With ultraviolet light, Massachusetts Institute of Technology researchers have developed another potential industrial route to organophosphorus compounds that avoids toxic, tough-to-handle chlorine. Phosphorus atoms abound in pesticides, fertilizers, and more. But to make these compounds from naturally available white phosphorus, P4, researchers have typically resorted to treating P4 with chlorine gas to make PCl3, and then reacting PCl3 with organic molecules. Daniel Tofan and Christopher C. Cummins have now used a photochemical approach instead to generate cyclic organophosphorus compounds called diphosphanes directly from P4 (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201004385). They suggest the strategy could complement other chlorine-free methods, including some already developed by Cummins’ group (C&EN, Aug. 9, page 8). Inspired by research published more than 70 years ago, Tofan and Cummins exposed a mixture of P4 and an organic diene to UV light for half a day, obtaining diphosphane products. The outcome indicates that P2, a molecule unstable under typical organic synthesis conditions, is likely made during the course of the reaction, Cummins says. In the future, he hopes to catch P2 in the act.