Beyond metal purity with upcycled rare earth mixtures from electronic waste for enantioselective synthesis

The development of homogeneous catalysts traditionally relies on highly purified metals, a requirement that is particularly challenging for rare-earth elements due to their chemical similarity and energy-intensive separation processes. Here we demonstrate that mixtures of rare-earth elements recovered from electronic waste can serve directly as effective precatalysts for asymmetric catalysis. A lanthanide triflate mixture derived from spent NdFeB magnets (composed primarily of Nd with minor amounts of Pr, Dy and Tb) efficiently promotes Diels–Alder cycloadditions in combination with chiral PyBox ligands. Across a range of dienes and dienophiles, the mixed-metal catalyst exhibits chemical yields, diastereoselectivities and enantioselectivities that are comparable to, and in some cases superior to, those obtained with pure neodymium triflate. Control experiments indicate that the catalytic performance is largely preserved despite the presence of multiple lanthanides. The practical relevance of this approach is demonstrated by gram-scale synthesis of prostaglandin intermediates, including the Corey lactone precursor, a key building block for prostanoid pharmaceuticals used in glaucoma treatment. These findings challenge the conventional paradigm of single-metal catalyst purity and establish electronic waste as a viable rare-earth catalyst platform for asymmetric synthesis. The development of homogeneous catalysts has traditionally relied on highly purified metals, a requirement that is particularly challenging for rare-earth elements because of their closely related chemical properties and the energy-intensive processes required for their separation. Here, the authors demonstrate that mixtures of rare-earth elements recovered from electronic waste can be used directly, without prior separation into individual pure elements, as effective precatalysts for asymmetric catalysis.