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Title: Studies on the synthesis and reactivity of bridgehead-fused 1,2,3-triazoles
Author: Connolly, Stephen
ISNI:       0000 0001 3561 3438
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1985
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The subject matter of this thesis is concerned with investigations of the synthesis and reactivity of bridgehead - fused 1,2,3 -triazole derivatives. In particular the synthetic usefulness of the products derived by acid -promoted triazole ring cleavage in such heterocyclic systems was investigated. The description of the results obtained in these studies is preceded by a survey of methods commonly employed for the con- struction of bridgehead -fused 1,2,3 -triazoles and an outline of the types of reactivity which these compounds can exhibit. The reactivity of a series of 3- phenyl- 1,2,3 -triazolo- [1,5-a]pyrimidines towards protic acids has been studied and it has been shown that in the case of hydrochloric and hydrobromic acid triazole ring scission proceeds smoothly to afford the respective 2- halobenzylpyrimidine derivatives. Attempts to effect this reaction with a variety of other protic acids was largely unsuccessful. The ability of Lewis acids to catalyse triazole ring scission of 3- phenyl -1,2,3- triazolo[1,5- a]pyrimidines was also investigated and it was found that the latter reacted with boron trifluoride -etherate to give triazole cleaved products. The intermediate boron trifluoride -1,2,3- triazolo[1,5- a]pyrimidine adduct in such reactions was successfully isolated but attempts to induce triazole ring cleavage of the complex by heating with a variety of alkali metal salts met with mixed success. Attempts to synthesise 2- aminobenzylpyrimidines by the reaction of 2- chlorobenzylpyrimidines with aminating reagents were not successful. In contrast it was found that the synthetically useful 2- aminobenzylpyrimidines could be prepared by the reduction of the corresponding 2- azidobenzylpyrimidines. Acid -catalysed decomposition of the latter compounds also provided a general route to 2- benzoylpyrimidines and the chemistry of these little studied ketones was investigated. However, attempts to use 2- benzoylpyrimidines to prepare novel bicyclic heterocycles failed. 2- Aminobenzylpyrimidines were readily acylated by a variety of acid chlorides and the resulting amides reacted with phosphoryl chloride in 1,2- dichloroethane to give imidazo[1,5 -a]- pyrimidine derivatives. The scope of this two -step acylationcyclisation procedure was investigated in detail and provides a general route to the little studied imidazo[1,5- a]pyrimidine nucleus. 1,2,3- Triazolo[1,5 -a]- 1,3,5 -triazine derivatives were prepared and the reactivity of this virtually unknown ring system towards acid -promoted triazole cleavage was investigated. In many cases such scission proceeded smoothly and provided a new route to 1,3,5 -triazine derivatives. Attempts to synthesise imidazo[1,5- a]- 1,3,5 -triazines failed due to the instability of the 2- azidobenzyl- 1,3,5 -triazines required as precursors of the key intermediate 2- aminobenzyl- 1,3,5 -triazines.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Organic chemistry