Studies in the Cycloheptane Field

Still, Ian William James (1961) Studies in the Cycloheptane Field. PhD thesis, University of Glasgow.

Abstract

In Section I, some of the reactions of tropilidene (or cycloheptatriene) are described. Attempts to convert tropilidene directly into tropone, or the so far unknown tropyl alcohol, by employing a variety of common oxidative procedures, have been unsuccessful. Active manganese dioxide, sodium dichromate, and performic acid all led to the formation of benzaldehyde in varying amounts. Attempts to epoxidize tropilidene, using monoperphthalic,perbenzoic, and performic acids, have likewise met with no success. The latter part of Section I deals with the evidence obtained for the structures of the previously described bromine and hydrogen bromide addition products of tropilidene. In both cases it seems likely that a 1,2-addition mechanism is involved. Attempts to prepare hypobromous acid and ethyl hypobromite addition products were not successful --- considerable amounts of benzaldehyde being produced in each case. In Section IIa, synthetic work is described, which establishes the nature of the dehydration product of 2-hydroxy-2,6,6-trimethylcyclohept-4-en-l-one. This hydroxy-ke tone was obtained previously as a product of the selenium dioxide oxidation of alpha-dihydroeucarvone. Ring-contraction occurs on dehydration with the formation of 1-acety1-5,5-dimethylcyclohexa-1,3-diene. This ketone has been synthesized from 5,5-dimethylcyclohexay-l,3-dione (dimedone), while its tetrahydro-derivative, 1-acety1-3,3-dimethylcyclohexane, has also been synthesized from 3-methyloyclohex-2-en-l-one. A number of oxidative degradations are also described in Section IIa, with a view to establishing the position of the double bond in a-dihydroeucarvone. These experiments were inconclusive, but the results of isomerizations to the conjugated beta-dihydroeucarvone, in conjunction with the evidence obtained by vapour phase chromatography, indicated that alpha-dihydroeucarvone is in fact a mixture containing 75% of the gammadelta-unsaturated ketone, and 25% of the betagamma-unsaturated ketone. This conclusion is confirmed by the nuclear magnetic resonance data. A dimeric product, or mixture of products, obtained by the action of alkali on eucarvone is briefly described. In Section IIb, the conversions of eucarvone into carenedione, and eucarvone trityl enol-ether are described. Various attempts to oxidize these bicyclic derivatives, with a view to the synthesis of the naturally occurring monoterpene, chamic acid, were unsuccessful. Oximino-eucarvone, or carenedione monoxime, was converted to the corresponding diazo-ketone, which underwent thermal isomerization in the presence of air to yield carenedione. No useful results were obtained from attempted Beckmann rearrangements of oximino-eucarvone, but this compound yielded interesting iso-oxazolino rearrangement products on treatment with sulphuric acid. The structures of those products have been fully elucidated by hydrogenolytic cleavage to known derivatives of carvacrol. Some interesting features of the ultra-violet absorption spectra of the rearrangement products and their derivatives are discussed. Finally, the action of hot dilute acid on carenedione has afforded a rearrangement product, which may be a mixture of two hydroquinone derivatives. The evidence so far obtained for the two structures is discussed. The irradiation of carenedione yielded what appeared to be a hydroxy-lactone, but very little evidence has been obtained for its structure.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Organic chemistry
• Date of Award: 1961
• Depositing User: Enlighten Team
• Unique ID: glathesis:1961-79417
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 05 Mar 2020 10:01
• Last Modified: 05 Mar 2020 10:01
• URI: https://theses.gla.ac.uk/id/eprint/79417