Melen Research Group Cardiff University
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.
The Lewis acidic nature of Main Group compounds can be tailored electronically and sterically by substituents. We have implemented the Lewis-acid nature of Main Group compounds to drive a range of important chemical transformations which have potential applications in the synthesis of pharmaceutically important organic heterocycles and/or in materials chemistry. Recent results have shown that the boron Lewis acid B(C6F5)3 could promote both stoichiometric (and catalytic) organic cyclisation processes in heterocyclic synthesis. These studies established that B(C6F5)3 was capable of acting in a similar way to transition metal catalysts allowing the conversion of propargyl amides into oxazoles. Depending on the substituents R and temperature, we were able to identify almost every intermediate in the reaction pathway.
However, the main group Lewis acidic B(C6F5)3 can lead to some very different outcomes than those observed for transition metal catalysed transformations. For example, replacement of the propargyl amide by a propargyl ester leads to marked differences in reactivity. Relating to this, the reactions of B(C6F5)3 with propargyl esters yield allyl boron reagents which can undergo addition to aldehydes to afford novel aldol products in a one-pot reaction.