Nucleophilic Trifluoromethylation of Carbonyl Compounds and Disulfides with Trifluoromethane and Silicon-Containing Bases

Provided that DMF (or another N,N-dialkylformamide) is present in the reaction medium, at least in a catalytic amount, fluoroform trifluoromethylates efficiently carbonyl compounds, even enolizable ones, when opposed to (TMS)₂N^- M⁺, generated in situ from N(TMS)₃ and M⁺ F^- or RO^- Na⁺. When F^- is used in a catalytic amount, silylated α-(trifluoromethyl)carbinols are obtained: in this case, the four-component system HCF₃/N(TMS)₃/catalytic F^-/catalytic DMF behaves like the Ruppert's reagent, especially as far as nonenolizable carbonyl compounds are concerned (CF₃SiMe₃ remains more efficient for enolizable carbonyl compounds). This process involves an adduct between DMF and ^-CF₃ which is the true trifluoromethylating agent. In the same way, fluoroform efficiently trifluoromethylates disulfides and diselenides when deprotonated with a strong base selected from t-BuOK or N(SiMe₃)₃/Me₄NF (or TBAT). t-BuOK is more adapted to the trifluoromethylation of aryl disulfides whereas N(SiMe₃)₃/F^- is well suited to that of aliphatic disulfides.