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Title: Photochemistry of pyrroles and other heterocycles in batch and flow
Author: Maskill, Katie G.
ISNI:       0000 0004 5923 2113
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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This thesis is split into three sections. The first presents the discovery and development of a novel photochemical cycloaddition/rearrangement sequence of electron deficient N-butenyl pyrroles to form fused tricyclic aziridines. The reaction proceeds via two photochemical steps, the first of which is reversible and is mediated in the forward direction by short wavelength DV around 254 run. The backwards reaction and the second step of the sequence are facilitated at longer wavelengths around 312 nm. Detailed mechanistic studies have shown that the second step proceeds via a triplet mechanism as it is quenched by isoprene The scope of this reaction has been studied thoroughly. An electron withdrawing group is required at the 2-position of pyrrole, and extra functionality around the ring is well tolerated. The use of indoles and imidazoles as alternative heterocycles has been investigated, and a number of alkene and non-alkene tethers of branched, linear and cyclic nature have been applied. Pyrroles containing the alkene tether at the C3 position have also been subjected to this reaction and have been found to yield interesting cyclobutane structures. The second section describes the application of this methodology to the synthesis of alkaloid natural product dendrobine. While the synthesis was not completed, important observations were made, leading to the identification of limitations within this methodology. Complex, cyclic tethers are not always tolerated and can facilitate an alternative reaction pathway Finally, a thorough and comprehensive investigation into flow vs. batch photochemistry is presented. Twelve photochemical reactions, after independent optimisation under both batch and flow conditions, were found to give strikingly similar yields with the productivity of a three layer FEP flow reactor being around 20% higher than batch. The safety advantage of carrying out hazardous reactions on flow is also illustrated. In light of the results, a set of general guidelines for first time and experienced photochemists alike is presented
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available