Simplifying Iron-Phosphine Catalysts for Cross-Coupling Reactions

摘要

Iron-phosphine complexes are emerging as an excellent choice of catalysts in a range of C—C bond-forming processes. and yet the "rules" for determining selection of the most appropriate phosphine ligands are, at present, far from clear. For example, complexes 1 and 2, which are based on phenylene bis(phosphine) ligands, seem to occupy a privileged position, displaying, to date, unsurpassed performance in the cross-coupling of alkyl halides in terms of the variety of nucleophilic substrates that they tolerate. But are these systems genuinely unique or can simpler catalysts based on cheaper, more widely available bisphosphines be exploited instead? We now show that an understanding of the likely nature of the active catalyst allows the development of far simpler catalysts based on the widely available and inexpensive ligand bis(diphenylphosphino)ethane (dppe).