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Peri-substituted dithianaphthalenes as sources of reactive intermediates in organic chemistry

Patel, Bhaven (2009)
Ph.D. thesis, University of Birmingham.

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Abstract

This thesis reports the application of 1,8 dithianaphthalenes (peri-substituted dithianaphthalenes) as sources of, and as a means of stabilising, reactive intermediates in organic chemistry. Three peri-substituted trisulfide-2-oxides (49, 58 and 103) were prepared by reacting 1,8-naphthalene dithiols with thionyl chloride in the presence of pyridine. The trisulfide-2-oxides 49, 58 and 103 were shown to act as sulfur monoxide transfer reagents with dienes. ortho-Substituents on the naphthalene ring increased the rate and lowered the temperature at which SO transfer occurred. Treatment of the resulting sulfoxides under Pummerer conditions afforded the corresponding thiophenes. SO transfer was applied in a formal synthesis of Plavix® and the naturally occurring thioperillene. Mechanistic studies on the SO transfer reaction indicated that the rate-determining step was independent of the diene, and first-order with respect to trisulfide-2-oxide. C-H abstraction from cycloheptatriene suggested formation of triplet SO. vic-Disulfoxides are reactive intermediates in the oxidation of thiosulfinates to thiosulfonates. The oxidation of 1,8-naphthalene disulfides was investigated. Cyclic voltammetry demonstrated that electron-rich 3,8-dimethoxynaphtho[1,8-cd][1,2]dithiole (87) was easier to oxidise than the parent naphthalene disulfide 50. Treatment of 87 with one equiv. of oxidant resulted in formation of thiosulfonate 206 and disulfide 87, suggesting disproportionation of thiosulfinate 205. Oxidation of t-Bu-substituted disulfide, 3,8-di-tert-butylnaphtho[1,8-cd][1,2]dithiole (65), afforded the isolable trans vic-disulfoxide 217. Isomerisation of 217 occurred thermally and photochemically, generating cis vic-disulfoxide 225 and thiosulfonate 224. Complete rearrangement of 217 to the thiosulfonate 224 occurred in refluxing mesitylene, establishing trans-217 as the most stable vic-disulfoxide to date. Bis(sulfonyl)hydroxylamine 284 is proposed as a potential source of nitric oxide (NO) or nitroxy (HNO). 284 was prepared by formal N-insertion into the S(O)-S(O)\(_2\) bond of sulfinyl sulfone 228, prepared in turn through oxidation of disulfide 50. Bis(sulfonyl)hydroxylamine 284 was found to be stable both thermally and photochemically. Investigations into the oxidation of t-Bu-substituted disulfide resulted in the isolation of sulfinic anhydride, 295, from disulfide 65. Desulfonylation occurred when 295 was heated in H\(_2\)O/1,4-dioxane. Deuterium incorporation occurred on running the reaction in D\(_2\)O/1,4-dioxane. Refluxing 295 in PhCl resulted in deoxygenation to disulfide 65.

Type of Work:Ph.D. thesis.
Supervisor(s):Grainger, Richard S.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Subjects:QD Chemistry
Institution:University of Birmingham
ID Code:459
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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