New Access Point For Trifluoromethyl Arenes

Aromatic rings bearing a trifluoromethyl group are important structural units in bioactive molecules used as drugs and pesticides, prompting organic chemists to find as many ways as possible to install CF₃ groups on arenes. Early trifluoromethylation methods required harsh reagents and reaction conditions and often had poor yields. Researchers have been overcoming those limitations by learning how to use efficient transition-metal reagents under mild conditions to trifluoromethylate C–H bonds and halide or boronic acid groups of arenes. For added flexibility, a research team led by Yao Fu of the University of Science & Technology of China has now developed a procedure starting from aryl amines (J. Am. Chem. Soc. 2013, DOI: 10.1021/ja404217t). The copper-catalyzed method is an adaptation of the Sandmeyer reaction, which is typically used to convert an aryl amine to hydroxyl, cyano, or other derivatives. Fu and coworkers show that CF₃ groups can be easily introduced to arenes and heteroarenes by treating aryl amines with Umemoto’s trifluoromethylating reagent, copper powder, and an alkyl nitrite. The team tested its method by synthesizing the antiarthritis drug leflunomide.