An Energetic Guide for Estimating Trifluoromethyl Cation Donor Abilities of Electrophilic Trifluoromethylating Reagents: Computations of X–CF3 Bond Heterolytic Dissociation Enthalpies
2016
Li, Man | Xue, Xiao-Song | Guo, Jinping | Wang, Ya | Cheng, Jin-Pei
This work established an energetic guide for estimating the trifluoromethyl cation-donating abilities (TC⁺DA) of electrophilic trifluoromethylating reagents through computing X–CF₃ bond (X = O, S, Se, Te, and I) heterolytic dissociation enthalpies. TC⁺DA values for a wide range of popular reagents were derived on the basis of density functional calculations (M06-2X). A good correspondence has been identified between the computed TC⁺DA values and the experimentally observed relative trifluoromethylating capabilities of the reagents. Substituent effects hold good linear free energy relationships on the TC⁺DAs of the most widely used reagents including Umemoto reagent, Yagupolskii–Umemoto reagent, and Togni reagents, which allow their trifluoromethylating capabilities to be rationally tuned by substituents and thus extend their synthetic utility. All the information disclosed in this work would contribute to future rational exploration of the electrophilic trifluoromethylation chemistry.
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