"We present a family of anionic Mn(II) reagents supported by trisphenylamido- amlne frameworks that offer guidance with regards to ligand selection for developing C—N bond construction methodologies (extensively used in the synthesis of petrochemicals, household chemicals) through nitrene- transfer chemistry. We subsequently extend the study to include the corresponding Fe(II), Co(II), and Ni(II) reagents, to gain insights in their comparative reactivity/selectivity patterns. Attenuated levels of electrophilicity of anionic complexes proved to be more suitable for discriminating aromatic from aliphatic olefins for aziridination purposes, especially for Mn(II) complexes. However, in the case of Co(II) reagents, we observe that additional stereoelectronic parameters can occasionally override the electron-affinity of the metal nitrene as the sole guiding force, which is established as the dominant factor for Mn(II) complexes. We conclude from experimental and computational investigations that carboradical intermediates are generated by initial rate-determining nitrene-addition to one of the olefinic carbons followed by fast ring closure to form the aziridine, with rates that largely depend on the ligand and metal choice.
This study was extended to start exploring intermolecular aziridinations of alkenes catalyzed by metal reagents (Cu, Ag) supported by the rigid cyclic guanidinyl arms possessing chiral elements. In this study, we synthesized a series of cyclic chiral guanidinyl precursors and corresponding metal regents which proved to have good reactivity, but still modest enantioselectivities, in the aziridination of styrenes"--Abstract, page iv.
Mormile, Melanie R.
Ph. D. in Chemistry
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Comparative nitrene-transfer chemistry to olefinic substrates mediated by a library of anionic Mn(II) triphenylamido-amine reagents and m(ii) congeners (M = Fe, Co, Ni) favoring aromatic over aliphatic alkenes
- Is the electrophilicity of the metal nitrene the sole predictor of metal-mediated nitrene transfer to olefins? Secondary contributing factors as revealed by a library of high-spin Co(II) reagents
- Studies directed towards the intermolecular aziridination of alkenes catalyzed by metal reagents (Cu, Ag) supported by bulky ligands with a chiral framework
xviii, 358 pages
© 2021 Anshika Kalra, All rights reserved.
Dissertation - Open Access
Kalra, Anshika, "Development of tripodal and bipodal ligand frameworks and first-row transition metal reagents for selective C-N bond construction methodologies" (2021). Doctoral Dissertations. 3006.