Novel main group Lewis acids for synthetic and catalytic transformations

The work described herein is concerned with Lewis acidic triarylboranes for synthetic and catalytic transformations where the influence of different substitution pattern and substituents were crucial in determining the resulting reactivity. Chapter 1 will provide a general introduction into acidity and will lay the theoretical foundation for the ensuing chapters. Chapter 2 introduces the boranes utilised in this work and will give literature examples describing reactivities of the currently known boranes. Besides providing several crystal structures, this chapter will discuss the Lewis acidity of these boranes. Chapter 3 explores the hydroboration of imines catalysed by tris[3,5-bis(trifluoromethyl)-phenyl]borane. By testing a variety of various Lewis acids further insight into the mechanism of this hydroboration is gained. Chapter 4 further investigates borane imine adducts and the impact of the adduct formation on the electronic transitions within the imines. The photoactive adducts are then explored as vapochromic materials towards various solvent vapours. Chapter 5 focuses on the formation of pyrones, dihydropyrones and isocoumarins catalysed by tris(pentafluorophenyl)borane. A cross over experiment reveals the nature of this cyclisation reaction. Chapter 6 investigates the radical character of a frustrated Lewis pairs and their resulting reactivity. A novel protocol for a radical Heck-type reaction is provided and the mechanism was investigated. Finally, Chapter 7 will show the ambiguity between 1,1-carboboration and 1,3-haloboration in the reaction of propargyl esters with dichlorophenylborane