Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642657
Title: Development of synthetic routes to novel heterocyclic colour couplers
Author: Cartwright, Dale D. J.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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Abstract:
Studies into a potential new synthetic route to pyrazolotriazole colour couplers showed that flash vacuum pyrolysis (FVP) of 3-methyl-6-phenyl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine produced 1-isothiocyanato-1-phenylethane. The mechanism probably involves a 1,5-shift within the bicycle system to form a spiro-intermediate, which undergoes extrusion of molecular nitrogen and of a substituted nitrile to form a cyclic carbine, the rearrangement of which yields the product. This reaction pathway was found to be general and provided a clean, high yielding route to previously unknown alkyl-substituted alkenylisothiocyanates. A novel synthetic route to various [1,3]thiazolo[3,2-b][1,2,4]triazoles derivatives was discovered through FVP of 4-amino-3-allylthio-4H-1,2,4-triazoles. The mechanism is thought to proceed via initial [3,3]-sigmatropic shift of the allyl group followed by cleavage of the N-N bond to generate a thiaza-allyl radical, which then undergoes stylisation, rearrangement and alkyl group extrusion to give the thiazolotriazole products. This methodology provides a three step synthetic route to thiazolotriazoles with the ability to vary substituents at all three positions on the ring system. A clean and efficient two step route to benzyl type radicals from benzylamine type precursors was developed using FVP of their pinacolone imines. Using this imine derivative of benzylamine as a model system, radical cleavage of the C-N bond produced benzyl radicals (which coupled to give bibenzyl) and an iminyl radical (which cleaved to provide acetonitrile). This methodology was applied to the synthesis of a novel 5,5,5-fused heterocycle, 7H-3-thia-6a-aza-cyclopent[a]pentalene, and a 6,5,5-fused heterocycle, 9H-pyrollo[1,2-a]indole. Further applications of this methodology to new heterocyclic systems were limited due to problematic synthesis of starting materials.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.642657  DOI: Not available
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