Structural models for the study of nucleophile/electrophile interactions and bond formation.

Bristow, J.C., 2020. Structural models for the study of nucleophile/electrophile interactions and bond formation. PhD, Nottingham Trent University.

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Abstract

This thesis is divided into seven chapters. Chapter 1 gives an introduction to intermolecular interactions, the discovery and development of n-π* interactions and explores the use of various aromatic backbones (in particular naphthalene) as the scaffold for generating nucleophile/electrophile interactions.

Chapters 2-7 form the results and discussion of the thesis. Chapter 2 reports the first peri-interactions between naphtholate oxyanions and electrophilic double bonds in the form of tetramethylguanidine crystalline salts with O---C contacts in the range: 2.558(2)–2.618(2) Å.

Chapters 3-7 are concerned with nitrogen---carbon interactions. Chapter 3 explores the widening of an interaction distance between a dimethylamino nucleophile and a range electrophilic groups, via the use of acenaphthene and fluorene scaffolds. The increase in the contact distance between the two groups allows for cyclisation through an N-methyl group via a tert-amino effect reaction in a number of cases. This generates a range of azepine and azocine fused ring systems.

Chapter 4 explores the reduction of an interaction distance between a dimethylamino nucleophile and a range of electrophilic alkenes, via peri-repulsion between groups at the opposite peri-positions. This repulsion in all cases led to a reduction in the N---C distance, resulting in a short contact of 2.359(2) Å in the ethenedinitrile derivative and the formation of a long N-C bond of 1.672(1) Å when one nitrile was replaced by an ester group.

Chapter 5 introduces a symmetrical system with a set of N---C(alkene) peri-interactions at both positions. Generally, the N---C distances increased throughout the series compared to the corresponding systems with just one set of interactions and no second set of peri groups. When the alkene terminated in a cyclic diester (from Meldrum’s acid) a long N-C bond (1.676(4) Å) formed at one peri site and a N---C contact of 2.615(4) Å remained at the other. Further systems demonstrating a peri Me2N+H---H repulsion were also generated, leading to compounds with N-C bonds in the range of 1.7-2.1 Å. Of particular importance is the ethenedintrile derivative, which undergoes a reversible structural change in the solid-state under cooling, which was carefully mapped by X-ray diffraction. Preliminary variable temperature SSNMR and charge density studies on this system are also reported.

Chapter 6 reports the four structures which demonstrate the Felkin-Anh model for nucleophilic attack of a carbon centre adjacent to a chiral centre. Combining the approaches demonstrated in Chapters 2-4.

Chapter 7 reports structures where a dimethylamino group reacted with a range of stabilised carbocation centres across the peri-positions on naphthalene to form long N-C bonds (1.653(2)1.673(2) Å), and in some cases some interesting fused multi-ringed systems were produced.

Item Type: Thesis
Creators: Bristow, J.C.
Date: January 2020
Rights: This work is the intellectual property of the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed in the owner of the Intellectual Property Rights.
Divisions: Schools > School of Science and Technology
Record created by: Jeremy Silvester
Date Added: 05 Aug 2020 13:34
Last Modified: 05 Aug 2020 13:34
URI: http://irep.ntu.ac.uk/id/eprint/40335

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