In this review, we highlight the recent progress of transition-metal-catalyzed fluorination and trifluoromethylation reported between 20. However, until now, no comprehensive survey of the literature has been reported on this topic. Recently, Zhang offered a brief summary of the recent achievements in the ever-growing field of green fluoroalkylation. Then, Toste covered advances in catalytic enantioselective fluorination, mono‑, di‑, and trifluoromethylation, and trifluoromethylthiolation reactions. Kamlet mainly discussed progresses in catalyzed fluorination and trifluoromethylation before 2011, and Besset focused on the direct introduction of fluorinated groups into alkenes and alkynes. Over the past few years, several reviews on fluorination/fluoroalkylation have disclosed. Meanwhile, other transition metals, such as Fe, Ni, Rh, Ag, Co, etc., have received considerable attention and are widely applied due to their respective characteristics. In addition, among the various metals developed, palladium is the most commonly employed transition metal, followed by copper owing to its high efficiency and cheapness. Therefore, transition-metal-catalyzed fluorination/fluoroalkylation reactions represent an important and hot topic in fluorine chemistry. Furthermore, transition metals have the unique advantage of possessing multiple mechanistic features, which translates into the ability to apply new substrate classes and provide hitherto novel and inaccessible structures. In this regard, the use of various transition metals to catalyze the synthesis of organic fluorides has become a mature field, and the application of these methodologies has allowed decreasing the need of pre-functionalized substrates, less consumption of reaction time and costs, and enabled to produce enantioenriched target compounds. Also, low functional group tolerance, being limited to activated arenes, the production of metal salts as stoichiometric byproducts, and poor levels of regioselectivity would always be observed, limiting the progress of fluorine chemistry to some extent. However, traditional fluorination methods to these building blocks, such as Friedel–Crafts-type electrophilic halogenation, Sandmeyer-type reactions of diazonium salts, and halogenations of preformed organometallic reagents, commonly involve multiple steps, harsh reaction conditions, and the use of stoichiometric amounts and/or toxic reagents. Therefore, it is highly desirable to introduce a fluorine-containing substituent into a molecule artificially. Īlthough the content of fluorine in the Earth’s crust is relatively abundant (13th most abundant element), scientists have identified only 21 kinds of fluorine-containing natural molecules. According to statistics, about 35% of agrochemicals and 20% of pharmaceuticals contain fluorine. Consequently, carbon–fluorine bonds have become an integral part of pharmaceutical, agricultural, materials industries, and tracers for positron emission tomography. Due to these unique properties, the introduction of fluorine into a molecule can cause dramatic changes, such as the acidity or basicity of neighboring groups, dipole moment, and properties such as lipophilicity, metabolic stability, and bioavailability. Compared with other halogens (Cl, Br, I), fluorine (F) has completely different physical and chemical properties, such as a unique electronic structure, strongest electronegativity, and small atomic radius similar to that of hydrogen atoms.
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