Title:
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Synthesis and reactions of unstable activated nitrogen-containing enophiles
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The work described in this thesis has been concerned with investigations into the synthesis of activated cyclic enophiles attached by a linker group to a basic moiety and their reactivity in the ene reaction. The types of enophiles studied fall into three classes, viz the five-membered triazolinediones, six-membered diazaquinones and the five-membered imidazolinediones. Also investigated was the amidoalkylation reaction of the acyclic imine, 1,2-diethoxycarbonyl aldimine (EtO2CN=CHCO2Et). Hydrogenated precursors to the triazolinediones, i.e. urazoles, were synthesised by reaction of the relevant diamine with hydrazodicarbonamide because the normal synthetic routes using ethyl carbazate were found to be unsuccessful for basic functionalised urazoles. A variety of urazoles were synthesised and in turn subjected to chemical oxidation using a range of oxidants in the presence of an active alkene to bring about an ene reaction. No ene reaction was observed in any case and the triazolinedione reacted with itself to give complex mixtures. Hydrogenated precursors to the diazaquinones were synthesised from bromosuccinic anhydride, hydrazine and the required amine. These compounds also failed to give any ene reaction when reacted with alkenes normally active under such conditions. Reasons for this are discussed. Progress was also made towards the synthesis of ethanolic precursors to the relevant cyclic imidazolinediones. Acyclic amine-containing compounds were prepared but these precursors failed to ring close without decomposition. This aspect was shown to be a key feature of such a ring structure by the successful synthesis of the non-ethanolic containing hydantoins.
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