Organocatalyzed Trifluoromethylation of Ketones and Sulfonyl Fluorides by Fluoroform under a Superbase System

Fluoroform (HCF₃, HFC-23) is a side product in the manufacture of polytetrafluoroethylene (Teflon). Despite its attractive properties, taming HCF₃ for trifluoromethylation is quite problematic owing to its low acidity and the lability of the naked trifluoromethyl carbanion generated from HCF₃. Herein we report the organic-superbase-catalyzed trifluoromethylation of ketones and arylsulfonyl fluorides by HCF₃. The reactions were carried out by using a newly developed “superbase organocatalyst system” consisting of catalytic amounts of P₄-tBu and N(SiMe₃)₃. A series of aryl and alkyl ketones were converted into the corresponding α-trifluoromethyl carbinols in good yields under the organocatalysis conditions in THF. The superbase organocatalytic system can also be applied to the trifluoromethylation of arylsulfonyl fluorides for biologically important aryl triflones in THF or DMF in good yields. Protonated P₄-tBu, H[P₄-tBu]⁺, is suggested to be crucial for the catalytic process. This new catalytic methodology using HCF₃ is expected to expand the range of synthetic applications of trifluoromethylation.