Quantitative Scale for the Trifluoromethylthio Cation-Donating Ability of Electrophilic Trifluoromethylthiolating Reagents

A new parameter, trifluoromethylthio cation-donating ability (Tt(+)DA), is introduced as a quantitative descriptor for the propensity of electrophilic trifluoromethylthiolating reagents to transfer a CF3S moiety in organic synthesis. The first Tt(+)DA scale of popular reagents has been established through DFT calculations. Excellent correlation has been identified between the Tt(+)DAs of N-SCF3-type reagents and the pKa of the corresponding acids, offering a powerful avenue for the rational design of novel reagents.