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|Title: ||An investigation of the preparation of heterocyclic ring systems via intramolecular nucleophilic aromatic substitutes|
|Authors: ||Smith, Phillip H.G.|
|Issue Date: ||1985|
|Publisher: ||© Phillip Henry Gaunt Smith|
|Abstract: ||Heterocyclic synthesis via processes involving single electron
transfer, namely aromatic SRN1 ,reactions and copper metal- and
cuprous halide-promoted substitutions have been investigated. The
cyclisation step in all the 'syntheses is effected by an intramolecular
aromatic nucelophilic substitution on a halogen atom which is ortho
to the side chain bearing the nucleophilic species (generally an amide
or thioamide moiety). The process of entrainment has been shown to be a valuable technique
for effecting reactions performed' under SRN1 conditions.
The mechanisms of, and the mechanistic relationships between the
substitution processes, were investigated using well documented diagnostic
probes for the SRN1 reaction and by conducting series of experiments
on simple reaction systems whose behaviour under SRN1 conditions was
already known. Ring systems prepared by the methods noted above include benzoxazoles,
benzothiazoles, 1 ,3-benzothiazines, indoles and a tricyclic system.
Attempts to prepare seven-membered heterocycles by increasing the length
of the side chain proved unsuccessful.
When the side chain bears a carbonyl function adjacent to the aromatic
ring, an intramolecular SNAr reaction takes place and cyclisation of
N-(2-haloaroyl)-N'-phenylthioureas occurred under mild conditions.
Quinazolinones and a 1 ,3-benzothiazinone have been synthesised in
this manner which appears to have little precedent in the chemical
literature. The preparation of seven-membered heterocycles by an SNAr cyclisation
proved fruitless extension of the side chain length by one carbon atom
(effected by the preparation of an N-cinnamoyl-N-phenylthiourea)
resulted in the cyclisation of the side chain.
Reaction of certain of the N,N-disubstituted thioureas with copper (1)
iodide results in the formation of 2-halobenzanilides by a novel
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Chemistry)|
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