Light triggers select isomers to flip

Abstract

Converting a mixture of mirror-image forms, or stereoisomers, of a molecule into a single isomer is a big deal in making pharmaceuticals, because usually only one isomer is useful as a drug. But current options for this process, called deracemization, are complicated and fiddly. Research by Sanzhong Luo and coworkers at Tsinghua University and the Haihe Laboratory of Sustainable Chemical Transformations has now made it as simple as turning on a light. The group used an iridium compound, an enamine, and violet light to transform a mixture of branched aldehyde isomers into a single one ( Science 2022, DOI: 10.1126/science.abl4922 ). The work combines two well-understood reactions: double-bond photoisomerization and enamine catalysis, which was recognized with the 2021 Nobel Prize in Chemistry . The group’s straightforward approach can be used to deracemize mixtures of many types of chiral aldehydes. The method works by transferring the chirality, or handed-ness, from the