Approaches to the study of the geometry and mechanisms of nucleophilic substitution at oxygen, sulfur (II), and chlorine: Applications of the endocyclic restriction test
Lucas, Douglas Marshall
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https://hdl.handle.net/2142/23066
Description
Title
Approaches to the study of the geometry and mechanisms of nucleophilic substitution at oxygen, sulfur (II), and chlorine: Applications of the endocyclic restriction test
Author(s)
Lucas, Douglas Marshall
Issue Date
1995
Doctoral Committee Chair(s)
Beak, Peter
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
Approaches toward studying the geometry of nucleophilic substitution at oxygen, sulfur (II), and chlorine have been investigated. The endocyclic restriction test has been applied with both double-labeling studies and $\sp1$H NMR Spin Saturation Transfer techniques utilized as methods of analysis.
An oxygen-18 labeling experiment has been used to address the geometrical limitations and requirements in the transition state for olefin epoxidation by sulfonyl oxaziridines. Mass spectral analysis of the distribution of labels in the double-labeling experiment for the conversion of 106 to 107 was consistent with an intramolecular oxygen atom transfer. This indicates that the oxygen atom transfer does not require the olefin to approach the oxaziridine at a large angle relative to the O-N bond in the transition state.
One dimensional $\sp1$H NMR spin saturation transfer techniques have been utilized to study the rate of sulfenyl group transfer in 134-${\bf d\sb4}$. The apparent lack of concentration effects in Cl$\sb2$CDCDCl$\sb2$ suggest that the transfer may have proceeded intramolecularly through a six-membered endocyclic transition state. However, the disappearance of the diamine 133 in an intermolecular control crossover experiment with the disulfenamide 135 without any effect on 135 raises doubt concerning the interpretation of the results from the spin saturation transfer experiments. An approach which would test the geometrical requirements for scrambling of the sulfenyl moiety between nitrogen atoms tethered together without the necessity of using spin saturation transfer analysis has been initiated and described.
Double-labeling analysis incorporating $\sp{37}$Cl has been utilized to study the geometry of substitution at chlorine. Crossover experiments between 144 and 144-${\bf d}\sb{\bf 3},\sp{\bf 37}{\bf Cl}$ indicated that either the transfer occurred intermolecularly to give the substituted chloro-aromatics 145 or that chlorine scrambling of either the starting materials or products had occurred. Control experiments ruled out the possibility of scrambling occurring in the products. However, crossover experiments between 147 and 147-${\bf d}\sb{\bf 3},\sp{\bf 37}{\bf Cl}$ indicate that scrambling between the starting materials may have occurred. Thus, no conclusions were drawn from this work.
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