A group of scientists at Chiba University has devised a creative, time-efficient way to greatly reduce the process required for various organic chemistry reactions, like those used in developing pharmaceuticals, potentially streamlining and cost-reducing drug development.
Samarium’s Untapped Potential
Samarium (Sm) is a rare earth metal that has the long-standing ability to complete single-electron transfer reductions, and this behaviour also makes it an important material in organic chemistry. One of its divalent compounds, samarium iodide (SmI2), is fairly stable and will function under mild conditions at room temperature, which is especially useful in generating pharmaceuticals and bioactive materials.
Nevertheless, the classical applications of SmI2 have been limited by its stoichiometric use in large amounts and employment of hazardous reagents, making the process resource-consuming and difficult to control. Scientists have long been working to minimize the amount of Sm needed, although most of the methods currently used in commercial production today still call for large quantities of the material — typically 10% to 20% of the raw materials.
A Visible-Light Breakthrough
A new class of catalysts can be prepared by a research team led by Assistant Professor Takahito Kuribara at the Institute for Advanced Acaedmic Research and Graduate School of Pharmaceutical Sciences, Chiba University which could potentially replace [Sm] with minimal amounts used in these important organic chemistry transformations.
It works because the collaboration between the tripled samarium ion and a particular 9,10-diphenyl anthracene (DPA)-substituted bidentate phosphine oxide ligandringe. Employing a peptide-based ‘visible-light antenna’ ligand allows for the Sm-catalyzed reductive transformation to be carried out using low-energy visible light, which minimizes the load of Sm required.
Antenna ligands are documented to have some role in the photoexcitation of lanthanoid metals such as Sm, as Assistant Professor Kuribara notes. In our past work, a DPA-substituted secondary phosphine oxide ligand that undergoes redox-chemistry with visible light was designed (Figure 1). Building on this, we crafted a novel visible-light-activated DPA-substituted bidentate phosphine oxide ligand that obviates the need for stoichiometric amounts of Sm.
Conclusion
The development by the Chiba University research group, this time not only organic chemistry is a major step forward, allowing both efficient and catalyzed Sm-catalysed reductive transformations to be performed under mild conditions with low loadings of Sm. Thanks to this approach, visible light was efficiently used as an energy source and a new so-called ‘visible-light antenna’ ligand was synthesized to rectify the well-known limitations of traditional Sm-based reactions and deliver greener and more sustainable drug developments. This groundbreaking technique could create a new dimension in the science of organic chemistry.
