The crucial role of silver()-salts as additives in C-H activation reactions: overall analysis of their versatility and applicability

Transition-metal catalyzed C-H activation reactions have been proven to be useful methodologies for the assembly of synthetically meaningful molecules. This approach bears intrinsic peculiarities that are important to be studied and comprehended in order to achieve its best performance. One example is the use of additives for the in situ generation of catalytically active species. This strategy varies according to the type of additive and the nature of the pre-catalyst that is being used. Thus, silver( i )-salts have proven to play an important role, due to the resulting high reactivity derived from the pre-catalysts of the main transition metals used so far. While being powerful and versatile, the use of silver-based additives can raise concerns, since superstoichiometric amounts of silver( i )-salts are typically required. Therefore, it is crucial to first understand the role of silver( i ) salts as additives, in order to wisely overcome this barrier and shift towards silver-free systems. This review discusses the important role of silver( i ) salts as additives in transition-metal catalyzed C-H activation, and depicts the discussion about the current shift towards Ag-free procedures, as plausible and sustainable alternatives.