Research in the Melen group focuses on the use of main group Lewis acids in organic synthesis and catalysis. The research programme includes:
• Main group catalyst design including tuning the steric and electronic effects of the Lewis acid.
• Applications of main group Lewis acids in organic synthesis and catalytic processes.
• Mechanistic studies to determine reaction pathways and the role of the Lewis acid in the reactions using combinations of experimental and theoretical methods.
Catalysts are used widely in the industrial setting and provide a lower energy reaction pathway to occur without consumption of the catalyst. To date, many catalysts typically employed are centred on the so called 'precious metals' and, so far, transition metals have dominated homogeneous and heterogeneous catalysis. But is the behaviour of transition metals so notably different from the main group elements? Our research aims to uncover patterns of reactivity which bridge the apparent divide between transition metal and main group chemistry, by demonstrating that p-block elements can catalyse a variety of industrially significant reactions.
The softer side of boron:
Recent contributions by the Melen group to the field of main group mediated organic transformations include the exploration of Lewis acidic main group compounds as reagents for enabling transformations which are typically promoted or catalysed by heavier d-block metals such as Au(I). This includes the use of Lewis acidic boranes to generate a range of pharmaceutically important heterocycles.
Angew. Chem. Int. Ed., 2017, 56, 11995; Angew. Chem. Int. Ed., 2016, 55, 11292; Chem. Eur. J., 2016, 22,14618.
As main-group chemistry, in particular boron chemistry, has expanded and developed over the past 20 years, one reagent has risen to prominence as well. Tris(pentafluorophenyl)borane, B(C6F5)3 (commonly known as BCF), has demonstrated extensive applications in a wide variety of reactions, including borylation, hydrogenation, hydrosilylation, frustrated Lewis pair (FLP) chemistry, Lewis acid catalysis, and more. However, as main-group chemistry continues to evolve as a field, new reagents are required that go beyond BCF, increasing not only the range of reactions available but also the breadth of compounds attainable. Our research focuses on the development of new borane Lewis acids and advancing novel borane and borocation usage that eclipses that of the stalwart BCF.
Chem. Eur. J., 2017, 23, 10997; Organometallics, 2017, 36, 2381; Inorg. Chem., 2017, 56, 8627; Chem. Eur. J., 2016, 22,14618
New Directions in Metal-Free Catalysis:
Recent developments in the Melen group have investigated new directions in metal free catalysis to provide new openings in both the synthesis and applications of main group compounds. This includes enantioselective catalysis using borenium cations, combining FLP hydrogenation with organocatalysis and applications of main group chemistry into flow systems.
ACS Catalysis, 2017, 7, 7748; Adv. Synth. Catal., 2017, 359, 2580; Dalton. Trans., 2016, 45, 15303
International: Fontaine (Laval, Canada), Goswami (Ropar, India), Hashmi (Heidelberg, Germany), Oestreich (TU Berlin, Germany), Stephan (Toronto, Canada)
Cardiff: Browne, Harris, Luk, Morrill, Newman, Platts, Pope, Richards, Wirth