Indirect electrochemical oxidations in organic chemistry
Indirect electrochemical oxidations in organic chemistry
Redox couples have been used as mediators for the anodic oxidation of organic compounds in several media including acetonitrile, methanol and pyridine/HF. Cyclic voltammetric and preparative techniques have been used to study the behaviour of such redox couples in the presence of substrates. Tris(4-bromophenyl)amine has been shown to be an effective electron transfer mediator for the indirect oxidation of amines. Using an undivided cell and a methanol/dichloromethane medium, benzyl amines were converted to the corresponding Schiff bases in excellent yield. With amines where there are hydrogens in the β-carbon, however, no simple products were isolated and it is likely that the imine intermediate polymerises. It was shown that the selectivity as well as the maximum current density for such indirect oxidations depends strongly on the electrolysis conditions. The indirect oxidation of 3-phenoxytoluene mediated by tris(2,3-di-bromophenyl)amine in the presence of chloride ions led to good yields of 3-phenoxy-6-chlorotoluene at reasonable rates. Ring-substitution was also found when the nucleophile was acetate ion or methanol. Pyridine.9HF and triethylamine.3HF were employed as media for indirect oxidations. Oxidation potentials of potential mediators and of substrates in these media were measured by cyclic voltammetry; preparative electrolyses showed that nucleophilic substitution by other species e.g. bromide or chloride could be achieved in these media, but no examples of indirect fluorination were identified.
University of Southampton
1989
Zappi, Guillermo Daniel
(1989)
Indirect electrochemical oxidations in organic chemistry.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Redox couples have been used as mediators for the anodic oxidation of organic compounds in several media including acetonitrile, methanol and pyridine/HF. Cyclic voltammetric and preparative techniques have been used to study the behaviour of such redox couples in the presence of substrates. Tris(4-bromophenyl)amine has been shown to be an effective electron transfer mediator for the indirect oxidation of amines. Using an undivided cell and a methanol/dichloromethane medium, benzyl amines were converted to the corresponding Schiff bases in excellent yield. With amines where there are hydrogens in the β-carbon, however, no simple products were isolated and it is likely that the imine intermediate polymerises. It was shown that the selectivity as well as the maximum current density for such indirect oxidations depends strongly on the electrolysis conditions. The indirect oxidation of 3-phenoxytoluene mediated by tris(2,3-di-bromophenyl)amine in the presence of chloride ions led to good yields of 3-phenoxy-6-chlorotoluene at reasonable rates. Ring-substitution was also found when the nucleophile was acetate ion or methanol. Pyridine.9HF and triethylamine.3HF were employed as media for indirect oxidations. Oxidation potentials of potential mediators and of substrates in these media were measured by cyclic voltammetry; preparative electrolyses showed that nucleophilic substitution by other species e.g. bromide or chloride could be achieved in these media, but no examples of indirect fluorination were identified.
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Published date: 1989
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Local EPrints ID: 461609
URI: http://eprints.soton.ac.uk/id/eprint/461609
PURE UUID: 5ef6aa35-e650-4201-aa85-e8f067126f47
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Date deposited: 04 Jul 2022 18:50
Last modified: 04 Jul 2022 18:50
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Author:
Guillermo Daniel Zappi
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