Selective reactions of tertiary carbocations
Citation
Vangal, Prithvi. 2020. Selective reactions of tertiary carbocations. Doctoral dissertation, Harvard University Graduate School of Arts and Sciences.Abstract
Carbocations are fundamental intermediates in organic chemistry. Due to their high reactivity, they participate in a range of reactions enabling the synthesis of a variety of products from a single starting-material. A general catalytic strategy that enables the stereocontrolled addition of nucleophiles to these intermediates would therefore be extremely enabling. Despite the advances in asymmetric catalysis over the past few decades, stereoselective variants of reactions proceeding through tertiary carbocations are underdeveloped. In this work, we describe our efforts toward the development of a general catalytic platform to achieve selectivity in reactions proceeding through these intermediates.In Chapter 1, we describe the successful development of a hydrogen-bond-donor catalyzed, enantioselective synthesis of quaternary stereocenters from tertiary electrophiles. A complete catalytic cycle is established through detailed mechanistic studies. These studies reveal that the reaction proceeds through an SN1-like mechanism involving rate-determining ionization of the electrophile to generate a tertiary carbocation. The mechanism of enantioinduction is determined to be a stereoablative process and the key C–C bond-forming event is found to be the enantiodetermining step.
In Chapter 2, we describe our studies on extending this catalytic platform to reactions involving heteroatomic nucleophiles. Our studies show that, in principle, hydrogen-bond donors can effect the addition of heteroatomic nucleophiles to tertiary carbocations with high stereoselectivity. We also present preliminary results on the development of an efficient synthesis of racemic, hindered ethers using simple catalysts.
Terms of Use
This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAACitable link to this page
https://nrs.harvard.edu/URN-3:HUL.INSTREPOS:37369427
Collections
- FAS Theses and Dissertations [5370]
Contact administrator regarding this item (to report mistakes or request changes)