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Title: Nickel-catalysed reductive aldol cyclisation : scope and mechanistic insight
Author: Fordyce, Euan Alexander Fraser
ISNI:       0000 0004 2730 9163
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2009
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A highly diastereoselective nickel-catalysed reductive aldol cyclisation is described. Using Ni(acac)2 as a precatalyst and diethylzinc as a stoichiometric reductant, various α,β-unsaturated carbonyl compounds tethered through an amide or ester linkage to a ketone electrophile underwent efficient cyclisation to afford β-hydroxylactams and β-hydroxylactones respectively. The scope of this process is broad with variation in the α,β-unsaturated carbonyl component, ketone and, where applicable, the nitrogen protecting group all tolerated. A series of experiments, including deuterium-labelling studies, were carried out in an attempt to gain insight into the possible reaction mechanisms that might be operative. II. Development of Novel Methodologies for the Silylation and Stannylation of Base-Sensitive Cyclopropenes Two distinct approaches to the synthesis of silyl- and stannylcyclopropenes are described. Using substoichiometric quantities of Cu(acac)2 and 1,2-bis(diphenylphosphino)ethane in combination with (trifluoromethyl)trimethylsilane, a diverse range of 1,3,3-trisubstituted cyclopropenes underwent direct silylation to afford the corresponding 1-silylcyclopropenes in good to excellent yield. Attempts to adapt these conditions to synthesise the corresponding stannylcyclopropenes proved unsuccessful. However, by employing (pentafluoroethyl)tributylstannane and stoichiometric potassium fluoride, it was possible to access 1-stannylcyclopropenes in comparable yields. It was also demonstrated that both the stannyl- and silylcyclopropene derivatives synthesised using these methodologies were able to serve as precursors for a variety of novel molecules that might otherwise be difficult to access using alternative methods.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: nickel-catalysed reductive aldol cyclisation ; deuterium-labelling studies ; synthesis of silylcyclopropenes ; silylcyclopropene derivatives