I. Catalytic Conjugate Allylation of Alkylidene Malonates Nucleophilic conjugate addition of allylsilanes and allylstannanes to alkylidene malonates under the action of ytterbium catalysis in the presence of hexafluoro-isopropanol has been developed. Enantioselective conjugate allylation of alkylidene malonates under ytterbium or scandium catalysis using chiral bis(oxazoline) ligands allows access to the conjugate addition products in an enantiomerically-enriched form. Furthermore, elaboration of the allylated substrates via decarboxylation and an oxidative cleavage was demonstrated. II. Catalytic Enantioselective Conjugate Addition of Azaarylacetates and Acetamides to Nitroalkenes An enantioselective nickel-catalysed Michael addition of azaarylacetates and acetamides to nitroalkenes has been developed. A range of azaaryl pronucleophiles were shown to react with a variety of nitroalkenes to generate highly functionalised Michael addition products with impressive diastereo- and enantiocontrol. A possible mechanism for this process is proposed and crystal structures of the addition products have also been attained, allowing determination of the absolute stereochemistry. Elaboration and further functionalisation of these products was also possible under a range of conditions.

The aim of this project was to utilize chiral cation-directed catalysis in the asymmetric synthesis of novel hererocycles. This goal was initially realized by the synthesis of azaindolines in high yields and enantioselectivities (Chapter 2). Extension of this methodology to substrates bearing two stereogenic centres was successful, although control over both diastereoselectivity and enantioselectivity in this process was modest. Finally the synthesis of heterocycles utilizing cation-directed rearrangement processes was examined, with proof of concept obtained for a novel asymmetric cyclization to form xanthenes.

Bifunctional iminophosphoranes, containing a triaryl-substituted iminophosphorane and bis(3,5- trifluoromethyl)phenyl thiourea on a single enantiomer scaffold are novel asymmetric superbase organocatalysts reported by the Dixon group in 2014. This thesis describes our efforts to expand their scope and utility in a variety of challenging chemical transformations. Chapter 2 describes the development and application of immobilised bifunctional iminophosphorane organocatalysts. We have successfully immobilised bifunctional iminophosphoranes on a crosslinked polystyrene support and applied this sold-supported catalyst to three challenging asymmetric reactions; namely the nitro-Mannich reaction of phosphinoyl ketimines and the conjugate addition of alkylmalonates and N,N-dimethyl β-keto amides to nitrostyrene. Very good yields, enantio- and diasteroselectivities were obtained in all cases. We have also demonstrated their use in a range of conjugate additions of cyclic 1,3-dicarbonyl compounds to nitroalkenes, which suffered from very slow reaction rates under tertiary amine-based bifunctional catalysis. In all cases, the immobilised bifunctional iminophosphoranes performed very well in comparison to their homogeneous counterparts. We have also demonstrated catalyst recycling over 10 cycles and application in a continuous flow system with a productivity of 7.20 mmol _producth^-1g_catalyst^-1. to the ring-opening polymerisation (ROP) of cyclic esters. We have demonstrated the performance of bifunctional iminophosphorane organocatalysts in the ROP of L-lactide (LA), δ-valerolactone (VL) and ε-caprolactone (CL). The polymerisation of LA and VL proceeded rapidly and was well controlled, while only short lengths (> 100 DP) of poly(CL) could be prepared in a controlled fashion due to hypothesised competing initiation from the catalyst. We have shown that the polymerisation of LA using our catalyst may be considered a living polymerisation. Di-block co-polymers could also be successfully prepared via sequential monomer addition or through the use of macroinitiators. We then investigated the roles of the iminophosphorane and the thiourea component of the catalyst.

This thesis concerns the development of the first BINOL phosphoric acid (BPA) catalysed enantioselective N-acyliminium cyclisation reactions and their incorporation into domino sequences that allow for the construction of architecturally complex enantioenriched polycycles in a single step from easily accessible starting materials. More specifically, this thesis deals with the discovery of a BPA-catalysed enantioselective N-acyliminium cyclisation cascade of enol lactones and tryptamines. Its extension to a doubly catalysed process involving gold(I) to cycloisomerise alkynoic acids and a BPA to effect the enantioselective N-acyliminium cyclisation is presented. In addition, the exploitation of this method in highly diastereo- and enantioselective N-acyliminium cyclisations of oxoacids and tryptamines and in a site isolated base-catalysed Michael addition / acid-catalysed N-acyliminium cyclisation cascade is described. A study on the proposed mechanism and model for the origin of enantioselectivity is discussed, based on experimental data and a computational study. As a separate part of our programme, the development of a new class of stronger Brønsted acids, chiral benzenesulphonic acids, is described. The optimisation of the synthetic routes as well as the synthesis of a library of acids is presented and their assessment in precedented reactions is discussed.