Hypervalent Iodine-Catalyzed Fluorination of Diene-Containing Compounds: A Computational Study

Studies have shown that the incorporation of fluorine into materials can improve their properties, but C-F bonds are not readily formed in nature. Although some researchers have studied the reaction of fluorinating alkenes catalyzed by hypervalent iodine, far too little attention has been paid to its reaction mechanism. This study aimed to explore the mechanism of the hypervalent iodine-catalyzed 1,4-difluorination of dienes. We found that the catalyst is favorable for the activation of C1=C2 double bonds through halogen bonds, and then two HFs interact with one F atom in the catalyst via hydrogen bonds, resulting in the cleavage of I-F bonds and the formation of [F-H∙∙∙F]^-. Subsequently, the catalyst interacts with C1, and the roaming [F-H···F]^- attacks C4 from the opposite side of the catalyst. After the fluorination step is completed, the nucleophile F^- substitutes the catalyst via the S_N2 mechanism. Our calculations demonstrated that the interaction between HF and F^- is favorable for the stabilization of the transition state within the fluorination process for which the presence of two HFs in the reaction is the best. We also observed that [F-H∙∙∙F]^- attacking C4 from the opposite side of the catalyst is more advantageous than attacking from the same side. This study therefore offers a novel perspective on the mechanism of the hypervalent iodine-catalyzed fluoridation of dienes.