Dissertation Information for Qui WangNAME:
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SCHOOL: ADVISORS: COMMITTEE MEMBERS: MPACT Status: Fully Complete Title: Cycloaddition of 2-imidofurans and sulfilimines for alkaloid synthesis Abstract: Two major themes are the subject of this thesis. In the first part, 2-substituted imidofurans containing a tethered ð-bond were found to undergo an intramolecular Diels-Alder reaction under very mild conditions to afford oxabridged products with high diastereoselectivity. Several methods were investigated to promote the cleavage of the oxa-bicyclic bridge in the resulting cycloadducts. The reactions studied involved a thermal rearrangement, a rhodium-catalyzed and a SnCl 2 -induced ring opening which afforded highly functionalized hydroindole derivatives. As an extension of our model studies, the IMDAF reaction of 2-imidofurans and the subsequent ring opening chemistry were applied to the synthesis of several alkaloids, including epi -zephyranthine, erysotramidine and 3-demethoxyerythratidinone. In the second part of this thesis, a new and efficient method for the synthesis of highly functionalized ã-lactams was developed based on the reaction of vinyl sulfilimines and dichloroketene.In this process, the reaction of a vinyl substituted sulfilimine with the highly electrophilic dichloroketene first generates a zwitterionic intermediate and this is followed by a [3,3]-sigmatropic rearrangement. Finally, the intramolecular trapping of the Pummerer cation by the amido anion furnishes the observed ã-lactam products. The resulting functionalized lactams are easily converted to a variety of nitrogen containing substrates. This sulfilimine cyclization method was applied to the total synthesis of (±)-desoxyeseroline. In addition, the sulfilimines were also found to undergo a regioselective nucleophilic substitution reaction. In a related study using the tandem Pummerer reaction, a formal synthesis of (±)-deethylibophyllidene was achieved by the application of a Pummerer/Mannich cyclization cascade sequence as the key synthetic strategy. |
MPACT Scores for Qui WangA = 0 Advisors and Advisees Graph |