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Title: A radical approach towards the synthesis of novel pyridine and pyrimidine based heterocycles
Author: Walji, Dhiran
ISNI:       0000 0004 2690 979X
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2009
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A series of N-acylated and –alkyated aminobromopyridines were prepared, and under 2,2’-azobisisobutyronitrile (AIBN) initiation in the presence of n-tributyltin hydride (Bu3SnH), readily underwent cyclisation to produce 4-aza and 7-azaoxindole derivatives. Upon recrystallisation in polar solvents in the presence of atmospheric oxygen, these compounds were found to undergo quantitative autoxidation.  Inspection of NMR and MS data suggest that the mechanism proceeds by hydrogen abstraction to form a hydroperoxide intermediate. The second part of the study reveals a simple and effective synthesis towards pyrrolo[2,3-d]pyrimidine derivatives as substitutes for purine analogues.  The purine-type nucleus is secured via tributyltin hydride mediated radical cyclisation, which provides a convenient route to access compounds for studies of biological activity and structure activity relationships. The third part describes radical addition of iodopyridines and functionalised pyrimidines to arenes, effected under mild conditions using tris(trimethylsilyl)silane and oxygen to promote the bimolecular radical addition pathway.  Initial reactions yielded intractable pyridine products with tris(trimethylsilyl)silane by-products. This was overcome by initial quaternisation of the heterocycles. The fourth part of the study  concerns the synthesis of the pyrimidine backbone unit of the natural product isolated from the heterostemma brownii.  This was obtained by the regioselective radical addition of halopyrimidine to electron-deficient methyl methacrylate (MMA). The final part describes the radical translocation reaction and the effect of variation in cycloalkane ring sizes and electron-donating ability.  This provided a route towards horsfiline derivatives. Under the high temperatures experienced by the horsfiline precursors this serendipitously yielded macrocyclic pyrimidines.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Heterocyclic chemistry ; Pyridine