Development of gold(I)- and indium(III)-catalysed reactions
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This thesis contains an introductory chapter to gold(I)- and indium(III)-catalysis, followed by five chapters outlining the research undertaken by the author during the duration of study. Chapter 1 gives an introduction to gold(I)- and indium(III)-catalysis and, in particular, focuses on the reported literature on the development of the gold(I)-catalysed reactions of allenes. Chapter 2 describes the research undertaken into the dehydrative thiolation of allenols, and the discovery of InCl3 as a superior catalyst for this reaction compared to Au(I). The use of InCl3 as a catalyst provided excellent regioselectivities of the desired 1,3-diene products in good to excellent yields. Several reactions were carried out using a gold(I) catalyst for comparison, but they consistently provided lower yields and poorer regioselectivities. Mechanistic studies outlining the differences between Au(I) and In(III) are also discussed. Chapter 3 details the developments on the dehydrative reactions of allylic alcohols to form allylic ethers, with an In(III) vs. Au(I) comparison. These investigations show that InCl3 can be used as a cheaper alternative to Au(I) for this reaction and, in some cases, outperforms Au(I). In particular, In(III) exhibited superior performance as a catalyst when substrates or nucleophiles contain pendent π bonds. Chapter 4 presents the successful development of a mild protodeboronation reaction of boronic acids under gold(I)-catalysis. Additive free conditions and the use of “green” solvents provides a mild reaction with an excellent functional group tolerance. This method can be adapted for a regioselective ipso-deuteration technique which would be useful in labelling studies. Mechanistic investigations are also discussed. Chapter 5 outlines a quick and efficient iododeboronation reaction which can be carried out in “green” solvents in under 10 mins, making this reaction potentially useful for radiolabelling studies. Chapter 6 describes the first intermolecular gold(I)-catalysed chirality transfer hydroalkoxylation reaction of 1,3-disubstituted allenes. These reactions proceed with excellent regioselectivity and a high degree of chirality transfer. Mechanistic studies are also discussed.