Thesis advisor: Xiaoxiang Peter Zhang / Thesis advisor: James P. Morken / Diazomalonates have been demonstrated, for the first time, as effective radical precursors for asymmetric radical cyclopropanation of alkenes via Co(II)-based metalloradical catalysis (MRC). With an optimized D2-symmetric chiral amidoporphyrin as the supporting ligand, the Co(II)-based metalloradical system can efficiently activate unsymmetrical methyl phenyl diazomalonate (MPDM) for the asymmetric cyclopropanation of alkenes, enabling stereoselective construction of 1,1-cyclopropanediesters bearing two contiguous chiral centers, including at least one all-carbon quaternary stereogenic center. The Co(II)-catalyzed asymmetric cyclopropanation, which operates at room temperature without slow addition of the diazo compound, is generally applicable to a broad range of olefin substrates and tolerates various functionalities, providing a streamlined synthesis of chiral 1,1-cyclopropanediesters in high yields with high level of control in both diastereoselectivity and enantioselectivity. Mechanistic studies on the cyclopropanation reactions, including the use of (E)- and (Z)-b-deuterostyrenes, support the underlying stepwise radical pathway for the Co(II)-catalyzed cyclopropanation. In addition to functioning as effective 1,3-dipoles for stereospecific formation of five-membered ring structures, the resulting enantioenriched methyl phenyl (E)-1,1-cyclopropanediesters serve as useful building blocks for the synthesis of different 1,1-cyclopropanediesters, 1,1-cyclopropaneestercarboxylic acids and 1,1-cyclopropaneesteramides while maintaining the original stereochemistry. Additionally, the enantioenriched (E)-1,1-cyclopropanediesters can be converted to (Z)-diastereomers without affecting the high enantiopurity. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
| Identifer | oai:union.ndltd.org:BOSTON/oai:dlib.bc.edu:bc-ir_109094 |
| Date | January 2021 |
| Creators | Wang, Jingyi |
| 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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