Redox‐Neutral Tetrafluoroethylation of Aryl Alkynes with 1,1,2,2‐Tetrafluoroethane Sulfonic Acid Leading to α‐Tetrafluoroethylated Acetophenones

Abstract

The redox‐neutral tetrafluoroethylation of alkynes with 1,1,2,2‐tetrafluroroethanesulfonic acid (TFESA) and azobis(isobutyronitrile) (AIBN) proceeds via the formation of vinyl tetrafluoroethanesulfonates followed by a radical tetrafluoroethylation. Experimental and theoretical results support an intermolecular reaction.

Vicinal Difunctionalization of Alkenes Using Vinyl Triflates Leading to γ-Trifluoromethylated Ketones

“…Based on the result of the radical probe experiment and our previous work, 22,27,26 we show a plausible mechanism for the reaction in Figure 1. The thermal decomposition of AIBN generates isobutyronitrile radical A.…”

“…Then, we examined the scope of the reaction toward various vinyl triflates. As vinyl triflates can undergo facile hydrolysis during column chromatography on silica gel, we attempted one-pot reactions between alkynes and trifluoromethane­sulfonic acid (TfOH) to generate the vinyl triflates in situ . For that purpose, a dichloroethane solution of terminal alkyne 1a′ and TfOH was heated at 80 °C for 1 h, before AIBN and 1-octene were added and heating at 90 °C was continued for another 3 h. The desired product was obtained in 67% yield (Scheme ).…”

One-Pot Synthesis of CF3-Substituted Vinyl Trifluoromethanesulfonamides from Imines and Trifluoromethanesulfonic Anhydride

“…In 2017, we reported a radical trifluoromethylation of vinyl triflates using ketones and Tf 2 O in the presence of a base, which led to α-trifluoromethylated ketones (Scheme ). − In these reactions, the vinyl triflates act as the radical acceptor and the trifluoromethyl radical source. At the same time, Yuan and Li reported a radical trifluoromethylation of vinyl triflates with AgNO 3 /(NH 4 ) 4 S 2 O 8 .…”

“…Based on our previous work − and initial experiments we would like to propose a plausible mechanism in Figure . The reaction of 1 with Tf 2 O ( 2a ) and 2,4,6-TTBP gives vinyl trifluoromethanesulfonamide 3a (first step).…”

Recent Advances in Radical Reactions of Vinyl Triflates and Their Derivatives

“…We found that triflation and trifluoromethylation reactions proceeded efficiently by simply heating the alkyne, trifluoromethanesulfonic acid, and AIBN in dichloroethane. 19 A variety of commercially available perfluoroalkanesulfonic acids can be used in this reaction. For example, 1,1,2,2-tetrafluoroethanesulfonic acid (TFESA), 20 which can be easily synthesized from tetrafluoroethylene (TFE), can be used in a tetrafluoroethylation reaction (Scheme 11).…”