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Title: Heteroindoxyls
Author: Gaywood, Alexander P.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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Indoxyl has been synthesised by flash vacuum pyrolysis (FVP) at 650°C of o-azidoacetophenone. At lower pyrolysis temperatures, 3-methylbenz[c]isoxazole was generated. Neighbouring group participation had only a minor effect on the generation of the intermediate nitrene, and electron donating groups para to the azide group had little or no effect on the cyclisation reactions. The reactivity of indoxyl was investigated. For example, an N-substituted product was formed on treatment of indoxyl with methoxymethylene Meldrum’s acid. FVP of this material gave 1-hydroxy-3a-aza-cyclopenta[a]indene-8-one which was shown to exist exclusively as the 1-hydroxy tautomer. On the other hand, reaction of indoxyl with N, N-dimethylformamide diethyl acetal followed by Meldrum’s acid gave a 2-substittued product which gave 5H-pyrano[3,2-b]indol-2-one upon FVP at 650°C. Reaction of indoxyl with DMAD similarly took place at the 2-position. Treatment of 3-acetyl-2-chloropyridine with sodium azide gave 4-acetyltetrazolo[2,5-a]pyridine. This underwent FVP to produce 3-methylisoxazolo[3,4-b]pyridine at 400°C whereas pyrolysis at 680°C allowed the ‘heteroindoxyl’ 1,2-dihydropyrrolo[2,3-b]pyridine-3-one to be isolated for the first time. Many of the reactions carried out on indoxyl could be successfully transferred to this new heteroindoxyl, although the basic nitrogen atom of the pyridine ring produced complications in some examples. FVP of 2-acetyl-3-azidothiophene at 350°C gave 3-methylthieno[3,2-c]isoxazole and the new heteroindoxyl 4,5-dihydrothieno 4,5-dihydrothieno[3,2-b]pyrrol-6-one at 550°C by a similar mechanism to those described above. The reactivity of this compound proved to be broadly similar to that of indoxyl. 2-Acetyl-3-azidobenzo[b]thiophene was synthesised by diazotisation of 2-acetyl-3-aminobenzo[b]thiophene followed by reaction with sodium azide in phosphoric acid. The azido-compound underwent FVP at 300°C to yield 3-methylbenzo[b]thiophene[3,2-c]isoxazole.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available