Copper‐Catalyzed Trifluoromethylation of Aliphatic <i>N</i>‐Arylhydrazones: A Concise Synthetic Entry to 2‐Trifluoromethylindoles from Simple Aldehydes

Abstract

Abstract The copper‐catalyzed C( sp 2 )H trifluoromethylation of N,N ‐disubstituted hydrazones using the Togni reagent is demonstrated to proceed efficiently for aliphatic aldehyde‐derived substrates. The success of the reactions relied on the choice of the N,N ‐diphenylamino group as the terminal hydrazone amino group where N,N ‐dialkylamino groups were preferred for (hetero)aromatic aldehyde‐derived substrates. In addition, the trifluoromethylated N ‐arylhydrazones are shown to be ideal substrates for Fischer indole synthesis allowing a straightforward, three‐step access to 2‐trifluoromethylindole derivatives from simple aldehydes. magnified image