Thesis advisor: Xiao-Xiang Zhang / Thesis advisor: James Morken / This dissertation will present three projects focusing on the development of stereoselective radical cascade reactions via metalloradical catalysis (MRC) using Co(II) D2-symmetric chiral amidoporphyrins [Co(D2-Por*)] as the catalyst. The first project demonstrated the feasibility of applying MRC for asymmetric radical cascade processes by achieving an enantioselective radical bicyclization of 1,6-enynes with diazo compounds, which constructed multi-substituted cyclopropane-fused tetrahydrofurans bearing three contiguous stereogenic centers and one trisubstituted alkene. Detailed mechanistic studies including EPR studies and DFT calculation unveiled a radical-based stepwise mechanism. The synthetic utility of this reaction was demonstrated by a series of diastereoselective transformations of the bicyclic products. In the second project, this strategy was expanded to the application of Co(II)-based MRC to catalyze radical cascade reactions involving hydrogen-atom abstraction (HAA) process. A broad array of homopropargyl ethers reacted with diazo compounds to generate enantiomerically enriched ɑ,β-disubstituted tetrahydrofurans in good yields with high diastereoselectivities and enantioselectivities. The third project explored the utilization of the established strategy to accomplish more challenging bicyclization of 1,6,8-dienynes for the construction of cycloheptadiene-fused tetrahydrofurans in regio- and diastereoselective fashions. Such 5,7-fused ring system has been widely found in natural products and bioactive species. / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
| Identifer | oai:union.ndltd.org:BOSTON/oai:dlib.bc.edu:bc-ir_109379 |
| Date | January 2022 |
| Creators | Zhang, Congzhe |
| Publisher | Boston College |
| Source Sets | Boston College |
| Language | English |
| Detected Language | English |
| Type | Text, thesis |
| Format | electronic, application/pdf |
| Rights | Copyright is held by the author, with all rights reserved, unless otherwise noted. |
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