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Title: Iridium-catalysed cleavage and formation of unstrained aliphatic carbon-carbon bonds
Author: Fernandez Gimenez, Marta
ISNI:       0000 0004 7428 5782
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
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This thesis discusses the study of the cleavage and the formation of unstrained aliphatic carbon-carbon bonds mediated by homogeneous iridium catalysts. The main project of this thesis consists in mechanistic studies of Ir-catalysed selective, reductive cleavage of unstrained C-C single bonds in dinitriles. Whereas the second project focuses on the development of a novel methodology for the catalytic C-C bond formation via a Michael-type hydroalkylation reaction envisioned as a result of our mechanistic studies. Chapter 1 contains a review of transition-metal catalysed cleavage of C-C single bonds and a discussion of the existing strategies to facilitate the cleavage of these highly stable bonds and the relevant progress in this field. Particularly, this review is focused on reported examples of catalytic reductive cleavage of unstrained C-C single bonds. This overview highlights the lack of mechanistic understanding of this transformation which encouraged us to initiate our research. Chapter 2 discusses the mechanistic studies of Ir-catalysed selective, reductive cleavage of unstrained carbon-carbon single bonds in dinitriles. Our experimental and computational results allowed to propose that this process occurs via C-H activation followed by retro-Michael type reaction involving alkene deinsertion. Our investigations also provide understanding about the driving force of the process that enables this thermodynamically unfavourable transformation. Moreover, the results of the mechanistic studies evidence that the C-C bond cleavage is a reversible process. These findings allowed us to develop a new catalytic method for the formation of C-C bonds catalysed by the same iridium catalyst employed for the cleavage process. Thus, Chapter 3 provides a discussion of our research on the iridium-catalysed Michael-type hydroalkylation of cyclic a,ß-unsaturated ketones with alkyl aryl nitriles. This method provides a facile access to 3-substituted cyclohexanones containing a quaternary carbon atom. To exemplify the synthetic utility of these new compounds, we then conducted preliminary studies on the catalytic dehydrogenation of 3-substituted cyclohexanones to meta-substituted phenols that are difficult to obtain via common synthetic routes.
Supervisor: Sergeev, Alexey Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral