Methylene activation reached new heights

An organic synthesis method that took flight this year could prove to have an unusually wide wingspan. Developed by Jin-Quan Yu and coworkers at Scripps Research Institute California after a 14-year effort, the reaction advances a long-standing goal: activating specific C–H bonds in organic compounds and converting them catalytically and enantioselectively into C–C bonds or other derivatives. Since there’s no shortage of C–H bonds in organic compounds, the technique has lots of potential for widespread applicability. Specifically, the new reaction uses a palladium catalyst and quinoline-based ligand to convert β-methylenes—CH2 groups two carbon atoms away from amides or carboxylic acids—into chiral centers (Science 2016, DOI: 10.1126/science.aaf4434). Synthetic organic chemists had previously developed ways to activate several types of C–H bonds, such as by preinstalling activating groups in substrates. But the ability to target C–H bonds of unactivated methylene groups and then derivatize them catalytically and enantioselectively had been largely unsolved.