Hydroamination of Alkenes and Alkynes with Group 2 Centred Catalysts

The ever-increasing call upon the world's resources demands that chemists devise ever more inventive means to exploit existing and novel chemical feedstocks. The ramifications of so-called sustainable chemistry (also known as 'green chemistry') impact on all stages of the manufacturing process. This includes improving the efficiency of reactions via advances in engineering, catalysis and synthetic chemistry. Atom efficiency or the atom economy concept is an extremely useful tool for rapid evaluation of the amount of waste generated by alternative routes to a specific product. It is calculated by dividing the molecular weight of the desired product by the sum total of the molecular weights of all substances produced in the stoichiometric equation for the reaction(s) involved. This proposal seeks to develop environmentally benign catalysts for the 100% atom efficient transformation of aminoalkenes and -alkynes into valuable heterocyclic compounds. Although this type of transformation is precedented in a series of lanthanide catalysts, our approach utilises the very much understudied, but inexpensive, elements of group 2, the alkaline earths. In exciting preliminary work we have shown that a simple prototype calcium complex is capable of catalysing the cyclisation of a number of substrates with activities far exceeding those reported for more elaborate lanthanide-based species. These studies also highlighted, however, a deficiency of out initial catalyst; its tendency to redistribute to catalytically inactive species over the course of the reaction. We now wish to extend this work with catalysts that will be much less prone to these detrimental processes. These will utilise tripodal borate ligands based upon pyrazole and N-heterocyclic carbene donors. Although the latter class of ligand is almost completely unexplored, further preliminary work has indicated that the strong donor properties of the ligand will prove ideal for the stabilisation of group 2 centres, while the straightforward synthesis also holds promise for the development of new chiral ligands for enantioselective catalysis. Our proposal therefore is an ideal combination of novel academic and applied motivation that will provide an excellent, but challenging, training environment for a capable PhD candidate.