Rhodium-Catalyzed Intermolecular C–H Silylation of Arenes with High Steric Regiocontrol

Silicon Siting The synthesis of many pharmaceutical and agrochemical compounds requires selective functionalization of multiple different sites on aromatic ring frameworks. The size and electronic properties of the first substituent added can influence where the next one is likely to end up. Cheng and Hartwig (p. 853 , see the Perspective by Tobisu and Chatani ) discovered a rhodium-catalyzed reaction that is particularly sensitive to size that places a silicon substituent as far away as possible from the largest group already on the ring. The silicon group can then be replaced with carbon, oxygen, nitrogen, or halide substituents as needed.