chemistry. This dissertation focuses on our recent advances and synthetic applications of DA cyclopropanes principally involving 1,3-dipole intermediates revealed by reactions with Lewis acids. Particular emphasis is placed on reactions involving sugar-derived substrates. Chapter one is an overview of the literature preparations and synthetic applications of DA cyclopropanes. It begins with general DA cyclopropanes but is mostly focused on carbohydrate-derived cyclopropanes. Chapter two describes our intramolecular glucal cyclopropanation approach toward lactonized cyclopropanes 2.5a-c, their transformations under mild conditions, and their application to the quasi formal synthesis of the natural product xylobovide 2.34a. Chapter three investigates the different chemical behaviors of glucal-derived lactonized cyclopropane 2.5a under the influence of a variety of different Lewis acids. Use of boron trifluoride etherate (BF3•OEt2) leads to regioselective mono-desilylation of the di-tert-butylsilylene ether to 2.27; trimethylsilyl trifluoromethanesulfonate (TMSOTf) results in anhydro-sugar 3.8 formation; and titanium tetrachloride (TiC4) facilitates stereoselective allylation and glycosidation. Chapter four discuses our recently discovered formal [3+2] dipolar cycloaddition reactions of DA cyclopropanes with a wide variety of dipolarophiles including silyl enol ethers, imines, aldehydes and nitriles. The extension of nitrile cyclization to general noncarbohydrate derived DA cyclopropanes leads to the discovery of a novel synthetic methodology toward pyrroles, bipyrroles and thienylpyrroles. Finally, the [3+2] cycloaddition has also been extended to heterocycles including pyridines, quinolines and indoles. Chapter five summarizes the investigation of regio-selective mono-desilylation of di-tert-butylsilylene ethers as a new protocol for selective hydroxy protection. Under optimized conditions, the reaction demonstrates high regioselectivity as well as strong functional group compatibility, and proves promising as a new protocol for selectively manipulating 1,3-diols. Chapter six provides the experimental procedures and characterization of all the new compounds. | |
| dc.description.department | Chemistry and Biochemistry | en |
| dc.description.department | Chemistry | en |
| dc.format.medium | electronic | en |
| dc.identifier | b59362984 | en |
| dc.identifier.oclc | 58448430 | en |
| dc.identifier.proqst | 3151447 | en |
| dc.identifier.uri | http://hdl.handle.net/2152/1441 | en |
| dc.language.iso | eng | en |
| dc.rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. | en |
| dc.subject.lcsh | Cyclopropane | en |
| dc.title | New chemistry of donor-acceptor cyclopropanes | en |
| dc.type.genre | Thesis | en |
| thesis.degree.department | Chemistry | en |
| thesis.degree.discipline | Chemistry | en |
| thesis.degree.grantor | The University of Texas at Austin | en |
| thesis.degree.level | Doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |