Hypervalent Iodine-Mediated Fluorination: Development of Catalytic and Stoichiometric Fluorination Reactions

Hypervalent iodine reagents have been recognized as useful and environmentally benign reagents, and widely used in organic synthesis. Among them, (difluoroiodo) arenes and Togni's reagents are stable, low toxic, and have attracted much attention as useful fluorinating reagents because they can reduce the drawbacks found in direct fluorination reactions with fluorine gas. However, most (difluoroiodo) arenes are prepared by reaction of iodosylarenes with HF reagents. For the fluorination reaction, in addition, (difluoroiodo) arenes must be activated by a HF reagent such as HF. amine complexes. Accordingly, HF is essential both for the preparation and for the activation of ArIF2 in the fluorination reaction. To avoid such tedious procedures and develop a convenient method, we envisaged one-pot fluorination reactions achieving both preparation of a (difluoroiodo) arene and its activation for fluorination. In the fluorination reaction, HF is considered to play two roles as the reagent for the generation of ArIF2 and as the activating agent for the fluorination reaction. Using a convenient fluorinating reagent composed of a hypervalent iodine compound and a HF source, we conducted the following reactions: (1) selective fluorination of carbonyl compounds such as 1,3-diketones, beta-ketoesters, beta-ketoamides, malonic esters and aromatic ketones, and (2) gem-difluorination of styrenes. The detailed results are reported.