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Title: Cyclometalated rhodium complexes for selective transfer hydrogenation
Author: Aboo, Ahmed Hamdoon
ISNI:       0000 0004 7656 8217
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2019
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Selective transfer hydrogenation of aldehydes and α,β-unsaturated carbonyl compounds is some of the most attractive and challenging transformations found in both industry and academia. However, the chemo-selective reduction of such compounds is challenging, especially when methanol is employed as the source of hydrogen and the reaction solvent. My thesis contributes to the development of new rhodium catalysts that enable the use of abundant and easy-to-handle methanol for the reduction of aldehydes and α,β-unsaturated carbonyls with high selectivity under mild reaction conditions. Chapter 1 provides an introduction covering the area of transfer hydrogenation of C=X (X = C, O) bonds, and the use of methanol as a hydrogen donor. It also describes previous cyclometalated complexes and their recent developments in the area of transfer hydrogenation, including the previous work that has been developed by our group. Chapter 2 describes the use of rhodium complexes 'rhodacycles' for the selective transfer hydrogenation of a wide range of aromatic aldehydes in the presence of various sensitive functional groups. The reduction was carried out using methanol as both the reaction solvent and hydrogen donor. Chapter 3 follows the successful reduction of the aldehydes, presenting a rhodium complex that has shown to be capable of the selective reduction of the C=C double bond moiety within α,β-unsaturated ketones to give corresponding saturated ketones. Substituted chalcones and benzylideneacetophenones are efficiently reduced under this catalytic system. Chapter 4 is an expansion of Chapter 3. The rhodium complex shows high efficiency for the transfer hydrogenation of α,β-unsaturated aldehydes at room temperature with the use of methanol as a source of hydrogen. Chapter 5 establishes a new method for the selective reduction of mono- and di-aldehydes. A rhodium complex has been found to be highly effective for the selective reduction of mono- and di-aldehydes under mild reaction conditions using formic acid as a hydrogen source. Chapter 6 presents the conclusion and the perspectives of all the work covered in this thesis.
Supervisor: Xiao, Jianliang Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral