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Structure-Reactivity Relationships o...

Mack, Kyle Anthony.

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Structure-Reactivity Relationships of Lithium Amides: LiHMDS-Mediated Enolizations of Hindered Aryl Ketones and LiTMP-Mediated Ortholithiations.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Structure-Reactivity Relationships of Lithium Amides: LiHMDS-Mediated Enolizations of Hindered Aryl Ketones and LiTMP-Mediated Ortholithiations./
作者:	Mack, Kyle Anthony.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
面頁冊數:	195 p.
附註:	Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Contained By:	Dissertation Abstracts International79-10B(E).
標題:	Organic chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10744671
ISBN:	9780438025660

Structure-Reactivity Relationships of Lithium Amides: LiHMDS-Mediated Enolizations of Hindered Aryl Ketones and LiTMP-Mediated Ortholithiations.
Mack, Kyle Anthony.

Structure-Reactivity Relationships of Lithium Amides: LiHMDS-Mediated Enolizations of Hindered Aryl Ketones and LiTMP-Mediated Ortholithiations. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 195 p.

Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.

Thesis (Ph.D.)--Cornell University, 2018.

Enolizations of highly substituted acyclic ketones used in the syntheses of tetrasubstituted olefin-based anticancer agents are described. Lithium hexamethyldisilazide (LiHMDS)-mediated enolizations are moderately Z-selective in neat tetrahydrofuran (THF) and E-selective in 2.0 M THF/hexane. The results of NMR spectroscopy show the resulting enolates to be statistically distributed ensembles of E,E-, E,Z-, and Z,Z-enolate dimers with subunits that reflect the selectivities. The results of rate studies trace the preference for E and Z isomers to tetrasolvated- and pentasolvated-monomer-based transition structures, respectively. Enolization using LiHMDS in N,N-dimethylethylamine or triethylamine in toluene affords a 65:1 mixture of LiHMDS?lithium enolate mixed dimers containing E and Z isomers, respectively. Spectroscopic studies show that condition-dependent complexation of ketone to LiHMDS occurs in trialkylamine/toluene. Rate data attribute the high selectivity exclusively to monosolvated-dimer-based transition structures.

ISBN: 9780438025660Subjects--Topical Terms:

523952
Organic chemistry.

Structure-Reactivity Relationships of Lithium Amides: LiHMDS-Mediated Enolizations of Hindered Aryl Ketones and LiTMP-Mediated Ortholithiations.
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300 $a 195 p.
500 $a Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
500 $a Adviser: David B. Collum.
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520 $a Enolizations of highly substituted acyclic ketones used in the syntheses of tetrasubstituted olefin-based anticancer agents are described. Lithium hexamethyldisilazide (LiHMDS)-mediated enolizations are moderately Z-selective in neat tetrahydrofuran (THF) and E-selective in 2.0 M THF/hexane. The results of NMR spectroscopy show the resulting enolates to be statistically distributed ensembles of E,E-, E,Z-, and Z,Z-enolate dimers with subunits that reflect the selectivities. The results of rate studies trace the preference for E and Z isomers to tetrasolvated- and pentasolvated-monomer-based transition structures, respectively. Enolization using LiHMDS in N,N-dimethylethylamine or triethylamine in toluene affords a 65:1 mixture of LiHMDS?lithium enolate mixed dimers containing E and Z isomers, respectively. Spectroscopic studies show that condition-dependent complexation of ketone to LiHMDS occurs in trialkylamine/toluene. Rate data attribute the high selectivity exclusively to monosolvated-dimer-based transition structures.
520 $a Rate and mechanistic studies of ortholithiations by lithium 2,2,6,6-tetramethylpiperidine focus on four arenes: 1,4-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, 1,3-dimethoxybenzene, and 4,4-dimethyl-2-phenyl-2-oxazoline. Metalations occur via substrate-dependent combinations of monosolvated monomer, disolvated monomer, and tetrasolvated dimer (triple ions). Density functional theory computational studies augment the experimental data. We discuss the challenges presented by shifting dimer--monomer proportions in determining the observable reaction orders and our mathematical treatment of such shifting in reactant structure.
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