Copper‐Catalyzed Remote C(sp3)−H Trifluoromethylation of Carboxamides and Sulfonamides

From a distance: Chemoselective trifluoromethylation of unactivated C(sp³)−H bonds distal to the functional group was achieved under mild, copper‐catalyzed conditions. A radical mechanism involving 1,5‐hydrogen atom transfer of N‐radicals followed by CF₃‐transfer from Cu^II−CF₃ complexes to the thus formed alkyl radicals is proposed.

Abstract

Reported herein is an unprecedented protocol for trifluoromethylation of unactivated aliphatic C(sp³)−H bonds. With Cu(OTf)₂ as the catalyst, the reaction of N‐fluoro‐substituted carboxamides (or sulfonamides) with Zn(CF₃)₂ complexes provides the corresponding δ‐trifluoromethylated carboxamides (or sulfonamides) in satisfactory yields under mild reaction conditions. A radical mechanism involving 1,5‐hydrogen atom transfer of N‐radicals followed by CF₃‐transfer from Cu^II−CF₃ complexes to the thus formed alkyl radicals is proposed.

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