Bi-functional fluoroalkylation reagents: an introduction to halo-substituted 3-oxa-perfluoroalkanesulfonyl fluorides

X(CF2CF2)nOCF2CF2SO2F (X=I, Br, Cl; n=1, 2, 3, 4) are widely used fluoroalkylation reagents, which can incorporate 'heavy' fluorous tags into organic compounds. X(CF2CF2)nOCF2CF2SO2F have both sulfonyl and halo groups. They behave as bi-functional fluoroalkylation reagents. The cleavage of the C-I bonds of I(CF2CF2)nOCF2CF2SO2F by reductants (such as Na2S2O4, Zn), single electron transfer reagents and radical initiator systems (like Bz2O2, AIBN, and (t-BuO)2, or under UV and heat) gives, respectively, the sulfinatodehalogenated products, the hydrodehalogenated products, the homo-coupling products and the perfluoroalkylated products (if alkenes, alkynes or arenes were added). The functionalization of the sulfonyl groups (SO2F) of X(CF2CF2)nOCF2CF2SO2F by esterification, amidation, and fluorination affords the corresponding perfluoroalkanesulfonates, fluoroalkanesulfonamide, and perfluoroalkanes. In many cases, both the halo and sulfonyl groups of X(CF2CF2)nOCF2CF2SO2F are transformed. These transformations finally lead to hundreds of useful highly fluorinated materials, such as supper acids, catalysts, surfactants, ion-exchange resins, electrolytes, polymers, and dense ionic liquids. Furthermore, X(CF2CF2)nOCF2CF2SO2F have commendable advantages, such as the easy preparation, the wide range of substrate tolerance, the mild reaction condition, and the high yields of desired products, which make them very promising. This review briefly summarizes the synthesis, reactivity, and applications of these intriguing reagents.