Dearomatisation reactions and a novel route to substituted indoles

This Thesis describes the development of silver-catalysed dearomatising spirocyclisation reactions of alkyne-tethered aromatic and heteroaromatic systems. An overview of dearomatisation methodologies and spirocyclisation strategies involving alkyne activation are discussed in Chapter 1. Chapter 2 describes a novel silica-supported silver-catalysed spirocyclisation method. This strategy was applied to a range of aromatic ynone systems and mechanistic information suggesting the involvement of silver nanoparticles in the spirocyclisation process is also reported. This silica-supported spirocyclisation reaction was then applied to a range of phenol-tethered ynones furnishing spirocyclic dienone products which is the focus of Chapter 3. Some preliminary asymmetric spirocyclisation studies using silver salts of chiral phosphoric acids (CPAs) are also described as well as a formal synthesis of the natural product spirobacillene A.
A novel Ag(I)-catalysed synthesis of substituted indoles using pyrrole-tethered alkynes is detailed in Chapter 4. Density functional theory (DFT) calculations are described which suggest that benzannulation proceeds initially via spirocyclisation at the pyrrole C-3 position before undergoing subsequent rearrangement to deliver the indole products. Chapter 5 describes the divergent reactivity of phenol-/anisole-tethered α-diazocarbonyls. Four products (cyclopropanes, tetralones, 1,2-dicarbonyls and spirocycle) were accessed through distinct reaction pathways in which the outcome was dependent on the catalyst used and the nature of the aromatic oxygen substituent.