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Title: New methods for the synthesis of functionalised arenes
Author: Bunting, Danielle
ISNI:       0000 0004 8504 8248
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2019
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Arenes are a cornerstone of organic chemistry, and new methods for their functionalisation, whether with improved efficiency, or for the synthesis of novel, highly functionalised skeletons remain crucial. The methods available for achieving such transformations are diverse. This thesis is comprised of two chapters, one investigating the use of ruthenium catalysis for directed C-H functionalisation of arenes possessing a strongly coordinating directing group. The second concerns the use of arynes for the construction of highly functionalised pyridines (via a hexadehydro-Diels-Alder (HDDA) reaction) and ortho-hydroxy biaryls (via a tandem benzyne-Truce-Smiles rearrangement). Ruthenium catalysis has successfully been used to introduce a number of functional groups by C-H activation. Combined with halocarbons, it could be used to introduce novel functionalities such as tetrasubstituted alkenes, or a formyl group in the meta-position of phenylpyridine. Pleasingly, the use of iodine monochloride as a halogenating agent allowed catalyst dependent ortho-halogenation of phenylpyridine substrates. Use of Ru3(CO)12 catalysis resulted in selective iodination, whereas RuCl2(PPh3)3 enabled chlorination. The substrate scope, as well as the reasons behind this intriguing change in selectivity were investigated. Ruthenium catalysis has also been used to achieve a one-pot tandem N,C-arylation of pyrazoles, using both aryl components of diaryliodonium salts, avoiding the waste of one equivalent of aryl iodide. Effective for both symmetrical and unsymmetrical diaryliodoniums in good yields, this could also be extended to the use of styrylphenyliodoniums for synthesis of trisubstituted alkenes. The use of arynes also provides a powerful method for the synthesis of functionalised arynes. Attempts to achieve a pyridyne synthesis and subsequent trapping in a HDDA cascade were unsuccessful. However, generation of benzyne from ortho-trimethylsilyl aryl triflate, followed by nucleophilic attack, and subsequent Truce-Smiles rearrangement of an aryl sulfonate ester was successful in the synthesis of ortho-functionalised biaryls.
Supervisor: Leigh, David ; Greaney, Michael Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: benzyne ; Smiles ; Truce-Smiles ; catalysis ; ruthenium ; C-H activation ; HDDA