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

Patel, Bhaven (2009). Peri-substituted dithianaphthalenes as sources of reactive intermediates in organic chemistry. University of Birmingham. Ph.D.

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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:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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