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Aspects of the chemistry of reactive intermediates

Investigations into the role of alkenes as promoters of benzyneformation from N-Nitrosoacetanilide, using furan as a benzyne trap showed that the ability of the alkene to trap and efficiently delocalise free radicals involved in competing processes was of primary importance, while the resistance of the radical-alkene adduct to subsequent oxidation appeared to be an additional controlling factor. Thus good benzyne promotion was observed using dibenzofulvene and 1, 1-(bis-4-biphenylyl)ethene while 1, 1-dibenzoylethene showed no promoting effect. The use of 1,1-diphenylethene as a promoter with ring-substituted N-nitrosoacetanilides showed that while yields of 4-t-butylbenzyne derived from _N-nitroso-4-t-butylacetanilidc were significantly increased with respect to the reaction in the absence of alkene, no significant effects were observed on the yields of arynes derived from N-nitroso-4-methoxyacetanilide and N-nitroso-4-methylacetanilide; the formation of free radical derived products was suppressed in each case. N-Nitroso-2- and 4-chloroacetanilides in benzene and 1,1-diphenylethene underwent substitution of chloride by acetate and formed diazonium chlorides. N-Nitroso-2- and 4-acetoxyacetanilides decomposed via the intermediacy of benzoquinone monodiazides and carbenes as was shown by the isolation of 1,4dioxa-2, 3-benzofulvalene from the decomposition of N-nitroso-2-acetoxyacetanilide in p-xylene. N-Nitroso-2-thioacetoxyacetanilide decomposed in benzene to yield 1, 2, 3-benzothiadiazole. In the reaction of diaroyl peroxides with dimethyl acetylenedicarboxylate (DMAD) to form tetramethyl naphthalen-1, 2, 3, 4-tetracarboxylates low yields were shown, by measurement of carbon dioxide evolution, to be in part due to inefficient decarboxylation of the aroyloxy radicals; aroic acid formation was insignificant. The decomposition of dicinnarnoyl peroxide in DMAD gave no cyclised product while bis-a-methylcinnamoyl peroxide in DMAD gave a low yield of dimethyl 3-methylnaphthalen-1, 2-dicarboxylate.

Identiferoai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641924
Date January 1976
CreatorsBrennan, John
PublisherUniversity of Edinburgh
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Sourcehttp://hdl.handle.net/1842/12736

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