Palladium-Catalyzed Electrophilic C-H-Bond Fluorination: Mechanistic Overview and Supporting Evidence

Palladium-catalyzed electrophilic fluorination is a particularly attractive and challenging synthetic issue. Because of the rapid evolution of this topic, a critical point on the mechanistic and experimental advances is provided herein. In the present review, we focused on current mechanistic understanding in electrophilic fluorination (and related halogenations) catalyzed by palladium, mainly with N-directing group. Our discussion is based on the well-characterized or calculated pertinent metal species and intermediates used for analyzing the plausible catalytic cycles. A particular effort has been devoted to gathering supporting data for the putative species involved in catalysis, such as mass data, NMR in solution (F-19, P-31) and X-ray structures, often supported by theoretical approaches. The cut-off of this review is March 2018.