A fluorinating hypervalent iodine(III) reagent: 4-Iodotoluene difluoride

(A) Reacting α-phenylsulfanylated esters5 and amides 6 with 1 equiv of 1 led to α-monofluoro sulfides via a fluoro-Pummerer reaction. α-Selenocarboxylic acid derivatives could be easily α-monofluorinated via a similar Pummerer reaction.4 (Chemical Equation Presented) (B) Hara and co-workers achieved α-fluorinated monoketones using the corresponding silyl enol ethers as substrates.7 (Chemical Equation Presented) (C) The α-monofluorination of β-keto esters, amides, and ketones was easily accomplished using 1, overcoming the problematic use of amine-HF complexes. 8 However, the fluorination under these conditions is slower than that using an acid medium.9 (Chemical Equation Presented) (D) The preparation of vicinal difluoroalkanes was achieved reacting aliphatic alkenes with 1. (Chemical Equation Presented) (E) The behavior of cyclic alkenes towards 1 can be different from the acyclic variant because a fluorinative and diastereoselective ring-contraction reaction may take place.10 (Chemical Equation Presented) (F) Unsaturated alcohols and acids are fluorocyclized when treated with 1 in the presence of amine-HF complexes and afford cyclic ethers and lactones with poor or no stereoselectivity, respectively.11 (Chemical Equation Presented) (G) (E)-β-Fluoroalkenyliodonium salts were prepared regio- and stereoselectively by Hara and co-workers from the corresponding terminal alkynes and 1 without using 5HF·Et3N.12 These compounds could be subsequently used in Pd-catalyzed cross-coupling reactions 12,13 or Pd-catalyzed carbomethoxylation.14 (Chemical Equation Presented) (H) Alkynes and alkenes undergo phenylselenofluorination in the presence of 1 and PhSeSePh in high stereo- and regioselectivity. 15 Analogously, when iodine instead of PhSeSePh is empoyed, iodofluorination of alkenes and alkynes affords fluoroiodoalkanes and fluoroiodoalkenes.16 (Chemical Equation Presented) (I) Iodoalkanes give the corresponding alkyl fluoride when treated with 1 in the presence of amine-HF complexes, via an iodonium intermediate.17 (Chemical Equation Presented) (J) Stereoselective ring expansion of iodine-containing 4-, 5-, and 6-membered cyclic ethers took place using 1, affording 5-, 6-, and 7-membered cyclic fluoro ethers.18 (Chemical Equation Presented). © Georg Thieme Verlag Stuttgart.