자료유형  

 학위논문

Control Number  

0016934087

International Standard Book Number  

9798380318310

Dewey Decimal Classification Number  

547

Main Entry-Personal Name  

Lui, Nathan Mancheun.

Publication, Distribution, etc. (Imprint  

[S.l.] : Cornell University., 2023

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2023

Physical Description  

1 online resource(914 p.)

General Note  

Source: Dissertations Abstracts International, Volume: 85-03, Section: B.

General Note  

Advisor: Collum, David B.

Dissertation Note  

Thesis (Ph.D.)--Cornell University, 2023.

Restrictions on Access Note  

This item must not be sold to any third party vendors.

Summary, Etc.  

요약Camphorsultam-based enolates, referred to colloquially as Oppolzer enolates, are examined spectroscopically, crystallographically, kinetically, and computationally to ascertain the mechanism of alkylation and the origin of stereoselectivity. Solvent- and substrate-dependent structures of lithium Oppolzer enolates include tetramers for alkyl-substituted enolates in toluene, spirocyclic dimers for aryl-substituted enolates in toluene, substrate-independent symmetric dimers in tetrahydrofuran (THF) and THF/toluene mixtures, hexamethylphosphoramide-bridged (HMPA) trisolvated dimers at low HMPA concentrations, and disolvated monomers for the aryl-substituted enolates at elevated HMPA concentrations. Their sodium counterparts, however, reside as monomers in neat THF and THF/HMPA solutions and as dimers in toluene when solvated by N,N,N'N'-tetramethylethylenediamine (TMEDA) and N,N,N',N''N''- pentamethyldiethylenediamine (PMDTA). Aided by density functional theory (DFT) extensive analyses of the stereochemistry of aggregation and solvation are included. Rate studies of allylation implicate analogous transition structures, namely an HMPA-solvated ion pair with a +Li(HMPA)4 or +Na(HMPA)5 counterion. Curious dependencies on toluene and THF are attributed to exclusively secondary-shell (medium) effects. Sparse reports detailing an analogous HMPA-free methylation are also explored, revealing a similar reaction pathway (via the THF-solvated E- //+Na(THF)6 ion pair). Aided by DFT calculations, a stereochemical model is presented in which the alkylating agent is guided to the exo-face of the camphor owing to stereoelectronic preferences imparted by the sultam sulfonyl moiety, rather than chelate directed endo-facial approach. Consequently, counter to decades of reasoning, the origins of stereoselectivity stem not from steric effects enforced by the chelation of the metal cation, but rather from chirality within the sultam ring imparted by the rigidity of the camphor skeletal core.

Subject Added Entry-Topical Term  

Organic chemistry.

Subject Added Entry-Topical Term  

Physical chemistry.

Subject Added Entry-Topical Term  

Computational chemistry.

Index Term-Uncontrolled  

Camphorsultam

Index Term-Uncontrolled  

Enolates

Index Term-Uncontrolled  

Kinetics

Index Term-Uncontrolled  

Mechanism

Index Term-Uncontrolled  

Tetrahydrofuran

Added Entry-Corporate Name  

Cornell University Chemistry and Chemical Biology

Host Item Entry  

Dissertations Abstracts International. 85-03B.

Host Item Entry  

Dissertation Abstract International

Electronic Location and Access  

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Control Number  

joongbu:642367