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Title: The synthesis and reactions of alkenyl isoxazoles and isoxazolines
Author: Tout, Jaki
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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Four vinyl-isoxazoles and -2-isoxazolines have been synthesised as potential monomers for polymerisation studies. 5-Phenyl-3-vinylisoxazole was prepared in 38% overall yield by a sequence involving cycloaddition of ethoxycarbonyl-formonitrile oxide to phenylacetylene and then reduction of the resulting 3-carbethoxyisoxazole to the aldehyde using di-isobutylaluminium hydride. In the final stage Wittig olefination of the formyl-isoxazole afforded the target compound. 5-Phenyl-3-vinylisoxazole (17%) and 5-phenyl-3-vinyl-2-isoxazoline (26%) were synthesised similarily from ethyl propiolate & benzohydroximoyl chloride, and styrene & ethyl chlorooximidoacetate, respectively. 3-Phenyl-5-vinyl-2-isoxazoline (84%) was obtained in one step by cycloaddition of benzonitrile oxide to butadiene. An alternative and more direct approach to 3-vinylisoxazolines has been developed based on the cycloaddition reactions of acrylonitrile oxide (ANO), and α,β-unsaturated nitrile oxide. ANO was generated, under modified Mukaiyama conditions, by the dehydration of 1-nitropropene with phenyl isocyanate in the presence of catalytic quantities of triethylamine. ANO was trapped by a variety of olefinic dipolarophiles as its 1,3-dipolar cycloadducts in yields ranging from 17% to 71%. Under similar conditions phenylacetylene reacted in low yield (12%). The series of α,β-unsaturated nitrile oxides was extended to include methacrylonitrile oxide and but-2-enonitrile oxide. The dipolarophilic reactivity series was determined by competition experiments. Six dipolarophiles were investigated: Styrene, α-methylstyrene, methyl acrylate, methyl vinyl ketone and three substituted styrences (p-OMe, p-CI and m-NO2). 13C and 1H NMR spectroscopy were used to identify the products and determine the adduct ratio. The results indicated methyl acrylate to be the most reactive dipolarophile. The 1,1-disubstitution in α-methylstyrene effectively lowered its reactivity due to steric effects.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available