Tailored quinones support high-turnover Pd catalysts for oxidative C–H arylation with O ₂

A subtle balancing act for quinones Palladium catalysis is widely used in drug synthesis to form carbon-carbon bonds, but typically both carbon centers need to be activated ahead of time. Although introducing oxygen as an oxidant diminishes the need for preactivation, the catalysis then tends to be less efficient, especially in the case of arene coupling. Salazar et al. pinpointed the role of quinone co-catalysts in these processes and determined that after accelerating carbon-carbon bond formation, the quinone slows down catalyst reoxidation by oxygen. Appending bulky substituents to the quinone struck a better balance and substantially enhanced catalytic efficiency. Science , this issue p. 1454