Synthesis and reactions of some spiroheterocyclic compounds

Hadji-Pavlidis, V, 1985. Synthesis and reactions of some spiroheterocyclic compounds. PhD, Nottingham Trent University.

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Abstract

The object of this investigation was to synthesise 5- and 6- membered spiroheterocyclic derivatives of p-benzoquinone and of cyclohexa-1, 4- dione-2-ene. An earlier study on the use of secondary aromatic sulphonamides as 'phenol equivalents' in oxidative coupling reactions leading to nitrogen- and oxygen containing spirodienones has been corroborated and extended. Electron withdrawing substituents on the same benzene ring as the secondary sulphonamide gave lower yields of spirodienones, perhaps by reducing the nucleophilicity of the sulphonamide. Efficient routes to 2'-sulphonamido-4-hydroxy or 3, 4, 5- trimethoxy benzophenones were developed; these compounds on anodic or chemical oxidation failed to give spirocyclic products.

The reactions of lithium 2-lithiofuran-3-carboxylate with a number of aryl aldehydes and ketones gave excellent yields of secondary alcohols, which on oxidation gave the corresponding 2-aroylfuran-3-carboxylic acids. Spectroscopic evidence suggested that these keto-acids unexpectedly existed exclusively in lactol forms, which were not suitable for oxidation to spirodienones. However, two of the alcohols were converted to diaryl methanes; on oxidation with lead tetraacetate these gave novel six-membered spirolactones.

Non-oxidative approaches to spirocyclohexadienones involving the construction of a spiro ring on a six-membered ring already at the quinone level of oxidation were next studied. Quinone monoketals reacted with lithium 2-lithiofuran-3-carboxylate in the presence of an equimolar amount of benzoyl chloride to give moderate yields of 5-membered spirolactone cyclohexadiene monoketals. 1, 2-Addition reactions on the less hindered carbonyl group of 2,6-disubstituted-l,4- benzoquinones with lithiated oxazolines gave excellent yields of secondary alcohols, which were converted to 5-membered spirolactones on acid hydrolysis. In one case, however, the product appeared to be a -lactone obtained via dienone-phenol rearrangement of the intermediate -lactone. Attempts to isolate quinone methide monoketals from treatment of p-quinol benzoates with base or by Wittig reactions on quinone monoketals failed to give the desired products.

It seemed that spirocyclic cyclohexenones might be prepared by dehydrogenation of corresponding cyclohexanones. The readily accessible tetramethylene and 2, 2-dimethylpropylene monoketals of 1,4-cyclo- hexanedione by careful control of reaction conditions were converted on treatment with organomagnesium or lithium compounds to spirolactones. Neither these nor the original monoketals could be dehydrogenated.

Quinone monoketals and quinone imines have been reported to give cycloaddition products at the cyclohexenone oxidation level with a variety of substituted 1, 3-butadienes. A number of spiroketal- and spirolactone-imines were reacted with electron rich butadienes to give adducts. Spectroscopic investigation showed the double bond syn to the sulphonimide group to be the more dienophilic. The butadienes also gave novel adducts with the phenylene monoketal of benzoquinone.

Item Type:	Thesis
Creators:	Hadji-Pavlidis, V.
Date:	1985
ISBN:	9781369325850
Identifiers:	Number Type PQ10290336 Other
Divisions:	Schools > School of Science and Technology
Record created by:	Laura Ward
Date Added:	12 Jul 2021 13:18
Last Modified:	22 May 2024 15:29
URI:	https://irep.ntu.ac.uk/id/eprint/43405

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