The first general examples of direct coupling of heteroaryl chlorides, especially substituted 2-pyridyl chlorides which were previously found to be problematic, with electron-deficient polyfluoroarenes are reported. Pd(OAc)₂ associated with 3-(dicyclohexylphosphino)-2-phenylindole L1 serves as the effective catalyst which allows the challenging direct coupling of heteroaryl chlorides and polyfluoroarenes. In addition to heterocycles, a wide range of non-activated and activated aryl chlorides and alkenyl chlorides were also applicable under this catalyst system. A catalyst loading down to 1 mol % Pd can be achieved.

An intermolecular CH arylation of unactivated arenes with aryl iodides is made viable through a transition-metal-free approach. This simple and efficient process obviates the common use of diamines or diols as the promoters. With the aid of only mixed potassium alkoxides, a number of unactivated arene CH bonds can be directly arylated through a homolytic aromatic substitution (HAS) pathway.

Transition-metal-free cross-coupling reactions have been a hot topic in recent years. With the aid of a radical initiator, a number of unactivated arene CH bonds can be directly arylated/functionalized by using aryl halides through homolytic aromatic substitution. Commercially available or specially designed promoters (e.g. diamines, diols, and amino alcohols) have been used to make this synthetically attractive method viable. This protocol offers an inexpensive, yet efficient route to aromatic CC bond formations since transition metal catalysts and impurities can be avoided by using this reaction system. In this article, we focus on the significance of the reaction conditions (e.g. bases and promoters), which allow this type of reaction to proceed smoothly. Substrate scope limitations and challenges, as well as mechanistic discussion are also included.