Fluorination of styrene derivatives with a reagent system composed of μ-oxo-bis[trifluoroacetato(phenyl)iodine] and a pyridine·HF complex gave the corresponding (2,2-difluoroethyl)arenes in good yields. Similarly, the reagent of PhI(OCOCF3)2 and the pyridine·HF complex acted as a fluorinating agent for styrene derivatives. The fluorination of styrene derivatives with the pyridine·HF complex underwent under catalytic conditions using 4-iodotoluene as a catalyst and m-CPBA as a terminal oxidant.

The intramolecular aminofluorination of homoallylamine derivatives using a reagent system of PhI(OAc) and Py·HF in CHCl at room temperature for 5 h gave N-tosyl-3-fluoropyrrolidines in good to high yields. Furthermore, the catalytic aminofluorination was furnished by the reaction using p-iodotoluene as a catalyst in the presence of Py·HF as a fluorine source and mCPBA as a terminal oxidant.

The direct fluorination reaction of acetophenone using iodosylarenes and TEA·5HF was conducted under mild conditions except for use of a HF reagent. The fluorination reaction was applied to acetophenone derivatives, acetonaphthones, benzyl phenyl ketone, propiophenone, butyrophenone, 1-indanone, and phenacyl chloride, giving selectively the corresponding α-fluoroketone derivatives in good yields.

Direct fluorination of 1,3-dicarbonyl compounds including 1,3-diketones, 3-oxo esters, and 3-oxoamides was conducted using aqueous hydrofluoric acid with the aid of iodosylarenes, giving the corresponding 2-fluorinated products in good to high yields. Among the used iodosylarenes, o-iodosyltoluene was found to be the most effective, and the yield of 2-fluorinated products was improved.Organofluorine compounds have attracted much attention, since they are applicable to pharmaceuticals, agrochemicals and functional materials due to their unique properties. There are two major processes for the synthesis of organofluorine compounds: 1 (a) direct replacement of an atom or group by a fluorine atom and (b) indirectly using a fluorinated component as a building block. Since the fluorinated building blocks are prepared by direct fluorination, the development of methods for the introduction of fluorine atoms remains important. Although direct fluorination reactions have been conducted using molecular fluorine or other electrophilic fluorinating reagents, some drawbacks remain, namely the possibility of explosion due to instability, difficulty of handling, and the requirement for specific apparatus. Recent remarkable progress in the chemistry of hypervalent iodine compounds has been proven that hypervalent iodine compounds are useful in organic synthesis. 2 (Difluoroiodo)arenes (ArIF 2 ) are stable and low toxic, and they have attract much attention as useful reagents because they can reduce the drawbacks found in direct fluorination reactions. 3 However, most (difluoroiodo)arenes are prepared by fluorination of iodoarenes with powerful fluorinating reagents, such as fluorine 4 or xenon difluoride, 5 they are conveniently prepared by direct replacement in (dichloroiodo)arenes with hydrogen fluoride in the presence of mercury(II) oxide, 6 and they are more simply prepared by reaction of iodosylarenes with hydrofluoric acid. 7 In addition, (difluoroiodo)arenes must be activated by a hydrofluoric acid reagent such as hydrofluoric acidamine complexes for fluorination reactions. 3,8 Accordingly, hydrofluoric acid is essential for both the preparation and activation of (difluoroiodo)arenes in fluorination reactions. To develop a convenient one-pot fluorination reaction, we envisaged achieving both the preparation of a (difluoroiodo)arene and its activation for fluorination. In the fluorination reaction, aqueous hydrofluoric acid was considered to play both roles: (1) as the reagent for the generation of the (difluoroiodo)arene and (2) as the activating agent for the fluorination reaction, as shown in Scheme 1.

The reaction of alkynes with PhIO and Py·HF followed by treatment with BF·OEt gave β-fluorovinyliodonium tetrafluoroborates in good to high yields. More conveniently, the reaction using PhI and Py·HF in the presence of m-CPBA also afforded β-fluorovinyliodonium tetrafluoroborates in good yields. These methods have the advantages that β-fluorovinyliodonium salts can be prepared without ArIF.